KR102394159B1 - Electrode, method for producing said electrode, electricity storage device provided with said electrode, and conductive carbon mixture for electricity storage device electrode - Google Patents

Abstract

An electrode is provided which imparts an electrical storage device having a high energy density and good cycle life. The electrode for a power storage device of the present invention comprises an electrode active material particle and an active material layer containing paste-like conductive carbon derived from oxidation-treated carbon that has been subjected to oxidation treatment to a carbon raw material having voids covering the surface of the electrode active material particle. It is an electrode characterized in that it has. Since the paste-like conductive carbon derived from the oxidized carbon is densely filled not only in the gaps formed between the active material particles but also into the pores existing on the surface of the active material particles, the electrode density increases, so the energy of the electrical storage device density is improved. Moreover, since paste-form conductive carbon suppresses melt|dissolution of an active material, the cycling characteristics of an electrical storage device improve.

Description

An electrode, the manufacturing method of this electrode, the electrical storage device provided with this electrode, and the conductive carbon mixture for electrical storage device electrodes TECHNICAL FIELD }

The present invention relates to an electrode providing a power storage device having a high energy density and good cycle life. This invention also relates to the manufacturing method of this electrode, and the electrical storage device provided with this electrode. This invention also relates to the conductive carbon mixture used in manufacture of the electrode of an electrical storage device.

Power storage devices such as secondary batteries, electric double layer capacitors, redox capacitors and hybrid capacitors are used as power sources for information devices such as mobile phones and notebook computers, motor driving power sources for low-emission vehicles such as electric and hybrid vehicles, and energy regeneration systems. Although the device is widely studied for this purpose, in order to meet the request|requirement of performance improvement and miniaturization in these power storage devices, the improvement of energy density and cycle life is desired.

In these electrical storage devices, an electrode active material that expresses capacity by a Faraday reaction involving transfer of electrons with ions in an electrolyte (including an electrolyte solution) or a non-Faraday reaction without electron transfer is used for energy storage. . And, these active materials are generally used in the form of a composite material with a conductive agent. As a conductive agent, conductive carbons, such as carbon black, natural graphite, artificial graphite, and a carbon nanotube, are normally used. These conductive carbons play a role in imparting conductivity to the composite material when used in combination with an active material with low conductivity, but also act as a matrix to absorb the volume change caused by the reaction of the active material, and even if the active material is mechanically damaged, electrons It also plays a role of securing a conduction path.

By the way, the composite material of these active materials and conductive carbon is generally manufactured by the method of mixing the particle|grains of an active material, and conductive carbon. Since conductive carbon does not fundamentally contribute to the improvement of the energy density of an electrical storage device, in order to obtain the electrical storage device which has a high energy density, it is necessary to reduce the amount of conductive carbon per unit volume and to increase the amount of active materials. Then, by improving the dispersibility of conductive carbon or reducing the structure of conductive carbon, the distance between active material particles is made close, and examination which increases the amount of active material per unit volume is performed.

For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-134304) contains a carbon material with a small particle diameter (acetylene black in the example) having an average primary particle diameter of 10 to 100 nm, and a blackening degree of 1.20 or more. A non-aqueous secondary battery having a positive electrode having The paint used for preparing the positive electrode is a high-speed rotating homogenizer-type disperser, a high-speed rotating homogenizer-type disperser, or a high shear dispersion device such as a planetary mixer having three or more rotating shafts, or It is obtained by adding and further dispersing the dispersion in which the mixture of the carbon material, the binder, and the solvent is dispersed by a strong shear dispersing device to the paste in which the mixture of the positive electrode active material, the binder, and the solvent is dispersed. By using an apparatus having a strong shear force, the carbon material, which is difficult to be dispersed due to a small particle diameter, is uniformly dispersed.

In addition, Patent Document 2 (Japanese Patent Application Laid-Open No. 2009-35598) discloses a non-aqueous secondary battery comprising acetylene black having a BET specific surface area of 30 to 90 m 2 /g, a DBP absorption amount of 50 to 120 mL/100 g, and a pH of 9 or more. A conductive agent for an electrode is disclosed. The electrode of a secondary battery is comprised by dispersing this mixture of acetylene black and an active material in the liquid containing a binder, preparing a slurry, and apply|coating and drying this slurry on an electrical power collector. Acetylene black having the above characteristics has a lower structure than Ketjen black or conventional acetylene black, so the bulk density of the mixture with the active material is improved, and the battery capacity is improved.

Moreover, by coat|covering a part or all of the surface of an active material particle with conductive carbon particle, the uniform distribution state of an active material and conductive carbon is created, the electroconductivity between active materials is improved, and prevention of the fall of cycle life is also examined. For example, in Patent Document 3 (Japanese Patent Laid-Open No. 11-283623), mother particles of a lithium composite oxide such as LiCoO ₂ acting as an active material and child particles of a carbon material such as acetylene black acting as a conductive agent are described. A method of covering a part or all of the surface of a mother particle of a composite oxide with child particles of a carbon material by mixing while applying compression and shearing action, and the composite material obtained by this method is used for a positive electrode of a non-aqueous secondary battery is disclosed.

Japanese Patent Laid-Open No. 2004-134304 Japanese Patent Laid-Open No. 2009-35598 Japanese Patent Laid-Open No. 11-283623

Although the further improvement of energy density is always requested|required of an electrical storage device, as a result of the inventors examining, even if it is a method similar to patent document 1 or patent document 2, it is difficult to make conductive carbon enter effectively between active material particles, Therefore, between active material particles It was difficult to increase the amount of active material per unit volume by making the distance closer. Therefore, there existed a limit in the improvement of the energy density by the positive electrode and/or a negative electrode using the composite material of active material particle and conductive carbon. In addition, the method of coating the surface of the active material particles with carbon particles as in Patent Document 3 also has a limit to the improvement of the energy density, and is sufficiently satisfied due to the causes such as dissolution of the active material in the electrolyte of the non-aqueous secondary battery. No cycle life was obtained.

Therefore, it is an object of the present invention to provide an electrode which imparts an electrical storage device having a high energy density and good cycle life.

As a result of intensive studies, the inventors have found that the above object is achieved when an electrode of a power storage device is constituted using an electrode material containing an active material particle and oxidation-treated carbon obtained by subjecting a carbon raw material having voids to a strong oxidation treatment, completed the invention.

Therefore, the present invention is a paste-like (paste-like) derived from oxidation-treated carbon obtained by oxidizing an electrode active material particle as an electrode for a power storage device, and a carbon raw material having voids covering the surface of the electrode active material particle. It has an active material layer containing conductive carbon of ), It relates to the electrode characterized by the above-mentioned. The voids include internal voids of Ketjen black, voids within tubes of carbon nanofibers or carbon nanotubes, and voids between tubes, in addition to voids of the porous carbon powder. In addition, in the SEM photograph taken at a magnification of 25000 times, "paste phase" means a state in which the grain boundaries of primary carbon particles are not confirmed and non-particulate amorphous carbon is connected.

Oxidation-treated carbon obtained by oxidizing the carbon raw material having voids tends to adhere to the surface of the active material particles. In addition, oxidation-treated carbon subjected to strong oxidation treatment is compressed integrally when subjected to pressure, spreads in a paste-like form, and is not easily scattered. Therefore, when an electrode material is obtained by mixing active material particles with oxidation-treated carbon that has been subjected to strong oxidation treatment for an electrode of a power storage device, in the process of mixing, oxidation-treated carbon adheres to the surface of the active material particles and covers the surface, thereby dividing the active material particles. Improves acidity. In addition, due to the pressure exerted on the oxidation-treated carbon in the process of mixing, at least a part of the oxidation-treated carbon spreads in a paste-like form so that the surface of the active material particles is partially covered. Then, when an active material layer is formed using this electrode material on the current collector of the electrode and pressure is applied to the active material layer, the oxidation-treated carbon, at least a part of which has been changed to a paste form, further spreads, covering the surface of the active material particles and densifying the active material. As the particles approach each other, the oxidation-treated carbon changed to a paste-like form covers the surface of the active material particles, and not only the gaps formed between the adjacent active material particles, but also the pores (in the secondary particles) on the surface of the active material particles. It is also extruded and densely filled inside (including the gap between the primary particles identified in the present invention) (see FIG. 2). Therefore, the amount of active material per unit volume in an electrode increases, and an electrode density increases. In addition, the densely filled paste-like oxidation-treated carbon has sufficient conductivity to function as a conductive agent. In addition, the electrode of the present invention may contain oxidized carbon that is not changed into a paste.

In a preferred embodiment of the electrode of the present invention, the paste-like conductive carbon derived from oxidation-treated carbon has a width of 50 nm or less and is present in the gap formed between adjacent electrode active material particles and/or on the surface of the electrode active material particles. It is also present inside the hole. Therefore, the coverage of the surface of the active material particle by paste-form conductive carbon improves, the electroconductivity of the whole active material layer improves, and an electrode density improves. In addition, the "width of the gap formed between the electrode active material particles" means the shortest distance among the distances between adjacent active material particles, and "the width of the hole existing on the surface of the electrode active material particle" means between the points where the openings of the holes face each other. means the shortest distance among the distances.

Although the electrode of this invention has the active material layer containing the paste-form conductive carbon with which it filled densely, it turns out that the impregnation with respect to the electrode inside of the electrolyte solution in an electrical storage device is not suppressed. In the preferred aspect of the electrode of the present invention, when the pore distribution of the active material layer of the electrode is measured by the mercury intrusion method, it is found that the active material layer has pores having a diameter of 5 to 40 nm. These micropores are mainly derived from oxidation-treated carbon and are considered to be pores in the densified paste-like conductive carbon, but it is a sufficient size for the electrolytic solution in the electrical storage device to pass through the paste-like conductive carbon to reach the active material particles. Therefore, the paste-form conductive carbon in an electrode has sufficient electroconductivity and does not suppress the impregnation of the electrolyte solution in an electrical storage device. As a result, the improvement of the energy density of an electrical storage device is brought about.

Moreover, in the active material layer of the electrode of this invention, it is thought that it is because the surface of an active material particle is coat|covered with the conductive carbon which spreads densely and paste-like up to the inside of the hole which exists in the surface of an active material particle, but this invention When a power storage device is constructed using an electrode of

It is preferable that the oxidation-treated carbon which provides the said paste-form conductive carbon contains a hydrophilic part, and content of the hydrophilic part is 10 mass % or more of the whole oxidation-treated carbon. Here, the "hydrophilic moiety" of carbon has the following meanings. That is, 0.1 g of carbon is added to 20 mL of an aqueous ammonia solution having a pH of 11, and the resultant solution is subjected to ultrasonic irradiation for 1 minute, and the resulting solution is left to stand for 5 hours to precipitate a solid portion. A portion that is not precipitated and is dispersed in an aqueous ammonia solution having a pH of 11 is a “hydrophilic portion”. In addition, content with respect to the whole carbon of a hydrophilic part is calculated|required by the following method. After precipitation of the solid portion, the remaining portion from which the supernatant is removed is dried, and the weight of the dried solid is measured. The weight obtained by subtracting the weight of the solid after drying from the weight of 0.1 g of the initial carbon is the weight of the "hydrophilic part" dispersed in the aqueous ammonia solution having a pH of 11. Incidentally, the weight ratio of the weight of the “hydrophilic portion” to the weight of 0.1 g of the first carbon is the content of the “hydrophilic portion” in the carbon.

The ratio of the hydrophilic part in conductive carbons, such as carbon black, natural graphite, and carbon nanotube, used as a conductive agent in the electrode of the conventional electrical storage device is 5 mass % or less of the whole. However, when carbon having voids is used as a raw material and these raw materials are subjected to oxidation treatment, they are oxidized from the surface of the particles, and hydroxyl groups, carboxyl groups or ether bonds are introduced into the carbon, and the conjugated double bonds of carbon are oxidized and single carbon bonds are oxidized. is formed, and the carbon-carbon bond is partially cleaved to generate a hydrophilic moiety on the particle surface. And when the intensity|strength of an oxidation treatment is strengthened, the ratio of the hydrophilic part in a carbon particle will increase, and a hydrophilic part will occupy 10 mass % or more of the whole carbon. In addition, such oxidation-treated carbon is integrally compressed when subjected to pressure and easily spreads in a paste form, covering most or all of the surface of the active material particles up to the inside of the pores existing on the surface of the active material particles, and is easy to densify . As a result, 80% or more, preferably 90% or more, particularly preferably 95% or more of the surface (outer surface) of the active material particles in the active material layer of the electrode is derived from oxidation-treated carbon and is in contact with the densified paste-like conductive carbon. A working electrode is obtained. In addition, the coverage of the surface of the active material particle by paste-form conductive carbon is the value computed from the SEM photograph which image|photographed the cross section of the active material layer at 25000 times magnification.

In the electrode for a power storage device of the present invention, the electrode active material particles in the active material layer are microparticles having an average particle diameter of 0.01 to 2 μm that can operate as a positive electrode active material or a negative electrode active material, and two that can operate as the same active material as the microparticles. It is preferable to consist of coarse particles having an average particle diameter of greater than ㎛ and not greater than 25 ㎛. The coarse particles themselves improve the electrode density, and also have the action of preferably pressing the oxidized carbon at the time of electrode material manufacturing and electrode manufacturing, rapidly changing the oxidized carbon into a paste form, and densifying the electrode density. to increase the energy density of the power storage device. In addition, gaps formed between the adjacent coarse particles together with the oxidation-treated carbon spread in a paste-like state while the fine particles press the oxidized carbon in which at least a part of the paste-formed carbon is pressed by the pressure applied to the active material layer during electrode manufacturing. Since it is extruded to and filled with, the electrode density further increases, and the energy density of the electrical storage device further improves. In addition, the average particle diameter of active material particle|grains means the 50% diameter (median diameter) in the measurement of the particle size distribution using the light-scattering particle size meter.

The electrode for electrical storage devices of this invention WHEREIN: It is preferable that the conductive carbon which has higher electrical conductivity than other conductive carbon, especially the paste-form conductive carbon derived from oxidation-treated carbon is further contained in an active material layer. By the pressure applied to the active material layer during electrode manufacturing, these carbons are also coated on the paste-form conductive carbon, and the gaps formed by the active material particles adjacent to the paste-form conductive carbon are filled with gaps to improve the conductivity of the active material layer. Therefore, the energy density of the power storage device is further improved.

The electrode for electrical storage devices of this invention WHEREIN: It is preferable that mass ratio of the electrode active material particle in an active material layer, and conductive carbon is the range of 95:5 - 99:1. When other conductive carbon is contained in addition to the paste-like conductive carbon derived from the oxidation-treated carbon, the mass ratio of these total amounts and electrode active material particle|grains is the above-mentioned range. When the ratio of conductive carbon is less than the said range, the electroconductivity of an active material layer runs short, the coverage of the active material particle by conductive carbon falls, and there exists a tendency for cycling characteristics to fall, When the ratio of conductive carbon is more than the said range, electrode The density decreases and the energy density of the electrical storage device tends to decrease.

As described above, the electrode for a power storage device of the present invention,

By mixing electrode active material particles and carbon raw material having voids with oxidation-treated carbon subjected to oxidation treatment, at least a part of the oxidation-treated carbon is changed to a paste-like form to prepare an electrode material adhering to the surface of the electrode active material particles , and

A pressing step of forming an active material layer on a current collector with the electrode material and applying pressure to the active material layer

It can be preferably prepared by a method comprising a. Accordingly, the present invention also relates to a method for manufacturing this electrode.

When the active material layer contains conductive carbon having higher electrical conductivity than other conductive carbons, particularly conductive carbons derived from paste-like conductive carbon derived from oxidation-treated carbon, the above preparation step is

By dry-mixing the oxidation-treated carbon and the other conductive carbon, at least a portion of the oxidation-treated carbon is changed to a paste-like form to obtain a conductive carbon mixture adhering to the surface of the other conductive carbon, and

By dry-mixing or wet-mixing the conductive carbon mixture and the electrode active material particles, attaching the oxidation-treated carbon, in which at least a portion is changed into a paste, also to the surface of the electrode active material particles

It is preferable to carry out by a method comprising a.

Since the fine carbon particles have poor compatibility with the binder and the solvent, when preparing the electrode material in the form of a slurry containing the binder and the solvent, as described above with respect to Patent Documents 1 and 2, a strong shear dispersion device is used. In general, it is common to wet-mix the mixture or dry-mix the electrode active material particles and carbon, then add a binder and a solvent to wet-mix, but the conductive carbon mixture has a high electrode density regardless of the mixing method of the mixture and the electrode active material particles. In addition, an electrode having excellent conductivity is provided. Accordingly, the present invention further relates to a conductive carbon mixture for manufacturing an electrode of an electrical storage device, which is derived from oxidation-treated carbon obtained by subjecting a carbon raw material having voids to oxidation treatment, at least partly paste-like conductive carbon and the oxidation-treated carbon Other conductive carbon is included, and said at least one part has paste-form conductive carbon adhering to the surface of the said other conductive carbon, It is related with the conductive carbon mixture characterized by the above-mentioned.

The electrode of the present invention provides a power storage device having a high energy density and good cycle life. Accordingly, the present invention also relates to a power storage device provided with the electrode.

(Effects of the Invention)

In the electrode of the present invention having an active material layer comprising an electrode active material particle and a paste-like conductive carbon derived from an oxidation-treated carbon that has been subjected to oxidation treatment to a carbon raw material having voids covering the surface of the electrode active material particle, Since the paste-like conductive carbon derived from oxidation-treated carbon is densely filled not only in the gaps formed between the active material particles but also into the pores existing on the surface of the active material particles, the amount of active material per unit volume in the electrode increases and the electrode density increases. Moreover, while having the electroconductivity sufficient to function as a electrically conductive agent, the paste-form conductive carbon filled densely does not suppress the impregnation of the electrolyte solution in an electrical storage device. As a result, the improvement of the energy density of an electrical storage device is brought about. Moreover, in the electrode of this invention, it is thought that it is because the paste-form conductive carbon has coat|covered the surface of an active material particle to the inside of the hole which exists in the surface of an active material particle, but an electrical storage device is comprised by the electrode of this invention When it does, dissolution of the active material with respect to the electrolyte solution in an electrical storage device is suppressed, and the cycling characteristic of an electrical storage device improves.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the relationship between the content of the hydrophilic part of oxidation-treated carbon, and electrode density about the electrode of an Example and a comparative example.
2 is a SEM photograph of a cross-section of the electrode of Example, (A) is a photograph at 1500 magnification, and (B) is a photograph at 25000 magnification.
3 is an SEM photograph of a cross-section of an electrode of a comparative example, (A) is a photograph at 1500 magnification, and (B) is a photograph at 25000 magnification.
FIG. 4 is a view showing the result of measuring the pore distribution by the mercury intrusion method for the electrodes shown in FIGS. 2 and 3 .
5 is a diagram showing the rate characteristics of a lithium ion secondary battery provided with an electrode of an Example or Comparative Example.
6 is a view showing cycle characteristics of the lithium ion secondary battery showing the rate characteristics in FIG. 5 .
7 is a view showing the rate characteristics of a lithium ion secondary battery provided with an electrode of an Example or Comparative Example.
8 is a view showing cycle characteristics of the lithium ion secondary battery showing the rate characteristics in FIG. 7 .
9 is a diagram showing the rate characteristics of a lithium ion secondary battery provided with an electrode of an Example or Comparative Example.
FIG. 10 is a view showing cycle characteristics of the lithium ion secondary battery having the rate characteristics shown in FIG. 9 .
Fig. 11 is an SEM photograph of 50000 times a mixture obtained by dry-mixing particles of oxidation-treated carbon, acetylene black, and active material.
12 is a diagram showing the rate characteristics of a lithium ion secondary battery provided with an electrode of an Example or Comparative Example.
13 is a view showing cycle characteristics of the lithium ion secondary battery showing the rate characteristics in FIG. 12 .
Fig. 14 is an SEM photograph at 50000 times of a mixture obtained by dry-mixing oxidation-treated carbon or acetylene black and fine particles of an active material.
Fig. 15 is a SEM photograph of 100000 times a mixture obtained by dry-mixing oxidation-treated carbon or acetylene black and coarse particles of the active material.
It is a SEM photograph of 50000 times of a conductive carbon mixture.
Fig. 17 is a TEM photograph of the conductive carbon mixture, (A) is a photograph at a magnification of 100000, and (B) is a photograph at a magnification of 500000.
18 is a 25000-fold SEM photograph of the cross-section of the electrode of the embodiment prepared using the conductive carbon mixture.
19 is a view showing the result of measuring the DC internal resistance of the lithium ion secondary battery using the electrode of Example or Comparative Example.

The electrode for a power storage device of the present invention comprises an electrode active material particle and an active material layer containing paste-like conductive carbon derived from oxidation-treated carbon that has been subjected to oxidation treatment to a carbon raw material having voids covering the surface of the electrode active material particle. have First, the oxidation-treated carbon before changing to a paste form is demonstrated, and then the electrode of this invention and the electrical storage device using this electrode are demonstrated.

(1) Oxidized carbon

In the electrode of the present invention, the oxidation-treated carbon for imparting paste-like conductive carbon contained in the active material layer is carbon having pores such as porous carbon powder, Ketjen black, furnace black having pores, carbon nanofibers and carbon nanotubes. It is manufactured as a raw material. As the carbon raw material, carbon having pores with a specific surface area of 300 m 2 /g or more as measured by the BET method is preferably used because oxidation-treated carbon that is easily changed to a paste-like form by oxidation treatment is preferred. Among them, particularly preferred are spherical particles such as Ketjen black or furnace black having voids. Even if it oxidizes using solid carbon as a raw material, it is difficult to obtain the oxidation-treated carbon which changes to a paste form.

For the oxidation treatment of the carbon raw material having voids, a known oxidation method can be used without particular limitation. For example, oxidation-treated carbon can be obtained by treating the carbon raw material in an acid or hydrogen peroxide solution. As the acid, nitric acid, a mixture of nitric acid and sulfuric acid, an aqueous hypochlorous acid solution, and the like can be used. Further, oxidation-treated carbon can be obtained by heating the carbon raw material in an oxygen-containing atmosphere, water vapor, or carbon dioxide. Furthermore, oxidation-treated carbon can be obtained by plasma treatment, ultraviolet irradiation, corona discharge treatment, or glow discharge treatment in an oxygen-containing atmosphere of the carbon raw material.

When a carbon raw material having voids is subjected to oxidation treatment, it is oxidized from the surface of the particles and a hydroxyl group, carboxy group or ether bond is introduced into the carbon, and a conjugated double bond of carbon is also oxidized to form a carbon single bond, partially between carbons. The bond is cleaved to create a hydrophilic-rich moiety on the particle surface. The oxidation-treated carbon having such a hydrophilic moiety tends to adhere to the surface of the active material particles and effectively suppresses aggregation of the active material particles. Then, if the strength of the oxidation treatment is strengthened, the proportion of the hydrophilic portion in the carbon particles increases to obtain the oxidation-treated carbon that changes to a paste form during the electrode manufacturing process. It is preferable that content of the hydrophilic part in oxidation-treated carbon is 10 mass % or more of the whole oxidation-treated carbon. It is especially preferable that content of a hydrophilic part is 12 mass % or more and 30 mass % or less of the whole.

Oxidation-treated carbon containing 10% by mass or more of the total hydrophilic portion,

(a) a step of treating the carbon raw material having pores with an acid;

(b) mixing the product after acid treatment with the transition metal compound;

(c) pulverizing the obtained mixture and generating a mechanochemical reaction;

(d) heating the product after the mechanochemical reaction in a non-oxidizing atmosphere, and

(e) a step of removing the transition metal compound and/or its reaction product from the product after heating

It can be preferably obtained by a manufacturing method comprising

In the step (a), a carbon raw material having voids, preferably Ketjen Black, is immersed in acid and allowed to stand. You may irradiate an ultrasonic wave at the time of this immersion. As the acid, an acid commonly used for oxidation treatment of carbon, such as nitric acid, a mixture of nitric acid and sulfuric acid, and an aqueous hypochlorous acid solution can be used. The soaking time depends on the concentration of the acid, the amount of the carbon raw material to be treated, and the like, but is generally in the range of 5 minutes to 5 hours. After the carbon after acid treatment is sufficiently washed with water and dried, it is mixed with a transition metal compound in step (b).

(b) Examples of the transition metal compound added to the carbon raw material in the step include inorganic metal salts such as halides, nitrates, sulfates and carbonates of transition metals, formates, acetates, oxalates, methoxides, ethoxides, and isopropoxides. Organometallic salts, such as a seed, or a mixture thereof can be used. These compounds may be used independently and may mix and use 2 or more types. A compound containing other transition metals may be mixed and used in a predetermined amount. In addition, as long as the reaction is not adversely affected, a compound other than the transition metal compound, for example, an alkali metal compound, may be added together. Since oxidation-treated carbon is used in mixing with active material particles in the manufacture of electrodes of electrical storage devices, if a compound of an element constituting the active material is added to the carbon raw material, mixing of elements that may become impurities into the active material can be prevented. It is preferable because there is

In step (c), the mixture obtained in step (b) is pulverized to generate a mechanochemical reaction. Examples of the pulverizer for this reaction include a Leica machine, a stone ball grinder, a ball mill, a bead mill, a rod mill, a roller mill, a stirred mill, a planetary mill, a vibration mill, a hybridizer, a mechanochemical compounding device, and a jet mill. there is. The pulverization time depends on the pulverizer to be used, the amount of carbon to be treated, and the like, and is not strictly limited, but is generally in the range of 5 minutes to 3 hours. (d) The step is performed in a non-oxidizing atmosphere such as a nitrogen atmosphere or an argon atmosphere. The heating temperature and heating time are appropriately selected depending on the transition metal compound used. In the subsequent step (e), after removing the transition metal compound and/or its reaction product from the product after heating by means such as dissolving the reaction product with an acid, wash and dry sufficiently, including 10% by mass or more of the total hydrophilic portion Oxidation-treated carbon can be obtained.

In this production method, in the step (c), the transition metal compound acts to accelerate the oxidation of the carbon raw material by a mechanochemical reaction, and the oxidation of the carbon raw material proceeds rapidly. By this oxidation, oxidation-treated carbon containing 10 mass % or more of the whole hydrophilic part is obtained.

The oxidation-treated carbon containing 10% by mass or more of the total hydrophilic moiety is obtained by subjecting the carbon raw material having voids to a strong oxidation treatment, and it is also possible to promote oxidation of the carbon raw material having voids by a method other than the above production method. .

The obtained oxidation-treated carbon is used for the production of electrodes of electrical storage devices such as secondary batteries, electric double-layer capacitors, redox capacitors and hybrid capacitors, Faraday reaction involving electron transfer with ions in the electrolyte of the electrical storage device, or It is used in a mixed form with an electrode active material that expresses a capacity by a non-Faraday reaction that does not involve give-and-take.

(2) electrode

The electrode for a power storage device of the present invention comprises:

(A) a preparation step of preparing an electrode material adhering to the surface of the electrode active material particles by mixing at least a part of the oxidation-treated carbon into a paste by mixing the electrode active material particles and the oxidation-treated carbon, and

(B) a pressing step of forming an active material layer on the current collector with the electrode material and applying a pressure to the active material layer

It is preferably obtained by a manufacturing method comprising

In the step (A), since the oxidation-treated carbon adheres to and covers the surface of the active material particles, aggregation of the active material particles can be suppressed. In addition, due to the pressure exerted on the oxidation-treated carbon during the mixing process, at least a part of the oxidation-treated carbon spreads in a paste-like form so that the surface of the active material particles is partially covered.

(A) As an electrode active material used in a process, the active material used as a positive electrode active material or a negative electrode active material in the conventional electrical storage device can be used without limitation in particular. A single compound may be sufficient as these active materials, and the mixture of 2 or more types of compounds may be sufficient as them.

As an example of the positive electrode active material of the secondary battery, first, layered rock salt type LiMO ₂ , layered Li ₂ MnO ₃ -LiMO ₂ solid solution, and spinel type LiM ₂ O ₄ (wherein M is Mn, Fe, Co, Ni or a combination thereof) meaning) can be included. Specific examples thereof include LiCoO ₂ , LiNiO _{2 ,} LiNi _4/5 Co _1/5 O _{2 , LiNi 1/3} Co _1/3 Mn _1/3 O _{2 , LiNi 1/2 Mn 1/2 O 2 , LiFeO 2 ,} LiMnO ₂ , Li ₂ MnO ₃ -LiCoO ₂ , Li ₂ MnO ₃ -LiNiO ₂ , Li ₂ MnO _{3 -LiNi 1/3} Co _1/3 Mn _1/3 O ₂ , Li ₂ MnO _{3 -LiNi 1/2} Mn _{1 / 2} O ₂ , Li ₂ MnO ₃ -LiNi _1/2 Mn _1/2 O _{2 -LiNi 1/3} Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O _{4 ,} LiMn _{3 / 2} Ni _1/2 O ₄ can be mentioned. In addition, sulfur and sulfides such as Li ₂ S, TiS ₂ , MoS ₂ , FeS ₂ , VS ₂ , Cr _1/2 V _1/2 S ₂ , selenides such as NbSe ₃ , _{VSe 2} , NbSe _{3 , Cr 2 O 5} , Cr ₃ O ₈ , VO ₂ , V ₃ O ₈ , V ₂ O ₅ , V ₆ O ₁₃ In addition to oxides, LiNi _{0 . 8} Co _{0 . 15} Al _{0 . 05} O ₂ , LiVOPO ₄ , LiV ₃ O ₅ , LiV ₃ O ₈ , MoV ₂ O ₈ , Li _{2 FeSiO 4} , Li _{2 MnSiO 4} , LiFePO ₄ , LiFe _1/2 Mn _1/2 PO _{4 , LiMnPO 4} , Li and complex oxides such as ₃ V ₂ (PO ₄ ) ₃ .

Examples of the negative electrode active material of the secondary battery include Fe ₂ O ₃ , MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , CoO, Co ₃ O ₄ , NiO, Ni ₂ O ₃ , TiO, TiO ₂ , SnO, Oxides such as SnO ₂ , SiO ₂ , RuO ₂ , WO, WO ₂ , ZnO, metals such as Sn, Si, Al, Zn, composite oxides such as LiVO ₂ , Li ₃ VO ₄ , Li ₄ Ti ₅ O ₁₂ , Li _{2 . and} nitrides such as ₆ Co _0.4 N, Ge ₃ N ₄ , Zn ₃ N ₂ , and Cu ₃ N .

Examples of the active material in the polarizable electrode of the electric double layer capacitor include carbon materials having a large specific surface area, such as activated carbon, carbon nanofibers, carbon nanotubes, phenol resin carbide, polyvinylidene chloride carbide, and microcrystalline carbon. In the hybrid capacitor, the positive electrode active material exemplified for the secondary battery can be used for the positive electrode, and in this case, the negative electrode is constituted by a polarizable electrode using activated carbon or the like. In addition, the negative electrode active material exemplified for the secondary battery can be used for the negative electrode, and in this case, the positive electrode is constituted by a polarizable electrode using activated carbon or the like. Metal oxides, such as RuO2, MnO2, NiO, can be illustrated as _a positive electrode active material of a redox capacitor, _and a negative electrode is comprised by active material, such as RuO2 _, and polarizable material, such as activated carbon.

Although there is no limitation in the shape and particle diameter of the electrode active material particle mixed with oxidation-treated carbon in the process (A), It is preferable that the average particle diameter of an active material particle is larger than 2 micrometers and 25 micrometers or less. The active material particles having this relatively large average particle diameter themselves improve the electrode density and also promote the formation of paste of the oxidation-treated carbon by its pressing force in the process of mixing with the oxidation-treated carbon. Further, in the step (B) shown below, in the process of applying pressure to the active material layer on the current collector, the active material particles having this relatively large average particle diameter preferably press and oxidize the paste-like oxidized carbon at least in part. The treated carbon is further spread in the form of a paste to densify. As a result, the electrode density increases and the energy density of the electrical storage device is improved.

In addition, it is preferable that the active material particles are composed of fine particles having an average particle diameter of 0.01 to 2 μm, and coarse particles having an average particle diameter of 25 μm or larger than 2 μm that can operate as the same polar active material as the fine particles. . It is said that particles with a small particle size are easy to aggregate, but since the oxidation-treated carbon adheres to and covers the surface of fine particles as well as the surface of coarse particles, aggregation of active material particles can be suppressed, and the active material particles and oxidation-treated carbon The mixing state can be homogenized. Also, as described above, the coarse particles promote paste-formation and densification of the oxidation-treated carbon, increase the electrode density, and improve the energy density of the electrical storage device. Further, in the step (B), in the process of applying pressure to the active material layer on the current collector, while at least a part of the fine particles press the oxidized carbon that has changed to a paste form, coarse particles adjacent to the oxidized carbon spread in a paste form Since it is extruded and filled in the gap|interval formed in between, electrode density further increases, and the energy density of an electrical storage device improves further. It is preferable to select so that it may become the range of 80:20-95:5 by mass ratio, and, as for a coarse particle and a fine particle, it is more preferable that it may select so that it may become the range of 90:10-95:5.

(A) The mass ratio of the electrode active material particles and the oxidized carbon used in the step is preferably in the range of 90:10 to 99.5:0.5 in mass ratio in order to obtain an electrical storage device having a high energy density, and 95:5 to 99 It is more preferable that it is in the range of :1. When the proportion of the oxidation-treated carbon is less than the above range, the conductivity of the active material layer is insufficient, and the coverage of the active material particles by the paste-formed oxidation-treated carbon decreases, and the cycle characteristics tend to decrease. Moreover, when there are more ratios of oxidation-treated carbon than the above-mentioned range, electrode density will fall and there exists a tendency for the energy density of an electrical storage device to fall.

In the step (A), in addition to the electrode active material particles and the oxidation-treated carbon, if necessary, conductive carbon different from the oxidation-treated carbon, a binder, and a solvent for mixing are used to form at least a part of the oxidation-treated carbon into a paste. You may prepare the electrode material which changed and adhered to the surface of the said electrode active material particle.

By use of the solvent, an electrode material in the form of a slurry is obtained.

Examples of other conductive carbon include carbon black such as Ketjen black, acetylene black, furnace black, and channel black, fullerene, carbon nanotube, carbon nanofiber, graphene, amorphous carbon, carbon fiber, which are conventionally used for electrodes of electrical storage devices; Natural graphite, artificial graphite, graphitized Ketjen black, mesoporous carbon, vapor-grown carbon fiber, etc. are used. It is preferable to use the conductive carbon which has electrical conductivity higher than the paste-like conductive carbon derived from oxidation-treated carbon, and use of acetylene black is especially preferable. Since oxidation-treated carbon adheres not only to the surface of active material particle but also to the surface of other conductive carbon, and covers the surface, aggregation of other conductive carbon can be suppressed. Further, in the step (B) shown below, in the process of applying a pressure to the active material layer on the current collector, other conductive carbons are densely filled in the gaps formed by the adjacent particles together with the oxidized carbon spread in the form of paste, Since the electroconductivity of the whole electrode improves, the energy density of an electrical storage device further improves. The range of 3:1-1:3 is preferable by mass ratio, and, as for the ratio of oxidation-treated carbon and other conductive carbon, the range of 2.5:1.5-1.5:2.5 is more preferable. In addition, when other conductive carbon is used, it is preferable that the total amount of the other conductive carbon and the oxidation-treated carbon and the mass ratio of the electrode active material particles are in the range of 10:90 to 0.5:99.5, and in the range of 5:95 to 1:99 more preferably.

As the binder, known binders such as polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl fluoride, and carboxymethyl cellulose are used. It is preferable that content of a binder is 1-30 mass % with respect to the total amount of an electrode material. When it is 1 mass % or less, the intensity|strength of an active material layer is not enough, and when it is 30 mass % or more, the discharge capacity of an electrode falls and problems, such as an internal resistance becoming excessive, arise. As the solvent for mixing, a solvent that does not adversely affect other components in the electrode material, such as N-methylpyrrolidone, can be used without any particular limitation. As long as each component in the mixture is uniformly mixed, the amount of the solvent is not particularly limited. The binder may be used in a form dissolved in a solvent.

(A) There is no limitation in particular in the mixing method of the solvent for the electrode active material particle in a process, oxidation-treated carbon, and conductive carbon different from oxidation-treated carbon used as needed, a binder, and mixing, and mixing.

However, when not using the conductive carbon different from oxidation-treated carbon, it is preferable to dry-mix electrode active material particle and oxidation-treated carbon in (A) process. The electrode material in the form of a slurry can be obtained by sufficiently kneading the obtained product with a binder and a solvent as needed. For dry mixing, a Leica machine, a stone grinder, a ball mill, a beads mill, a rod mill, a roller mill, a stirring mill, a planetary mill, a vibrating mill, a hybridizer, a mechanochemical compounding device, and a jet mill can be used. In particular, when the active material particles and the oxidation-treated carbon are mechanochemically treated, the coating properties of the active material particles by the oxidation-treated carbon and the uniformity of the coating are improved, which is preferable. The time of dry mixing varies depending on the total amount of active material particles and oxidation-treated carbon to be mixed and the mixing device used, but is generally between 1 and 30 minutes. In addition, there is no particular limitation on the kneading method with the binder and the solvent, and may be performed by manual mixing using a mortar, or may be performed using a known mixing apparatus such as a stirrer or a homogenizer. If each component in the electrode material is uniformly mixed, there is no problem even if the mixing time is short.

When the active material particles are composed of fine particles and coarse particles, and other conductive carbon is not used, in the step (A), all of the fine particles, coarse particles, and oxidation-treated carbon may be introduced into a mixing device and dry-mixed. The electrode material in the form of a slurry can be obtained by sufficiently kneading the product obtained by dry mixing together with a binder and a solvent as needed. But,

(A1) dry mixing the oxidation-treated carbon and fine particles to obtain a preliminary mixture, and

(A2) dry mixing the preliminary mixture and coarse particles

It is preferable to carry out dry mixing by dividing into Dry mixing is carried out in steps (A1) and (A2), which is preferable because it is possible to obtain an electrode material in which the coarse and fine particles coated with the oxidation-treated carbon have good dispersibility and are uniformly mixed. In addition, since the product obtained in step (A2) has good familiarity with the binder and solvent, it is possible to easily obtain an electrode material in the form of a slurry in which each component is uniformly mixed. The range of 70:30-90:10 is preferable by mass ratio, and, as for the ratio of the fine particle and oxidation-treated carbon in the step of obtaining a preliminary mixture, the range of 75:25-85:15 is more preferable.

When using conductive carbon different from oxidation-treated carbon, in the (A) process, active material particle|grains, oxidation-treated carbon, and all other conductive carbon may be introduce|transduced into a mixing apparatus, and you may dry-mix. The electrode material in the form of a slurry can be obtained by sufficiently kneading the product obtained by dry mixing together with a binder and a solvent as necessary. But,

(AA1) dry mixing of oxidation-treated carbon and other conductive carbon; and

(AA2) dry mixing the mixture obtained in the step (AA1) and the active material particles

It is preferable to carry out dry mixing by dividing into The mixture obtained in step (AA1) is a "conductive carbon mixture". In this step, the oxidation-treated carbon adheres to the surface of the other conductive carbon, and the oxidation-treated carbon partially progresses into paste-like form, and the oxidized-treated carbon in which at least a part has changed to a paste-like conductive carbon mixture adheres to the surface of the other conductive carbon. this is obtained And, the oxidation-treated carbon, at least a part of which has changed into a paste in step (AA2), also adheres to the surface of the electrode active material particles, so that the active material particles coated with the oxidation-treated carbon and other conductive carbons have good dispersibility and are mixed uniformly electrode material is obtained. In addition, since this conductive carbon mixture has good affinity with the binder and solvent, when obtaining the electrode material in the form of a slurry, instead of kneading with the binder and solvent in step (AA2) and thereafter,

(aa1) wet mixing the conductive carbon mixture, active material particles, binder, and solvent; or

(aa2) wet-mixing a conductive carbon mixture, a binder, and a solvent, and further wet-mixing by adding active material particles; or

(aa3) wet-mixing the conductive carbon mixture, the active material particles, and the solvent, and further wet-mixing by adding a binder;

can also be carried out. Although it is said that fine carbon particles are difficult to be familiar with binders and solvents, by using a conductive carbon mixture, it is possible to easily obtain an electrode material in which each component is uniformly mixed, regardless of the mixing method of this mixture and electrode active material particles. there is. Moreover, when a conductive carbon mixture is prepared beforehand, since mixing of the active material particle and a binder after that can be performed also by either wet or dry method, various production lines can be constructed.

In addition, when the active material particles are composed of fine particles and coarse particles, and other conductive carbon is used, in the step (A), all of the fine particles, coarse particles, oxidation-treated carbon and other conductive carbon are introduced into the mixing device. You may dry-mix. The electrode material in the form of a slurry can be obtained by sufficiently kneading the product obtained by dry mixing together with a binder and a solvent as needed. But,

(AB1) dry mixing of oxidation-treated carbon and other conductive carbon;

(AB2) dry mixing the mixture obtained in step (AB1) with the fine particles, and

(AB3) Dry mixing the mixture obtained in the step (AB2) and the coarse particles

It is preferable to carry out dry mixing by dividing into In addition,

(AC1) dry mixing of oxidation-treated carbon and fine particles;

(AC2) dry mixing the product obtained in the process (AC1) and other conductive carbon, and

(AC3) dry mixing the mixture obtained in the step (AC2) and coarse particles

It is also preferable to carry out dry mixing by dividing into . In these methods, oxidation-treated carbon adheres to the surface of microparticles or other conductive carbons in at least one step of (AB1), (AB2), (AC1), and (AC2), and the oxidation-treated carbon is partially converted into paste. It progresses, and the mixture in which the oxidation-treated carbon, the coarse particle, the micro particle, and other conductive carbon are mixed uniformly with good dispersibility is obtained. In addition, as described above, since the conductive carbon mixture obtained in step (AB1) has good familiarity with the binder and solvent, when obtaining the electrode material in the form of a slurry, step (AB2), step (AB3), and the binder and solvent thereafter Instead of kneading with

(ab1) wet mixing the conductive carbon mixture, the fine particles, the coarse particles, the binder, and the solvent; or

(ab2) wet-mixing the conductive carbon mixture, the binder, and the solvent, and further adding and wet-mixing fine particles and coarse particles; or

(ab3) wet-mixing the conductive carbon mixture, the fine particles, the coarse particles, and the solvent, and further adding a binder and wet-mixing;

can also be carried out. When performing (A) process by these methods, it becomes like the range of 70:30-90:10 by mass ratio, the ratio of the total amount of a microparticle, oxidation-treated carbon, and another conductive carbon, Preferably it is 75:25 The usage-amount of another conductive carbon is selected so that it may become the range of -85:15.

In step (B), an active material layer is formed by applying the electrode material obtained in step (A) on a current collector for constituting a positive electrode or a negative electrode of an electrical storage device, and, if necessary, after drying this active material layer, the active material layer is applied to the active material layer. An electrode is obtained by applying a pressure by a rolling process. (A) After shape|molding the electrode material obtained in the process to a predetermined shape and crimping|bonding it on an electrical power collector, you may perform a rolling process.

In the step (B), when pressure is added to the active material layer, the oxidation-treated carbon, at least partially changed to a paste-like form, further spreads and densifies while covering the surface of the active material particles, so that the active material particles approach each other, and thereby change to a paste-like form While the oxidation-treated carbon covers the surface of the active material particles, it is extruded and densely filled not only in the gaps formed between the adjacent active material particles but also in the pores existing on the surface of the active material particles. Therefore, the amount of active material per unit volume in an electrode increases, and an electrode density increases. In addition, the densely filled paste-like oxidation-treated carbon has sufficient conductivity to function as a conductive agent.

As an electrical power collector for the electrode of an electrical storage device, electrically-conductive materials, such as platinum, gold|metal|money, nickel, aluminum, titanium, steel, and carbon, can be used. As the shape of the current collector, any shape such as a film shape, a foil shape, a plate shape, a net shape, an expanded metal shape, and a cylindrical shape can be adopted. What is necessary is just to dry the active material layer by pressure-reducing and heating as needed to remove a solvent. The pressure applied to the active material layer by the rolling process is generally in the range of 50000 to 1000000 N/cm 2 , and preferably in the range of 100000 to 500000 N/cm 2 . In addition, there is no restriction|limiting in particular in the temperature of a rolling process, You may perform a process at normal temperature, and you may carry out under heating conditions.

In a preferred embodiment of the electrode of the present invention, the paste-like conductive carbon in the active material layer has a width of 50 nm or less and is formed between adjacent electrode active material particles and/or inside the pores existing on the surface of the electrode active material particles. exist. Therefore, the coverage of the surface of the active material particle by paste-form conductive carbon improves, the electroconductivity of the whole active material layer improves, and an electrode density improves. Conductive carbon, such as carbon black, natural graphite, and carbon nanotube, which is used as a conductive agent in the electrode of the conventional electrical storage device, hardly penetrates into the inside of such narrow gap|interval or a hole.

Although the electrode of this invention has the active material layer containing the paste-form conductive carbon with which it filled densely, it turns out that the impregnation in the electrode of the electrolyte solution in an electrical storage device is not suppressed. In the preferred aspect of the electrode of the present invention, when the pore distribution of the active material layer of the electrode is measured by the mercury intrusion method, it is found that the active material layer has pores with a diameter of 5 to 40 nm. These micropores are mainly derived from oxidation-treated carbon and are considered to be pores in the densified paste-like conductive carbon, but it is a sufficient size for the electrolyte solution in the electrical storage device to pass through the paste-like conductive carbon to reach the active material particles. Therefore, the paste-form conductive carbon in an electrode has sufficient electroconductivity and does not suppress the impregnation of the electrolyte solution in an electrical storage device. As a result, the improvement of the energy density of an electrical storage device is brought about.

In addition, in the active material layer of the electrode of the present invention, it is thought that this is because the surface of the active material particles is covered with the oxidized carbon densely spread in a paste form up to the inside of the pores existing on the surface of the active material particles, but in the present invention When a power storage device is constructed using an electrode of In a preferred embodiment of the electrode of the present invention, the dissolved amount of the active material is reduced by about 40% or more compared to the case in which the electrode is formed from the conventional conductive agent such as acetylene black and active material particles. And it originates in the dissolution of an active material being suppressed significantly, and cycling characteristics of an electrical storage device improve significantly.

In particular, oxidation-treated carbon having a hydrophilic portion of 10% by mass or more of the total is compressed integrally when subjected to pressure and easily spreads in a paste form, so that most or all of the surface of the active material particles is placed inside the pores existing on the surface of the active material particles. It is easy to cover up to, and to densify. As a result, 80% or more, preferably 90% or more, particularly preferably 95% or more of the surface of the active material particles in the active material layer of the electrode is derived from oxidation-treated carbon and is in contact with the densified paste-like conductive carbon. is obtained

(3) Power storage device

The electrode of the present invention is used for an electrode of a power storage device such as a secondary battery, an electric double layer capacitor, a redox capacitor, and a hybrid capacitor. A power storage device includes a pair of electrodes (positive electrode, negative electrode) and an electrolyte disposed therebetween as essential elements, but at least one of the positive electrode and the negative electrode is manufactured by the manufacturing method of the present invention.

The electrolyte disposed between the positive electrode and the negative electrode in the electrical storage device may be an electrolyte held in a separator, a solid electrolyte, or a gel electrolyte, and an electrolyte used in a conventional electrical storage device can be used without particular limitation. Hereinafter, representative electrolytes are exemplified. For lithium ion secondary batteries, an electrolyte solution in which lithium salts such as LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ are dissolved in a solvent such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, etc. It is used in the state hold|maintained by separators, such as this polyolefin fiber nonwoven fabric and a glass fiber nonwoven fabric. In addition, Li ₅ La ₃ Nb ₂ O ₁₂ , Li _{1 . 5} Al _{0 . 5} Ti _1.5 (PO ₄ ) ₃ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₇ P ₃ S _{11 and} other inorganic solid electrolytes, lithium salts and polymer compounds such as polyethylene oxide, polymethacrylate, and polyacrylate An organic solid electrolyte composed of a composite of For the electric double layer capacitor and the redox capacitor, an electrolyte solution obtained by dissolving a quaternary ammonium salt such as (C ₂ H ₅ ) ₄ NBF ₄ in a solvent such as acrylonitrile or propylene carbonate is used. For the hybrid capacitor, an electrolyte in which lithium salt is dissolved in propylene carbonate or the like, or an electrolyte in which quaternary ammonium salt is dissolved in propylene carbonate or the like is used.

However, when a solid electrolyte or a gel electrolyte is used as the electrolyte between the positive electrode and the negative electrode, for the purpose of securing an ion conduction path in the active material layer, a solid electrolyte is added to each of the above-mentioned components in the step (A). Prepare the electrode material.

Example

The present invention will be described using the following examples, but the present invention is not limited to the following examples.

(1) Production of oxidation-treated carbon and electrode

Example 1

To 300 mL of 60% nitric acid, 10 g of Ketjen Black (trade name EC300J, manufactured by Ketjen Black International, BET specific surface area of 800 m 2 /g) was added, and the obtained solution was irradiated with ultrasonic waves for 10 minutes, followed by filtration to recover Ketjen Black. The recovered Ketjen Black was washed with water 3 times and dried to obtain acid-treated Ketjen Black. 0.5 g of acid-treated Ketjen Black, 1.98 g of Fe(CH ₃ COO) ₂ , 0.77 g of Li(CH ₃ COO), 1.10 g of C ₆ H ₈ O ₇ .H ₂ O, 1.32 g of CH ₃ COOH, and , H ₃ PO ₄ 1.31 g and 120 mL of distilled water were mixed, and the resulting mixture was stirred with a stirrer for 1 hour, and then evaporated to dryness at 100° C. in the air to collect the mixture. Next, the obtained mixture was introduced into a vibrating ball mill apparatus, and pulverization was performed at 20 hz for 10 minutes. The pulverized powder was heated at 700° C. in nitrogen for 3 minutes to obtain a composite in which LiFePO ₄ was supported on Ketjen Black.

1 g of the obtained composite was added to 100 mL of an aqueous hydrochloric acid solution having a concentration of 30%, and the obtained solution was irradiated with ultrasonic waves for 15 minutes to dissolve LiFePO ₄ in the composite, and the remaining solid was filtered, washed with water, and dried. A part of the dried solid was heated to 900°C in air by TG analysis, and the weight loss was measured. The LiFePO ₄ free oxidation-treated carbon is obtained by repeating the steps of dissolving LiFePO ₄ with an aqueous hydrochloric acid solution, filtration, washing with water, and drying until the weight loss is 100%, that is, it can be confirmed that no LiFePO ₄ remains. got it

Next, 0.1 g of the obtained oxidation-treated carbon was added to 20 mL of an aqueous ammonia solution having a pH of 11, followed by ultrasonic irradiation for 1 minute. The obtained liquid was left to stand for 5 hours to precipitate a solid part. After precipitation of the solid part, the residual part from which the supernatant liquid was removed was dried, and the weight of the solid after drying was measured. The weight ratio of the weight obtained by subtracting the weight of the dried solid from the weight of 0.1 g of the first oxidation-treated carbon to the weight of 0.1 g of the first oxidation-treated carbon was defined as the content of the "hydrophilic part" in the oxidation-treated carbon.

Fe(CH ₃ COO) ₂ , Li(CH ₃ COO), C ₆ H ₈ O ₇ ·H ₂ O, CH ₃ COOH, and H ₃ PO ₄ A mixture obtained by introducing distilled water into distilled water was 1 After stirring for an hour, it was evaporated to dryness at 100°C in air, and then heated at 700°C in nitrogen for 3 minutes to obtain fine particles of LiFePO ₄ having a primary particle size of 100 nm (average particle size of 100 nm). Next, commercially available coarse particles of LiFePO ₄ (primary particle diameter of 0.5 to 1 μm, secondary particle diameter of 2 to 3 μm, average particle diameter of 2.5 μm), the obtained fine particles, and the oxidation-treated carbon were mixed with 90:9:1 The electrode material is obtained by mixing in a mass ratio of After drying, a rolling treatment was performed to obtain an electrode. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this electrode.

Example 2

In the procedure in Example 1, 0.5 g of acid-treated Ketjen Black, 1.98 g of Fe(CH ₃ COO) ₂ , 0.77 g of Li(CH ₃ COO), and 1.10 g of C ₆ H ₈ O ₇ ·H ₂ O And, CH ₃ COOH 1.32 g, H ₃ PO ₄ 1.31 g, and a portion for mixing 120 mL of distilled water, acid-treated Ketjen Black 1.8 g, Fe(CH ₃ COO) ₂ 0.5 g, Li(CH ₃ COO) 0.19 g, C ₆ H ₈ O ₇ ·H ₂ O 0.28 g, CH ₃ COOH 0.33 g, H ₃ PO ₄ 0.33 g, and 250 mL of distilled water Except for changing the order of mixing, Example 1 sequence was repeated.

Example 3

After adding 10 g of Ketjen Black used in Example 1 to 300 mL of 40% nitric acid, and irradiating ultrasonic waves for 10 minutes to the obtained liquid, it filtered and collect|recovered Ketjen Black. The recovered Ketjen Black was washed with water 3 times and dried to obtain acid-treated Ketjen Black. The procedure of Example 2 was repeated except that 1.8 g of this acid-treated Ketjen Black was used instead of 1.8 g of the acid-treated Ketjen Black used in Example 2.

Comparative Example 1

After adding 10 g of Ketjen Black used in Example 1 to 300 mL of 60% nitric acid, and irradiating an ultrasonic wave to the obtained liquid for 1 hour, it filtered and collect|recovered Ketjen Black. The recovered Ketjen Black was washed with water 3 times and dried to obtain acid-treated Ketjen Black. This acid-treated Ketjen Black was heated at 700° C. in nitrogen for 3 minutes. About the obtained oxidation-treated carbon, content of the hydrophilic part was measured in the same procedure as the procedure in Example 1. Moreover, using the obtained oxidation-treated carbon, the LiFePO ₄ containing electrode was created in the same procedure as the procedure in Example 1, and the electrode density was computed.

Comparative Example 2

After adding 10 g of Ketjen Black used in Example 1 to 300 mL of 30% nitric acid, and irradiating an ultrasonic wave to the obtained liquid for 10 minutes, it filtered and collect|recovered Ketjen Black. The recovered Ketjen Black was washed with water 3 times and dried to obtain acid-treated Ketjen Black. Then, it heated at 700 degreeC for 3 minutes in nitrogen without performing grinding|pulverization by a vibrating ball mill. About the obtained oxidation-treated carbon, content of the hydrophilic part was measured in the same procedure as the procedure in Example 1. Moreover, using the obtained oxidation-treated carbon, the LiFePO ₄ containing electrode was created in the same procedure as the procedure in Example 1, and the electrode density was computed.

Comparative Example 3

In order to confirm the contribution of the hydrophilic portion to the electrode density, 40 mg of the oxidation-treated carbon obtained in Example 1 was added to 40 mL of pure water, sonicated for 30 minutes to disperse the carbon in the pure water, and the dispersion was left for 30 minutes. A solid was obtained by removing the supernatant and drying the remaining portion. About this solid, content of the hydrophilic part was measured in the same procedure as the procedure in Example 1. Moreover, the LiFePO ₄ containing electrode was created in the same procedure as the procedure in Example 1 using the obtained solid, and the electrode density was computed.

Comparative Example 4

About the Ketjen black raw material used in Example 1, content of the hydrophilic part was measured in the same procedure as the procedure in Example 1. Moreover, using this Ketjen Black raw material, the LiFePO ₄ containing electrode was created in the same procedure as the procedure in Example 1, and the electrode density was computed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the relationship between the hydrophilic part content with respect to the carbon of Examples 1-3 and Comparative Examples 1-4, and the electrode density with respect to the electrode of Examples 1-3 and Comparative Examples 1-4. As is clear from Fig. 1, when the content of the hydrophilic portion exceeds 8% by mass of the total oxidation-treated carbon, the electrode density starts to increase, and when it exceeds 9% by mass, the electrode density begins to increase rapidly, and the It turned out that the high electrode density of 2.6 g/cc or more is obtained when content exceeds 10 mass % of the whole oxidation-treated carbon. Further, as is clear from the comparison of the results of Example 1 with the results of Comparative Example 3, it was found that the contribution of the hydrophilic portion of the oxidation-treated carbon to the improvement of the electrode density was large. And, as a result of observation by the SEM photograph, it was confirmed that when the content of the hydrophilic portion of the oxidation-treated carbon increased and the electrode density started to increase rapidly, the oxidation-treated carbon became paste-like rapidly.

(2) Evaluation as a lithium ion secondary battery

(i) Active material: LiNi _{0 . 5} Mn _{0 . 3} Co _{0 . 2} O ₂

Example 4

Li ₂ CO ₃ , Ni(CH ₃ COO) ₂ , Mn(CH ₃ COO) ₂ , and Co(CH ₃ COO) ₂ were introduced into distilled water, and the resulting mixture was stirred with a stirrer for 1 hour, and then air After evaporation to dryness at 100°C, mixing with a ball mill and heating at 800°C in air for 10 minutes to obtain LiNi _0.5 Mn _0.3 Co _0.2 O ₂ microparticles having an average particle size of 0.5 µm. These fine particles and the oxidation-treated carbon obtained in Example 1 were mixed in a mass ratio of 90:10 to obtain a preliminary mixture. Next, 86 parts by mass of commercially available LiNi _{0 . 5} Mn _{0 . 3} Co _{0 .} Coarse particles of ₂ O ₂ (average particle diameter of 5 µm), 9 parts by mass of the above preliminary mixture, and 2 parts by mass of acetylene black (primary particle diameter of 40 nm) are mixed, and 3 parts by mass of polyvinylidene fluoride and an appropriate amount N-methylpyrrolidone was added, kneaded sufficiently to form a slurry, and the slurry was applied on an aluminum foil and dried, followed by rolling to obtain a positive electrode for a lithium ion secondary battery. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 4.00 g/cc. Moreover, using the obtained positive electrode, the ethylene carbonate/diethyl carbonate 1: ₁ solution of 1M LiPF6 was used as electrolyte solution, and the lithium ion secondary battery which used lithium as the counter electrode was created. About the obtained battery, the charging/discharging characteristic was evaluated under the conditions of a wide range of current densities.

Example 5

94 parts by mass of commercially available LiNi _{0 . 5} Mn _{0 . 3} Co _{0 . 2} O ₂ particles (average particle size: 5 µm), 2 parts by mass of the oxidation-treated carbon obtained in Example 1, and 2 parts by mass of acetylene black (primary particle diameter of 40 nm) are mixed, and further 2 parts by mass of polyvinyl fluoride Leadene and an appropriate amount of N-methylpyrrolidone were added, kneaded sufficiently to form a slurry, and the slurry was coated on an aluminum foil and dried, followed by rolling to obtain a positive electrode for a lithium ion secondary battery. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 3.81 g/cc. Moreover, using the obtained positive electrode, the ethylene carbonate/diethyl carbonate 1: ₁ solution of 1M LiPF6 was used as electrolyte solution, and the lithium ion secondary battery which used lithium as the counter electrode was created. About the obtained battery, the charging/discharging characteristic was evaluated under the conditions of a wide range of current densities.

Comparative Example 5

94 parts by mass of commercially available LiNi _{0 . 5} Mn _{0 . 3} Co _{0 . 2} O ₂ particles (average particle diameter of 5 µm) and 4 parts by mass of acetylene black (primary particle diameter of 40 nm) are mixed, and 2 parts by mass of polyvinylidene fluoride and an appropriate amount of N-methylpyrrolidone are added After kneading and forming a slurry, this slurry was apply|coated on aluminum foil and dried, the rolling process was performed and the positive electrode for lithium ion secondary batteries was obtained. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 3.40 g/cc. Moreover, using the obtained positive electrode, the ethylene carbonate/diethyl carbonate 1: ₁ solution of 1M LiPF6 was used as electrolyte solution, and the lithium ion secondary battery which used lithium as the counter electrode was created. About the obtained battery, the charging/discharging characteristic was evaluated under the conditions of a wide range of current densities.

FIG. 2 shows an SEM photograph of a cross section of the positive electrode of the lithium ion secondary battery of Example 5, and FIG. 3 shows a SEM photograph of a cross section of the positive electrode of the lithium ion secondary battery of Comparative Example 5. In each figure, (A) is a photograph of 1500 magnification, (B) is a photograph of 25000 magnification. Although the thickness of the active material layer is indicated by t in FIGS. 2A and 3A , the lithium ion 2 of Example 5 is the same as the content of the active material particles and carbon in the active material layer. It turns out that the active material layer in a secondary battery is thinner than the active material layer in the lithium ion secondary battery of Comparative Example 5. In addition, from the comparison of Fig. 2 (A) and Fig. 3 (A), in the active material layer in the lithium ion secondary battery of Example 5, the active material particles approached each other, and the area of the entire active material layer in the image was It can be seen that the ratio of the area occupied by carbon to the carbon is small. Moreover, as can be grasped|ascertained from FIG.2(B) and FIG.3(B), the form of carbon in both is remarkably different. In the active material layer (FIG. 3(B)) of the lithium ion secondary battery of Comparative Example 5, the grain boundaries of the primary carbon (acetylene black) particles are clear, and in addition to the voids between the carbon particles, the active material particles and the carbon particles While large voids exist in the vicinity of the interface, particularly in the vicinity of pores formed on the surface of the active material particles, in the active material layer (FIG. 2B) in the lithium ion secondary battery of Example 5, the carbon primary particles It was found that no grain boundaries were observed, and the carbon was paste-like, and the paste-like carbon penetrated deep into the pores (gaps between primary particles) having a width of 50 nm or less of the active material particles, so there were almost no voids. can Moreover, it turns out that 90% or more of the surfaces of the active material particles are in contact with paste-like carbon. It turned out that the difference in the electrode density in the positive electrode of the lithium ion secondary battery of Example 5 and Comparative Example 5 was caused by the difference in the form of this carbon.

As described above, since the active material layer in Example 5 is thinner than the active material layer in Comparative Example 5, it can be seen that the material filling rate in the active material layer of Example 5 is large, but the following formula is used Thus, the material filling rate was confirmed. In addition, a theoretical electrode density is an electrode density when it is assumed that the space|gap in an active material layer is 0 %.

Material filling factor (%) = electrode density × 100/theoretical electrode density (I)

Theoretical electrode density (g/cc)

= 100/{a/X+b/Y+ (100-a-b)/Z} (II)

a: mass % of active material with respect to the entire active material layer

b: mass % of carbon with respect to the entire active material layer

100-a-b: mass % of polyvinylidene fluoride with respect to the entire active material layer

X: True density of active material Y: True density of carbon black

Z: true density of polyvinylidene fluoride

As a result, the material filling rate of the active material layer in Example 5 was 86.8%, and the material filling rate of the active material layer in Comparative Example 5 was 79.1%, in an electrode containing paste-like conductive carbon derived from oxidation-treated carbon. An improvement of 7.7% or more of the filling rate was confirmed.

About the active material layer in Example 5 and the active material layer in Comparative Example 5 in FIG. 4, the result of having measured the pore distribution by the mercury intrusion method is shown. It turns out that the active material layer in Comparative Example 5 hardly had pores with a diameter of less than 20 nm, and most of the pores were pores showing peaks at about 30 nm in diameter, about 40 nm in diameter, and about 150 nm in diameter. The pores exhibiting a peak at about 150 nm in diameter are mainly due to the active material particles, and the pores showing peaks at about 30 nm in diameter and about 40 nm in diameter are considered to be pores mainly found between particles of acetylene black. On the other hand, in the active material layer in Example 5, the number of pores with a diameter of about 100 nm or more among the pores of the active material layer in Comparative Example 5 is decreasing, and instead of this, pores in the range of 5 to 40 nm in diameter are increasing. it can be seen that It is thought that the pore of diameter about 100 nm or more is decreasing because the pore of an active material particle is covered with paste-form conductive carbon. In addition, the pores having a diameter of 5 to 40 nm are mainly derived from oxidation-treated carbon and are considered to be pores in the densified paste-like conductive carbon, but the size sufficient for the electrolyte solution in the electrical storage device to pass through the paste-like conductive carbon to reach the active material particles. am. Therefore, it was judged that the paste-form conductive carbon in an electrode did not suppress the impregnation of the electrolyte solution in an electrical storage device.

5 is a diagram showing the relationship between the rate and the discharge capacity per volume of the positive electrode active material layer for the lithium ion secondary batteries of Examples 4, 5, and Comparative Example 5; The lithium ion secondary battery of Example 5 exhibits an increased capacity than the lithium ion secondary battery of Comparative Example 5, and the lithium ion secondary battery of Example 4 has a further increased capacity than the lithium ion secondary battery of Example 5 showed That is, as the electrode density of the positive electrode increased, the discharge capacity per volume also increased. In addition, these secondary batteries exhibited approximately the same rate characteristics. Also from this, the paste-like conductive carbon derived from the oxidation-treated carbon contained in the active material layer in the secondary batteries of Examples 4 and 5 and densified has sufficient conductivity to function as a conductive agent, and the secondary battery It turns out that the impregnation of the electrolyte solution in a battery is not suppressed. Although the positive electrode of the secondary battery of Example 4 and the positive electrode of the secondary battery of Example 5 have approximately the same content of active material particles and carbon in the active material layer, the former exhibits a higher electrode density than the latter, but this In the active material layer in the positive electrode of the secondary battery of Example 4, fine particles are extruded into the gap formed between adjacent coarse particles together with the paste-formed oxidation treated carbon while pressing the oxidation treated carbon obtained in Example 1 It was thought to be due to charging.

For the lithium ion secondary batteries of Example 5 and Comparative Example 5, charging and discharging were repeated in the range of 4.6 to 3.0 V under conditions of 60° C. and a charge/discharge rate of 0.5 C. 6 shows the results of the obtained cycle characteristics. It can be seen that the secondary battery of Example 5 has superior cycle characteristics than the secondary battery of Comparative Example 5. As can be seen from the comparison between FIG. 2 and FIG. 3, approximately the entire surface of the active material particles in the active material layer in the former is covered with dense paste-like carbon up to the depth of the pores on the surface of the active material particles, and this It was thought that it was because the dense paste-like carbon suppressed deterioration of an active material.

(ii) active material: LiCoO ₂

Example 6

Li ₂ CO ₃ , Co(CH ₃ COO) ₂ , and C ₆ H ₈ 0 ₇ ·H ₂ O were introduced into distilled water, and the resulting mixture was stirred with a stirrer for 1 hour, and then evaporated to dryness at 100° C. in air. After heating, LiCoO ₂ microparticles having an average particle diameter of 0.5 µm were obtained by heating at 800°C in air for 10 minutes. These fine particles and the oxidation-treated carbon obtained in Example 1 were mixed in a mass ratio of 90:10 to obtain a preliminary mixture. Next, 86 parts by mass of commercially available coarse particles of LiCoO ₂ (average particle size of 10 µm), 9 parts by mass of the above preliminary mixture, and 2 parts by mass of acetylene black (primary particle diameter of 40 nm) are mixed, and 3 parts by mass of poly After adding vinylidene fluoride and an appropriate amount of N-methylpyrrolidone and kneading it sufficiently to form a slurry, this slurry was coated on an aluminum foil and dried, followed by rolling to obtain a positive electrode for a lithium ion secondary battery. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 4.25 g/cc. Moreover, using the obtained positive electrode, the ethylene carbonate/diethyl carbonate 1: ₁ solution of 1M LiPF6 was used as electrolyte solution, and the lithium ion secondary battery which used lithium as the counter electrode was created. About the obtained battery, the charging/discharging characteristic was evaluated under the conditions of a wide range of current densities.

Example 7

94 parts by mass of commercially available LiCoO ₂ particles (average particle size of 10 µm), 2 parts by mass of the oxidation-treated carbon obtained in Example 1, and 2 parts by mass of acetylene black (primary particle diameter of 40 nm) are mixed, and further 2 parts by mass Negative polyvinylidene fluoride and an appropriate amount of N-methylpyrrolidone are added and thoroughly kneaded to form a slurry, the slurry is coated on an aluminum foil and dried, and then a rolling treatment is performed to obtain a positive electrode for a lithium ion secondary battery. got it The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 4.05 g/cc. Moreover, using the obtained positive electrode, the ethylene carbonate/diethyl carbonate 1: ₁ solution of 1M LiPF6 was used as electrolyte solution, and the lithium ion secondary battery which used lithium as the counter electrode was created. About the obtained battery, the charging/discharging characteristic was evaluated under the conditions of a wide range of current densities.

Comparative Example 6

94 parts by mass of commercially available LiCoO ₂ particles (average particle size of 10 µm) and 4 parts by mass of acetylene black (primary particle diameter of 40 nm) are mixed, and 2 parts by mass of polyvinylidene fluoride and an appropriate amount of N-methylpyrrolidone was added, kneaded sufficiently to form a slurry, and the slurry was applied on an aluminum foil and dried, followed by rolling to obtain a positive electrode for a lithium ion secondary battery. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 3.60 g/cc. Moreover, using the obtained positive electrode, the ethylene carbonate/diethyl carbonate 1: ₁ solution of 1M LiPF6 was used as electrolyte solution, and the lithium ion secondary battery which used lithium as the counter electrode was created. About the obtained battery, the charging/discharging characteristic was evaluated under the conditions of a wide range of current densities.

The material filling rate was confirmed using Formula (I) and (II) mentioned above about the active material layer in Example 7 and the active material layer in Comparative Example 6. As a result, the material filling rate of the active material layer in Example 7 was 85.6%, and the material filling rate of the active material layer in Comparative Example 6 was 79.1%, in an electrode containing paste-like conductive carbon derived from oxidation-treated carbon. An improvement of 6.5% or more of the filling rate was confirmed.

7 is a view showing the relationship between the rate and the discharge capacity per volume of the positive electrode active material layer for the lithium ion secondary batteries of Examples 6, 7, and Comparative Example 6; It turns out that similarly to the result shown in FIG. 5, the discharge capacity also increases as electrode density increases, and substantially the same rate characteristic is obtained. Charging/discharging was repeated in the range of 4.3-3.0V under the conditions of 60 degreeC and the charge-discharge rate of 0.5C about the lithium ion secondary battery of Example 7 and Comparative Example 6. Fig. 8 shows the results of the obtained cycle characteristics. 6 , it can be seen that the secondary battery of Example 7 has superior cycle characteristics than the secondary battery of Comparative Example 6.

(iii) Active material: Li _{1 . 2} Mn _{0 . 56} Ni _{0 . 17} Co _{0 . 07} O ₂

Example 8

1.66 g of Li(CH ₃ COO), 2.75 g of Mn(CH ₃ COO) ₂ .4H ₂ O, and 0.85 g of Ni(CH ₃ COO) ₂ .4H ₂ O, and Co(CH ₃ COO) ₂ .4H ₂ 0.35 g of O and 200 mL of distilled water were mixed, the solvent was removed using an evaporator, and the mixture was collected. Next, the collected mixture was introduced into a vibrating ball mill, and pulverized at 15 hz for 10 minutes to obtain a uniform mixture. The mixture after pulverization is heated in air at 900°C for 1 hour, and lithium excess solid solution Li ₁ having an average particle size of 1 µm or less _{. 2} Mn _{0 . 56} Ni _{0 . 17} Co _{0 . 07} O ₂ crystals were obtained. 91 parts by mass of the crystal grains and 4 parts by mass of the oxidation-treated carbon obtained in Example 1 are mixed, and further, 5 parts by mass of polyvinylidene fluoride and an appropriate amount of N-methylpyrrolidone are added and sufficiently kneaded to form a slurry After forming and apply|coating this slurry on aluminum foil and drying, the rolling process was performed and the positive electrode for lithium ion secondary batteries was obtained. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 3.15 g/cc. Furthermore, using the obtained positive electrode, the lithium ion secondary battery which used 1 M LiPF6 ethylene carbonate/diethyl carbonate 1:1 solution as electrolyte solution, and used lithium as the counter electrode was created. About the obtained battery, the charging/discharging characteristic was evaluated under the conditions of a wide range of current densities.

Comparative Example 7

Li ₁ obtained in Example 8 of 91 parts by mass _{. 2} Mn _{0 . 56} Ni _{0 . 17} Co _{0 . 07} O ₂ particles and 4 parts by mass of acetylene black (primary particle diameter of 40 nm) were mixed, and 5 parts by mass of polyvinylidene fluoride and an appropriate amount of N-methylpyrrolidone were added and sufficiently kneaded to form a slurry, , After apply|coating this slurry on aluminum foil and drying it, the rolling process was performed and the positive electrode for lithium ion secondary batteries was obtained. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 2.95 g/cc. Moreover, using the obtained positive electrode, the ethylene carbonate/diethyl carbonate 1: ₁ solution of 1M LiPF6 was used as electrolyte solution, and the lithium ion secondary battery which used lithium as the counter electrode was created. About the obtained battery, the charging/discharging characteristic was evaluated under the conditions of a wide range of current densities.

9 is a diagram showing the relationship between the rate and the discharge capacity per volume of the positive electrode active material layer for the lithium ion secondary batteries of Example 8 and Comparative Example 7. FIG. It turns out that similarly to the result shown in FIG. 5, the discharge capacity also increases as electrode density increases, and substantially the same rate characteristic is obtained. For the lithium ion secondary batteries of Example 8 and Comparative Example 7, charging and discharging were repeated in the range of 4.8-2.5V under the conditions of 25 degreeC and the charge-discharge rate of 0.5C. In Fig. 10, the results of the obtained cycle characteristics are shown. 6 , it can be seen that the secondary battery of Example 8 has superior cycle characteristics than the secondary battery of Comparative Example 7.

(iv) modification of oxidation-treated carbon

Example 9

To 300 mL of 60% nitric acid, 10 g of voided furnace black (average particle size of 20 nm, BET specific surface area of 1400 m 2 /g) was added, and the resulting solution was irradiated with ultrasonic waves for 10 minutes, followed by filtration to recover furnace black. The recovered furnace black was washed with water 3 times and dried to obtain an acid-treated furnace black. 0.5 g of this acid-treated furnace black, 1.98 g of Fe(CH ₃ COO) ₂ , 0.77 g of Li(CH ₃ COO), 1.10 g of C ₆ H ₈ O ₇ .H ₂ O, 1.32 g of CH ₃ COOH , H ₃ PO ₄ 1.31 g and 120 mL of distilled water were mixed, and the resulting mixture was stirred with a stirrer for 1 hour, and then evaporated to dryness at 100° C. in the air to collect the mixture. Next, the obtained mixture was introduced into a vibrating ball mill apparatus, and pulverization was performed at 20 hz for 10 minutes. The powder after pulverization was heated at 700° C. in nitrogen for 3 minutes to obtain a composite in which LiFePO ₄ was supported on furnace black.

1 g of the obtained composite was added to 100 mL of a 30% hydrochloric acid solution, and the obtained solution was irradiated with ultrasonic waves for 15 minutes to dissolve LiFePO ₄ in the composite, and the remaining solid was filtered, washed with water, and dried. A part of the dried solid was heated to 900°C in air by TG analysis, and the weight loss was measured. The LiFePO ₄ free oxidation-treated carbon is obtained by repeating the steps of dissolving LiFePO ₄ with an aqueous hydrochloric acid solution, filtration, washing with water, and drying until the weight loss is 100%, that is, it can be confirmed that no LiFePO ₄ remains. got it

Next, 0.1 g of the obtained oxidation-treated carbon was added to 20 mL of an aqueous ammonia solution having a pH of 11, followed by ultrasonic irradiation for 1 minute. The obtained liquid was left to stand for 5 hours to precipitate a solid part. After precipitation of the solid part, the residual part from which the supernatant liquid was removed was dried, and the weight of the solid after drying was measured. The weight ratio of the weight obtained by subtracting the weight of the dried solid from the weight of 0.1 g of the first oxidation-treated carbon to the weight of 0.1 g of the first oxidation-treated carbon was defined as the content of the "hydrophilic part" in the oxidation-treated carbon. This oxidation-treated carbon contained 13% hydrophilic portion. In addition, the hydrophilic portion in the furnace black having voids used as a raw material is only 2%.

94 parts by mass of commercially available LiNi _{0 . 5} Mn _{0 . 3} Co _{0 . 2} O ₂ particle|grains (average particle diameter of 5 micrometers), 2 mass parts of obtained oxidation-treated carbon, and 2 mass parts of acetylene black (primary particle diameter of 40 nm) were mixed. In Fig. 11, a SEM photograph of 50000 times of the obtained mixture is shown. Although the surface of the particles is partially covered with a paste-like substance and the outline is not clearly grasped, this paste-like substance spreads while oxidation-treated carbon obtained by oxidizing the furnace black raw material covers the particle surface under the pressure of mixing. . Moreover, it turns out that acetylene black with a primary particle diameter of 40 nm is disperse|distributing favorably. Although it is generally said that fine particles are easy to agglomerate, the aggregation of fine particles is effectively suppressed by oxidation-treated carbon.

Next, 2 parts by mass of polyvinylidene fluoride and an appropriate amount of N-methylpyrrolidone are added to the resulting mixture, thoroughly kneaded to form a slurry, and the slurry is coated on an aluminum foil and dried, followed by rolling treatment for lithium A positive electrode for an ion secondary battery was obtained. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 3.80 g/cc. Moreover, using the obtained positive electrode, the ethylene carbonate/diethyl carbonate 1: ₁ solution of 1M LiPF6 was used as electrolyte solution, and the lithium ion secondary battery which used lithium as the counter electrode was created. About the obtained battery, the charging/discharging characteristic was evaluated under the conditions of a wide range of current densities. Moreover, charging and discharging were repeated about the obtained battery in the range of 4.6-3.0V under the conditions of 60 degreeC and the charging/discharging rate of 0.5C.

Example 9 and Comparative Example 5 were different in the type of carbon for the positive electrode, but other conditions were the same. In Example 9, oxidation-treated carbon and acetylene black obtained from voided furnace black raw materials were used, but in Comparative Example 5, Only acetylene black was used. The electrode density of the positive electrode in Comparative Example 5 was 3.40 g/cc, and the electrode density was significantly improved by the use of oxidation-treated carbon. Incidentally, Examples 9 and 5 differ in the type of oxidation-treated carbon for the positive electrode, but other conditions are the same. In Example 5, oxidation-treated carbon obtained from a Ketjen black raw material was used, but in Example 9, furnace black Oxidized carbon obtained from the raw material was used. The electrode density of the positive electrode in Example 5 was 3.81 g/cc, and substantially the same electrode density was obtained irrespective of the difference of the raw material in oxidation-treated carbon.

12 shows the relationship between the rate and the discharge capacity per volume of the positive electrode active material layer for the lithium ion secondary batteries of Example 9 and Comparative Example 5, and FIG. 13 shows the lithium ion secondary batteries of Example 9 and Comparative Example 5 Shows the results of cycle characteristics for It can be seen from Fig. 12 that, as the electrode density increases, the discharge capacity also increases, and substantially the same rate characteristics are obtained. In addition, when the rate characteristics of the secondary battery of Example 5 in FIG. 5 are compared with the rate characteristics of the secondary battery of Example 9 in FIG. 12, differences in raw materials in the oxidation-treated carbon used for the positive electrode It can be seen that almost the same rate characteristics are obtained regardless of . 13 , it can be seen that the secondary battery of Example 9 has superior cycle characteristics than the secondary battery of Comparative Example 5. Further, when the cycle characteristics of the secondary battery of Example 5 in FIG. 6 and the cycle characteristics of the secondary battery of Example 9 in FIG. 13 are compared, differences in raw materials in the oxidation-treated carbon used for the positive electrode It can be seen that almost the same cycle characteristics are obtained regardless of the

(3) solubility of active material

As described above, in the lithium ion secondary battery provided with the electrode of the present invention, excellent cycle characteristics are obtained because substantially the entire surface of the active material particles is coated with paste-like carbon, and this paste-like carbon causes deterioration of the active material. Although it is thought that this is because it suppresses this, in order to confirm this, the solubility of the active material was investigated.

Each of the oxidation-treated carbon and acetylene black obtained in Example 1 were LiFePO ₄ particles having an average particle diameter of 0.22 μm, LiCoO ₂ particles having an average particle diameter of 0.26 μm, and LiNi ₀ having an average particle diameter of 0.32 μm _{. 5} Mn _{0 . 3} Co _{0 .} Mix with ₂ O ₂ particles in a mass ratio of 5:95, and add 5% by mass of polyvinylidene fluoride and an appropriate amount of N-methylpyrrolidone of the total, sufficiently knead to form a slurry, and apply on aluminum foil and dried and subjected to a rolling treatment to obtain an electrode. A coin-type battery was created using this electrode and the electrolyte obtained by adding 1000 ppm of water to a 1:1 solution of 1 M LiPF ₆ in ethylene carbonate/diethyl carbonate. In this test, microparticles with a large specific surface area were used in order to increase the area of the active material in contact with the electrolyte. In addition, 1000 ppm of water was added for the purpose of an accelerated test, since the active material is easy to melt|dissolve so that there is much water. After leaving this battery at 60 DEG C for one week, it was disassembled, the electrolyte was collected, and the amount of metal dissolved in the electrolyte was analyzed by an ICP emission spectrometer. The results obtained in Table 1 are shown.

As is clear from Table 1, the paste-like conductive carbon derived from the oxidation-treated carbon obtained in Example 1 significantly suppresses the dissolution of the active material in the electrolyte as compared with acetylene black. This is thought to be because the oxidation-treated carbon obtained in Example 1 effectively suppresses aggregation of the microparticles even if the active material is microparticles having an average particle diameter of 0.22 to 0.32 μm, and covers approximately the entire surface of the active material particles. do.

(4) Mixed state of oxidation-treated carbon and active material

In order to confirm the mixed state of an active material and carbon, the following experiment was performed.

(i) Mixing of fine particles and carbon

LiNi ₀ of each of the oxidation-treated carbon and acetylene black obtained in Example 1 with an average particle diameter of 0.32 micrometer _{. 5} Mn _{0 . 3} Co _{0 .} It introduce|transduced into the mortar at the mass ratio of ₂ O2 microparticles|fine _- particles and 20:80, and performed dry mixing. 14 shows an SEM photograph at a magnification of 50000 times. When acetylene black is used as carbon, it turns out that microparticles|fine-particles are aggregated in spite of the same mixing conditions compared with the case where the oxidation-treated carbon obtained in Example 1 is used. Therefore, it turns out that the oxidation-treated carbon obtained in Example 1 effectively suppresses aggregation of microparticles|fine-particles.

(ii) a mixture of coarse particles and carbon

LiNi ₀ of each of the oxidation-treated carbon and acetylene black obtained in Example 1 with an average particle diameter of 5 micrometers _{. 5} Mn _{0 . 3} Co _{0 .} It was introduced into a mortar at a mass ratio of ₂ O ₂ coarse particles and 4:96, followed by dry mixing. 15 shows an SEM photograph at a magnification of 100000 times. When acetylene black is used as the carbon, coarse particles and acetylene black are present separately. However, when the oxidation-treated carbon obtained in Example 1 is used, the coarse particles are covered with a paste-like substance so that the outline of the coarse particles is clear. It can be seen that it is not understood. This paste-like substance spreads while the oxidation-treated carbon obtained in Example 1 covered the surface of the coarse particle by the pressure of mixing. By the rolling treatment at the time of electrode creation, the oxidation-treated carbon obtained in Example 1 spreads further into a paste-like shape and densifies while covering the surface of the active material particles, so that the active material particles approach each other, and thereby the paste-formed oxidation-treated carbon is produced It is thought that the electrode density increased because the amount of active material per unit volume in the electrode increased because it was densely filled by extruding into the gap formed between adjacent active material particles while covering the surface of the active material particles.

(5) Use of conductive carbon mixture

(i) Active material: LiNi _{0 . 5} Mn _{0 . 3} Co _{0 . 2} O ₂

Example 10

The oxidation-treated carbon obtained in Example 1 and acetylene black (primary particle diameter of 40 nm) were introduced into a ball mill at a mass ratio of 1:1, followed by dry mixing to obtain a conductive carbon mixture. The SEM photograph of the obtained conductive carbon mixture is shown in FIG. 16, and the TEM photograph is shown in FIG. 17, respectively. FIG. 16 is a magnification of 50000, (A) of FIG. 17 is a magnification of 100000, and (B) of FIG. 17 is a magnification of 500,000. In the SEM photograph of FIG. 16 , it can be seen that paste-like carbon is present on the surface because the outline of the carbon particles is not clearly grasped. Moreover, from the TEM photograph of FIG. 17, it turns out that the conductive carbon mixture is comprised with a granular material and the layered material on the surface of a granular material. The broken line in Fig. 17B indicates the surface of the granular material. The granular material is an acetylene black particle, and the layered material is a layer formed by collapsing oxidation-treated carbon and adhering to the surface of the acetylene black particle. From FIG. 17B, it can be seen that the layered material is composed of a paste-like part to which non-particulate amorphous carbon is connected, and a fibrous or needle-like part.

Next, 4 parts by mass of the obtained conductive carbon mixture, 2 parts by mass of polyvinylidene fluoride, and an appropriate amount of N-methylpyrrolidone are wet-mixed, and further 94 parts by mass of commercially available LiNi _0.5 Mn _0.3 Co _0.2 O ₂ particles ( average particle diameter of 5 µm) was added and wet-mixed to form a slurry. After apply|coating this slurry on aluminum foil and drying it, the rolling process was performed and the positive electrode for lithium ion secondary batteries was obtained. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 3.81 g/cc. Moreover, using the obtained positive electrode, the ethylene carbonate/diethyl carbonate 1: ₁ solution of 1M LiPF6 was used as electrolyte solution, and the lithium ion secondary battery which used lithium as the counter electrode was created. About the obtained battery, the discharge curve was measured in the range of 4.5-3.0V under the conditions of 25 degreeC and the discharge rate of 0.5C, and direct current internal resistance (DCIR) was computed from the voltage drop.

Example 11

4 parts by mass of the conductive carbon mixture obtained in Example 10, and 94 parts by mass of commercially available LiNi _{0 . 5} Mn _{0 . 3} Co _{0 . 2} O ₂ particle|grains (average particle diameter of 5 micrometers) were dry-mixed, Then, 2 mass parts of polyvinylidene fluoride and an appropriate amount of N-methylpyrrolidone were wet-mixed, and the slurry was formed. After apply|coating this slurry on aluminum foil and drying it, the rolling process was performed and the positive electrode for lithium ion secondary batteries was obtained. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 3.80 g/cc. Moreover, using the obtained positive electrode, the lithium ion secondary battery was created in the procedure similar to Example 10, and DCIR was computed about the obtained battery.

Although the active material layer of the positive electrode in Example 10 and Example 11 has the same composition as the active material layer of the positive electrode in Example 5, the order of mixing of each component in the preparation process of an electrode material is different. In FIG. 18, the SEM photograph of 25000 times of the cross section of the positive electrode of Example 10 is shown. The SEM photograph of FIG. 18 is similar to the SEM photograph of the cross section of the positive electrode in Example 5 shown in FIG. 2B. That is, the grain boundaries of the primary carbon particles are not confirmed, and the carbon is in a paste-like form, and the paste-like carbon penetrates to the depths of pores (intervals between primary particles) having a width of 50 nm or less of the active material particles, so that the voids This almost doesn't exist. Moreover, 90% or more of the surfaces of the active material particles are in contact with paste-like carbon. Since fine carbon particles have poor compatibility with the binder and solvent, when preparing an electrode material in the form of a slurry containing the binder and solvent, after dry mixing the electrode active material particles and carbon as in the process of Example 5, the binder and Although adding a solvent and wet mixing is common, since the electrode density in the positive electrode of Example 10, Example 11, and Example 5 is substantially the same, and the observation result by an SEM photograph is similar, conductive carbon mixture is a binder and solvent, it was found that an electrode exhibiting similarly high electrode density even when wet-mixed with active material particles in the presence of a binder and a solvent was provided.

For the lithium ion secondary battery of Example 5 and the lithium ion secondary battery of Comparative Example 5 manufactured using only acetylene black as carbon, DCIR was measured in the same procedure as in Example 10, It compared with DCIR in the lithium ion secondary battery of 10 and Example 11. 19 shows the results. DCIR in the secondary battery of Example 5 is remarkably lower than DCIR in the secondary battery of Comparative Example 5, and it turns out that a remarkable reduction of DCIR is achieved by use of the electrode of this invention. Moreover, DCIR in the secondary battery of Example 10 and Example 11 is lower than DCIR in the secondary battery of Example 5, and a conductive carbon mixture is electroconductive irrespective of the mixing method of this mixture and electrode active material particle. It turns out that this excellent positive electrode is provided.

(ii) active material: LiCoO ₂

Example 12

4 parts by mass of the conductive carbon mixture obtained in Example 10, 2 parts by mass of polyvinylidene fluoride, and an appropriate amount of N-methylpyrrolidone are wet-mixed, and further 94 parts by mass of commercially available LiCoO ₂ particles (average particle size 10 μm) was added and wet-mixed to form a slurry. After apply|coating this slurry on aluminum foil and drying it, the rolling process was performed and the positive electrode for lithium ion secondary batteries was obtained. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 4.05 g/cc.

Example 13

4 parts by mass of the conductive carbon mixture obtained in Example 10 and 94 parts by mass of commercially available LiCoO ₂ particles (average particle diameter of 10 µm) were dry-mixed, followed by 2 parts by mass of polyvinylidene fluoride and an appropriate amount of N-methylpi Rollidone was wet mixed to form a slurry. After apply|coating this slurry on aluminum foil and drying it, the rolling process was performed and the positive electrode for lithium ion secondary batteries was obtained. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 4.05 g/cc.

Although the active material layer of the positive electrode in Example 12 and Example 13 has the same composition as the active material layer of the positive electrode in Example 7, the order of mixing of each component in the preparation process of an electrode material is different. Since the electrode density in the positive electrode of Example 12, Example 13, and Example 7 is the same, a conductive carbon mixture has good affinity with a binder and a solvent, Even if it wet-mixes with active material particle in presence of a binder and a solvent, similarly high electrode It was found to provide an electrode exhibiting density.

(iii) Change of carbon mixed with oxidation treated carbon

Example 14

The oxidation-treated carbon obtained in Example 1 and vapor-grown carbon fibers (average fiber diameter of 150 nm, average fiber length of 3.9 µm) were introduced into a ball mill at a mass ratio of 1:1, followed by dry mixing to obtain a conductive carbon mixture. Next, 4 parts by mass of the obtained conductive carbon mixture, 2 parts by mass of polyvinylidene fluoride, and an appropriate amount of N-methylpyrrolidone are wet-mixed, and further 94 parts by mass of commercially available LiNi _{0 . 5} Mn _{0 . 3} Co _{0 . 2} O ₂ particles (average particle diameter of 5 µm) were added and wet-mixed to form a slurry. After apply|coating this slurry on aluminum foil and drying it, the rolling process was performed and the positive electrode for lithium ion secondary batteries was obtained. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 3.66 g/cc.

Comparative Example 8

4 parts by mass of the vapor-grown carbon fiber used in Example 14, 2 parts by mass of polyvinylidene fluoride, and an appropriate amount of N-methylpyrrolidone were wet-mixed, and further 94 parts by mass of commercially available LiNi _{0 . 5} Mn _{0 . 3} Co _{0 . 2} O ₂ particles (average particle diameter of 5 µm) were added and wet-mixed to form a slurry. After apply|coating this slurry on aluminum foil and drying it, the rolling process was performed and the positive electrode for lithium ion secondary batteries was obtained. The electrode density was computed from the measured value of the volume and weight of the active material layer on the aluminum foil in this positive electrode. The value of the electrode density was 3.36 g/cc.

From the comparison of Example 14 and the comparative example 8, it turns out that an electrode density improves significantly by use of the conductive carbon mixture containing the oxidation-treated carbon obtained in Example 1.

Example 15

The procedure of Example 14 was repeated, except that graphene (length of 2 µm in the plane direction, length of several nm in the cross-sectional direction) was used instead of the vapor-grown carbon fibers. The value of the electrode density was 3.69 g/cc.

Comparative Example 9

The procedure of Comparative Example 8 was repeated except that the graphene used in Example 15 was used instead of the vapor-grown carbon fiber. The value of the electrode density was 3.45 g/cc.

From the comparison of Example 15 and the comparative example 9, it turns out that an electrode density improves significantly by use of the conductive carbon mixture containing the oxidation treatment carbon obtained in Example 1.

Example 16

The procedure of Example 14 was repeated except that furnace black (average particle diameter of 35 nm) was used instead of vapor-grown carbon fibers. The value of the electrode density was 3.76 g/cc.

Comparative Example 10

The procedure of Comparative Example 8 was repeated except that the furnace black used in Example 16 was used instead of the vapor-grown carbon fibers. The value of the electrode density was 3.42 g/cc.

From the comparison of Example 16 and the comparative example 10, it turns out that an electrode density improves significantly by use of the conductive carbon mixture containing the oxidation treatment carbon obtained in Example 1.

Example 17

The procedure of Example 14 was repeated except that graphite (average particle diameter of 6 µm) was used instead of vapor-grown carbon fibers. The value of the electrode density was 3.81 g/cc.

Comparative Example 11

The procedure of Comparative Example 8 was repeated except that the graphite used in Example 17 was used instead of the vapor-grown carbon fibers. The value of the electrode density was 3.48 g/cc.

From the comparison of Example 17 and the comparative example 11, it turns out that an electrode density improves significantly by use of the conductive carbon mixture containing the oxidation treatment carbon obtained in Example 1.

<Industrial Applicability>

By use of the electrode of the present invention, an electrical storage device having a high energy density is obtained.

Claims (12)

An electrode for a power storage device, comprising:
An active material layer comprising electrode active material particles and paste-like conductive carbon derived from oxidation-treated carbon that has been subjected to oxidation treatment to a carbon raw material having voids covering the surface of the electrode active material particles,
The paste is an electrode, characterized in that in the SEM photograph taken at a magnification of 25000 times, the grain boundary of the primary carbon particles is not confirmed, and means a state in which non-particulate amorphous carbon is connected. The method of claim 1,
The said active material layer further contains another conductive carbon, The electrode by which the surface of the conductive carbon is coat|covered with the said paste-form conductive carbon. 3. The method of claim 2,
The electrode whose mass ratio of the total amount of the said electrode active material particle in the said active material layer, the said paste-form conductive carbon, and the said other conductive carbon is the range of 95:5 - 99:1. 3. The method according to claim 1 or 2,
The said paste-form conductive carbon also exists in the inside of the hole which exists in the gap part formed between the width|variety of 50 nm or less, and the electrode active material particle|grains and/or the surface of the electrode active material particle adjacent. 3. The method of claim 1 or 2,
The electrode, wherein the active material layer has pores with a diameter of 5 to 40 nm. 3. The method according to claim 1 or 2,
The oxidation-treated carbon includes a hydrophilic portion, and the content of the hydrophilic portion is 10% by mass or more of the total oxidation-treated carbon,
The hydrophilic portion is obtained through a treatment in which 0.1 g of the oxidation-treated carbon is added to 20 mL of an aqueous ammonia solution having a pH of 11, followed by ultrasonic irradiation for 1 minute, and left for 5 hours to precipitate a solid portion. It is a part dispersed in an aqueous ammonia solution of pH 11,
The content of the hydrophilic part is determined by drying the remaining part from which the supernatant is removed after precipitation of the solid part, measuring the weight of the solid after drying, and subtracting the weight of the solid after drying from the weight of the initial oxidation-treated carbon 0.1 g The electrode obtained by calculating the weight ratio with respect to the weight of 0.1 g of the first oxidation-treated carbon. 3. The method according to claim 1 or 2,
The electrode with which 80% or more of the surface of the said electrode active material particle is contacting with the said paste-form conductive carbon. 3. The method according to claim 1 or 2,
The electrode active material particles are fine particles having an average particle diameter of 0.01 to 2 μm that can be operated as a positive electrode active material or a negative electrode active material, and coarse particles having an average particle diameter greater than 2 μm and less than or equal to 25 μm that can be operated as the same electrode active material as the fine particles. An electrode made of particles. A method for manufacturing the electrode according to claim 1 or 2, comprising:
By mixing the electrode active material particles and the oxidation-treated carbon subjected to oxidation treatment to the carbon raw material having voids, at least a part of the oxidation-treated carbon changes to a paste-like form to prepare an electrode material adhering to the surface of the electrode active material particles process, and
and a pressing step of forming an active material layer on a current collector with the electrode material and applying a pressure to the active material layer. 10. The method of claim 9,
The electrode material further comprises a different conductive carbon,
The preparation process is
By dry-mixing the oxidation-treated carbon and the other conductive carbon, at least a portion of the oxidation-treated carbon is changed to a paste-like form to obtain a conductive carbon mixture adhering to the surface of the other conductive carbon, and
By dry-mixing or wet-mixing the conductive carbon mixture and the electrode active material particles, the method of manufacturing an electrode, comprising the step of adhering the oxidation-treated carbon in which the at least part is changed to a paste form also on the surface of the electrode active material particles. As a conductive carbon mixture used as a conductive agent for manufacture of the electrode of an electrical storage device,
At least a portion derived from the oxidation-treated carbon that has been subjected to oxidation treatment to a carbon raw material having voids contains a paste-like conductive carbon, and conductive carbon different from the oxidation-treated carbon,
At least a portion of the conductive carbon paste is attached to the surface of the other conductive carbon,
The said paste form is a conductive carbon mixture characterized in that it means the state in which the grain boundary of a carbon primary particle is not confirmed, and non-particulate amorphous carbon is connected in the SEM photograph taken at 25000 times magnification. The electrical storage device provided with the electrode of Claim 1 or 2.

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