JP2014072128A - Active material particle for power storage device positive electrode, positive electrode for power storage device using the same, power storage device, and method for manufacturing active material particle for power storage device positive electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active material particle having high performance, which is excellent in rapid charge/discharge characteristics and has high energy density, and also to provide a battery positive electrode, a power storage device, and a method for manufacturing the active material particle.SOLUTION: An active material particle uses a conductive polymer as a base material and contains a conductive assistant. The active material particle for a power storage device positive electrode is put in a state where the conductive assistant is dispersed and included in a consecutive polymer base material.

Description

  The present invention relates to active material particles for power storage device positive electrodes, positive electrodes for power storage devices and power storage devices using the same, and a method for producing active material particles for power storage device positive electrodes. The present invention relates to a high-performance active material particle for a power storage device positive electrode, a positive electrode for a power storage device and a power storage device using the same, and a method for producing the active material particle for a power storage device positive electrode.

  In recent years, with the advancement and development of electronic technology in portable PCs, mobile phones, personal digital assistants (PDAs), secondary batteries that can be repeatedly charged and discharged are widely used as power storage devices for these electronic devices. Yes. In such an electrochemical storage device such as a secondary battery, it is desired to increase the capacity of a material used as an electrode.

  The electrode of the electricity storage device contains an active material having a function capable of inserting and removing ions. The insertion / desorption of ions of the active material is also referred to as so-called doping / dedoping, and the amount of doping / dedoping per certain molecular structure is called the doping rate (or doping rate). As a result, the capacity can be increased.

  Electrochemically, it is possible to increase the capacity of the battery by using a material having a large amount of ion insertion / extraction as an electrode. More specifically, lithium secondary batteries, which are attracting attention as power storage devices, use a graphite-based negative electrode that can insert and desorb lithium ions, and about one lithium ion is inserted per six carbon atoms. -Desorption and high capacity have been achieved.

  Among such lithium secondary batteries, a lithium-containing transition metal oxide such as lithium manganate or lithium cobaltate is used for the positive electrode, and a carbon material capable of inserting and removing lithium ions is used for the negative electrode. Lithium secondary batteries that face each other in an electrolytic solution have a high energy density, and thus are widely used as power storage devices for the electronic devices described above.

  However, the lithium secondary battery is a secondary battery that obtains electric energy by an electrochemical reaction, and has a drawback that the output density is low because the speed of the electrochemical reaction is low. Furthermore, since the internal resistance of the secondary battery is high, rapid discharge is difficult and rapid charge is also difficult. Moreover, since an electrode and electrolyte solution deteriorate by the electrochemical reaction accompanying charging / discharging, generally a lifetime, ie, a cycling characteristic, is not good.

  Therefore, in order to improve the above problem, a lithium secondary battery using a conductive polymer such as polyaniline having a dopant as a positive electrode active material is also known (see Patent Document 1).

  However, in general, a secondary battery having a conductive polymer as a positive electrode active material is an anion transfer type in which an anion is doped into the conductive polymer during charging and the anion is dedoped from the polymer during discharging. Therefore, when a carbon material that can insert and desorb lithium ions is used as the negative electrode active material, a cation-moving rocking chair type secondary battery in which cations move between both electrodes during charge and discharge cannot be configured. . That is, the rocking chair type secondary battery has the advantage that the amount of the electrolyte is small, but the secondary battery having the conductive polymer as the positive electrode active material cannot do so, and contributes to the miniaturization of the electricity storage device. I can't.

  In order to solve such problems, a large amount of electrolyte solution is not required, and the ion concentration in the electrolyte solution is not substantially changed, thereby improving the capacity density per volume, weight, and energy density. A cation migration type secondary battery has also been proposed. In this method, a positive electrode is formed using a conductive polymer having a polymer anion such as polyvinyl sulfonic acid as a dopant, and lithium metal is used for the negative electrode (see Patent Document 2).

Japanese Patent Laid-Open No. 3-129679 Japanese Patent Laid-Open No. 11132052

  However, the secondary battery is not yet sufficient in performance. In other words, this battery has a lower capacity density and energy density and sufficient quick charge / discharge characteristics than a lithium secondary battery using a lithium-containing transition metal oxide such as lithium manganate or lithium cobaltate for the positive electrode. Not.

  The present invention has been made in order to solve the above-described problems in an electricity storage device such as a conventional lithium secondary battery, and is excellent in rapid charge / discharge characteristics and has high energy density, active material particles, battery positive electrode, It is an object of the present invention to provide an electricity storage device and a method for producing active material particles.

  In order to achieve the above object, the present invention provides an active material particle containing a conductive polymer as a base material and containing a conductive auxiliary agent, wherein the conductive auxiliary agent is dispersed and encapsulated in the conductive polymer base material. Let the active material particle for electrical storage device positive electrodes which become the 1st summary.

  Also, a battery positive electrode using active material particles containing a conductive polymer as a base material and containing a conductive assistant, wherein the conductive assistant is dispersed and encapsulated in the conductive polymer base material. The positive electrode for devices is the second gist.

  Furthermore, an electricity storage device having an electrolyte layer and a positive electrode and a negative electrode provided to face each other with the electrolyte layer interposed therebetween, wherein at least a conductive additive is dispersed and encapsulated in a base material made of a conductive polymer. An electricity storage device using the active material particles is a third aspect.

  A method for producing active material particles in which at least a conductive additive is dispersed and encapsulated in a base material made of a conductive polymer, wherein at least the conductive polymer and the conductive aid are sheared using a pulverizing and mixing device. The manufacturing method of the active material particles for the electricity storage device positive electrode to be performed is a fourth gist.

  That is, the present inventors have intensively studied in order to obtain a high-performance power storage device having excellent rapid charge / discharge characteristics and a high energy density. In the process, the present inventors paid attention to a conductive polymer that is an active material, and further studied this. As a result of various experiments, the inventors have found that it is possible to realize surprisingly high rapid charge / discharge characteristics by using active material particles containing a conductive polymer as a base material and containing a conductive auxiliary agent, and reached the present invention. The reason for this is not necessarily clear, but it is presumed that a conductive path is formed inside the particles by kneading the conductive assistant into the conductive polymer as the active material, thereby improving the rapid charge / discharge characteristics. The

  As described above, the active material particles containing a conductive polymer as a base material and containing a conductive auxiliary agent, wherein the conductive auxiliary agent is dispersed and encapsulated in the conductive polymer base material. When it is an active material particle, an electricity storage device using the particle has excellent rapid charge / discharge characteristics and a high energy density.

  In addition, when the conductive auxiliary agent is an active material particle for a power storage device positive electrode that is 1 to 30 parts by weight with respect to 100 parts by weight of the conductive polymer, the power storage device using the same further improves rate characteristics, Excellent rapid charge / discharge characteristics.

  Furthermore, when the conductive polymer is an active material particle for a power storage device positive electrode made of polyaniline, the power storage device using the power storage device has a higher capacity density.

  A battery positive electrode using active material particles having a conductive polymer as a base material and containing a conductive auxiliary agent, wherein the conductive auxiliary agent is dispersed and encapsulated in the conductive polymer base material. When it is a positive electrode for a device, an electricity storage device using the positive electrode is excellent in rapid charge / discharge characteristics and has a high energy density.

  In addition, when the conductive auxiliary agent is a positive electrode for a power storage device having 1 to 30 parts by weight with respect to 100 parts by weight of the conductive polymer, the power storage device using the same further improves rate characteristics, and quick charge / discharge Excellent characteristics.

  Furthermore, when the conductive polymer is a positive electrode for an electricity storage device in which polyaniline is used, the electricity storage device using the same further improves the capacity density.

  An electrical storage device having an electrolyte layer and a positive electrode and a negative electrode provided to face each other with the electrolyte layer interposed therebetween, wherein the positive electrode is dispersed and encapsulated in a base material made of a conductive polymer. The power storage device using the active material particles is excellent in rapid charge / discharge characteristics and has a high energy density.

  Moreover, when it is an electrical storage device whose compounding quantity of the said conductive support agent is 1-30 weight part with respect to 100 weight part of conductive polymers, a rate characteristic improves further and it comes to be excellent in a quick charge / discharge characteristic.

  Furthermore, when the conductive polymer is a power storage device made of polyaniline, the capacity density is further improved.

  A method for producing active material particles in which at least a conductive auxiliary agent is dispersed and encapsulated in a base material made of a conductive polymer, wherein at least the conductive polymer and the conductive auxiliary agent are sheared using a pulverization mixing device When the method for producing active material particles for device positive electrode is used, the conductive auxiliary agent is easily kneaded into the conductive polymer, and the electric storage device using the active material particles for electric storage device positive electrode obtained thereby has rapid charge / discharge characteristics. And has a high energy density.

It is sectional drawing which shows an example of the electrical storage device of this invention. (A) And (B) shows the transmission electron microscope (TEM) photograph which image | photographed the positive electrode cross section of Example 1 and the comparative example 1, respectively with high magnification. Portions surrounded by chain lines (A) and (B) are diagrams schematically showing positive electrode cross sections of Example 1 and Comparative Example 1, respectively. A small black dot indicates a conductive aid, and an elliptical particle indicated by a larger solid line indicates a conductive polymer. In (A), the conductive aid is dispersed in the conductive polymer. (A) and (B) show the transmission electron microscope (TEM) photograph which image | photographed the positive electrode cross section of Example 1 and the comparative example 1 at low magnification, respectively, in order to show the said FIG.

  Hereinafter, embodiments of the present invention will be described in detail. However, the description described below is an example of embodiments of the present invention, and the present invention is not limited to the following contents.

  The active material particles for an electricity storage device positive electrode of the present invention (hereinafter, sometimes simply abbreviated as “active material particles”) are active material particles having a conductive polymer as a base material and containing a conductive additive, The agent is characterized by being dispersed and encapsulated in a conductive polymer base material. And the said active material particle is used for the positive electrode for electrical storage devices, for example, as shown in FIG. 1, the electrical storage device which has the electrolyte layer 3, and the positive electrode 2 and the negative electrode 4 which were provided facing on both sides of this The positive electrode 2 is used. In FIG. 1, reference numeral 1 is a positive electrode current collector, and reference numeral 5 is a negative electrode current collector. Such a positive electrode, an electrolyte layer, and a negative electrode are demonstrated in order below.

<About positive electrode>
As described above, the positive electrode for an electricity storage device of the present invention contains the active material particles. That is, the positive electrode of the present invention uses, as a positive electrode constituent material, active material particles in which at least a conductive additive is dispersed and encapsulated in a base material made of a conductive polymer.

[About active material particles]
First, the conductive polymer that is the base material of the active material particles of the present invention will be described. A conductive polymer is a polymer itself that is inserted or desorbed from the polymer in order to compensate for the change in charge generated or lost by the oxidation or reduction reaction of the polymer main chain. A group of polymers whose electrical conductivity changes.

  In such a polymer, a state with high conductivity is referred to as a doped state, and a state with low conductivity is referred to as a dedope state. Even if a polymer having conductivity loses conductivity by an oxidation reaction or a reduction reaction and becomes insulative (that is, in a dedoped state), such a polymer is reversibly conductive again by the oxidation-reduction reaction. Therefore, the insulating polymer in such a dedope state is also included in the category of the conductive polymer in the present invention.

  Preferred examples of the conductive polymer of the present invention include at least one proton acid anion selected from the group consisting of an inorganic acid anion, a fatty acid sulfonate anion, an aromatic sulfonate anion, a polymer sulfonate anion, and a polyvinyl sulfate anion. The polymer which has as a dopant is mention | raise | lifted. Further, another conductive polymer preferable in the present invention is a polymer in a dedope state obtained by dedoping the conductive polymer.

  Specific examples of the conductive polymer include, for example, polyacetylene, polypyrrole, polyaniline, polythiophene, polyfuran, polyselenophene, polyisothianaphthene, polyphenylene sulfide, polyphenylene oxide, polyazulene, and poly (3,4-ethylenedioxythiophene). And conductive polymer materials such as the above-described substituted polymers, or carbon materials such as polyacene, graphite, carbon nanotube, carbon nanofiber, and graphene. Of these, polyaniline, polyaniline derivatives, polypyrrole, and polypyrrole derivatives having a large electrochemical capacity are preferably used, and polyaniline and polyaniline derivatives are more preferably used.

  In the present invention, the polyaniline means a polymer obtained by electrolytic polymerization or chemical oxidative polymerization of aniline, and the polyaniline derivative is obtained by electrolytic polymerization or chemical oxidative polymerization of an aniline derivative, for example. Refers to the polymer produced.

  More specifically, as a derivative of aniline, a substituent such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group, an aryloxy group, an alkylaryl group, an arylalkyl group, or an alkoxyalkyl group is provided at a position other than the 4-position of aniline. What has at least one can be illustrated. Preferable specific examples include, for example, o-substituted anilines such as o-methylaniline, o-ethylaniline, o-phenylaniline, o-methoxyaniline, o-ethoxyaniline, m-methylaniline, m-ethylaniline, m And m-substituted anilines such as -methoxyaniline, m-ethoxyaniline, m-phenylaniline and the like. These may be used alone or in combination of two or more. In the present invention, p-phenylaminoaniline having a substituent at the 4-position can be suitably used as an aniline derivative because polyaniline is obtained by oxidative polymerization.

  Hereinafter, unless otherwise specified, in the present invention, “aniline or a derivative thereof” is simply referred to as “aniline”, and “at least one of polyaniline and a polyaniline derivative” is simply referred to as “polyaniline”. Therefore, even when the polymer constituting the conductive polymer is obtained from an aniline derivative, it may be referred to as “conductive polyaniline”.

  Furthermore, the active material particles of the present invention are in a state in which a conductive additive is dispersed and encapsulated in the conductive polymer base material. Therefore, the conductive aid will be described.

  The conductive auxiliary agent may be any conductive material whose properties do not change depending on the potential applied during the discharge of the electricity storage device, and examples thereof include conductive carbon materials and metal materials, among which acetylene black and ketjen black A conductive carbon black such as carbon fiber, or a fibrous carbon material such as carbon fiber or carbon nanotube is preferably used. Particularly preferred is conductive carbon black.

  It is preferable that the said conductive support agent is 1-30 weight part with respect to 100 weight part of said conductive polymers, More preferably, it is 4-20 weight part, Especially preferably, it is 8-18 weight part. When the blending amount of the conductive assistant is within this range, the shape and characteristics as the active material can be prepared without any abnormality, and the rate characteristics can be effectively improved.

  The active material particles of the present invention can be obtained, for example, by subjecting the above-mentioned conductive polymer and conductive auxiliary agent (and a solvent or other additives as necessary) to a shearing treatment using a pulverizing and mixing device. Examples of the pulverizing and mixing apparatus include a dry ball mill, a wet ball mill, a bead mill, an attritor, a JET mill atomizer, and a dry ball mill is preferably used.

  In addition, the diameter of the pulverized ball used in the ball mill method is preferably 0.1 to 10 mm, more preferably 1 to 7 mm from the viewpoint that an appropriate shearing treatment can be performed.

  The active material particles of the present invention preferably have a median diameter of 0.001 to 1000 μm, more preferably 0.01 to 100 μm, and particularly preferably 0.1 to 20 μm. The median diameter can be measured using, for example, a dynamic light scattering particle size distribution measuring apparatus.

  In addition to the above active material particles, a binder, a conductive additive, water, and the like can be appropriately added to the positive electrode material of the present invention as necessary. In particular, it is preferable to have an anionic material that also functions as a binder in terms of improving the capacity density.

  Examples of the anionic material include a polymer anion, an anion compound having a relatively large molecular weight, and an anion compound having low solubility in an electrolytic solution. More specifically, a compound having a carboxyl group in the molecule is preferably used, and a polycarboxylic acid which is a polymer is particularly preferably used. When polycarboxylic acid is used as the anionic material, since the polycarboxylic acid functions as a binder and also functions as a dopant, the characteristics of the electricity storage device are improved.

  Examples of the polycarboxylic acid include polyacrylic acid, polymethacrylic acid, polyvinylbenzoic acid, polyallylbenzoic acid, polymethallylbenzoic acid, polymaleic acid, polyfumaric acid, polyglutamic acid, and polyaspartic acid. Methacrylic acid is particularly preferably used. These may be used alone or in combination of two or more.

  As said polycarboxylic acid, what makes the carboxylic acid of the compound which has a carboxyl group in a molecule | numerator a lithium type is mention | raise | lifted. The exchange rate for the lithium type is preferably 100%, but the exchange rate may be low depending on the situation, and is preferably 40% to 100%.

  The anionic material is usually used in an amount of 1 to 100 parts by weight, preferably 2 to 70 parts by weight, and most preferably 5 to 40 parts by weight with respect to 100 parts by weight of the conductive polymer. If the amount of the anionic material with respect to the conductive polymer is too small, it tends to be impossible to obtain an electricity storage device with excellent capacity density. On the other hand, if the amount of the anionic material with respect to the conductive polymer is too large, as a result There is a tendency that the active material is reduced and an electricity storage device having a high capacity density cannot be obtained.

  In addition to the anionic material, examples of the binder used together with the conductive polymer include vinylidene fluoride.

  In addition, examples of the optional conductive assistant that is appropriately added to the positive electrode material according to the present invention include those similar to the conductive assistant used for the active material particles. Any conductive material whose properties do not change depending on the potential applied during the discharge of the electricity storage device, such as a conductive carbon material, a metal material, and the like, among them, conductive carbon black such as acetylene black and ketjen black, Fibrous carbon materials such as carbon fibers and carbon nanotubes are preferably used. Particularly preferred is conductive carbon black.

  In addition, although the conductive support agent here means the conductive support agent of the arbitrary components used separately from the conductive support agent for active material particles disperse | distributed to a conductive polymer base material as an active material particle material mentioned above, active material particle | grains The conductive material may be the same material or different.

  The optional conductive assistant is preferably 1 to 30 parts by weight, more preferably 4 to 20 parts by weight, and 8 to 18 parts by weight with respect to 100 parts by weight of the conductive polymer. Is particularly preferred.

<Positive electrode>
The positive electrode for an electricity storage device of the present invention is preferably composed of a composite of the above conductive polymer and an anionic material, and is usually formed on a porous sheet.

  The thickness of the positive electrode is usually 1 to 500 μm, preferably 10 to 300 μm. The thickness of the positive electrode can be calculated, for example, by measuring using a dial gauge (manufactured by Ozaki Mfg. Co., Ltd.), which is a flat plate having a tip shape of 5 mm in diameter, and calculating the average of 10 measured values with respect to the surface of the electrode. . In addition, when the positive electrode (porous layer) is provided on the current collector and composited, the thickness of the composite is measured in the same manner as described above, and the average of the measured values is obtained. From this value, the current collector is obtained. The thickness of the positive electrode is determined by subtracting the thickness of the positive electrode.

  The positive electrode for an electricity storage device of the present invention is formed, for example, as follows. A slurry is prepared by adding at least a conductive additive, a binder, and water to the positive electrode active material particles containing the conductive polymer and sufficiently dispersing the slurry. And after apply | coating this on a collector, the said slurry is shaped in a sheet form by evaporating water. Thereby, the positive electrode (sheet electrode) which consists of a composite body which has a layer of a mixture of a conductive polymer, an anionic material etc. which are added as needed on a collector can be obtained.

<Electrolyte layer>
The electrolyte layer described above is composed of an electrolyte. For example, a sheet obtained by impregnating a separator with an electrolytic solution or a sheet made of a solid electrolyte is preferably used. The sheet made of the solid electrolyte itself also serves as a separator.

The electrolyte is composed of a solute and, if necessary, a solvent and various additives. Examples of the solute include metal ions such as lithium ions and appropriate counter ions corresponding thereto, such as sulfonate ions, perchlorate ions, tetrafluoroborate ions, hexafluorophosphate ions, hexafluoroarsenic ions, bis A combination of (trifluoromethanesulfonyl) imide ion, bis (pentafluoroethanesulfonyl) imide ion, halogen ion and the like is preferably used. Specific examples of the electrolyte include LiCF ₃ SO ₃ , LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiCl, and the like. Can do.

  As the solvent, for example, at least one non-aqueous solvent such as carbonates, nitriles, amides, ethers, that is, an organic solvent is used. Specific examples of such an organic solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, propionitrile, N, N'-dimethylacetamide, N-methyl-2- Examples include pyrrolidone, dimethoxyethane, diethoxyethane, and γ-butyrolactone. These may be used alone or in combination of two or more. In addition, what melt | dissolved the solute in the solvent may be called "electrolyte solution."

<Separator>
In the present invention, as described above, the separator can be used in various modes. As the separator, it is possible to prevent an electrical short circuit between the positive electrode and the negative electrode that are arranged to face each other across the separator. Furthermore, the separator is electrochemically stable, has a large ion permeability, and has a certain level. Any insulating porous sheet having mechanical strength may be used. Therefore, as the material of the separator, for example, a porous film made of paper, nonwoven fabric, or a resin such as polypropylene, polyethylene, or polyimide is preferably used, and these are used alone or in combination of two or more.

<Negative electrode>
The negative electrode described above is preferably formed using a negative electrode material (negative electrode active material) capable of inserting / extracting metal or ions. As the negative electrode active material, metallic lithium, a carbon material in which lithium ions can be inserted / extracted during oxidation / reduction, a transition metal oxide, silicon, tin, or the like is preferably used. Note that the thickness of the negative electrode preferably conforms to the thickness of the positive electrode.

<Positive electrode current collector, negative electrode current collector>
Here, the positive electrode current collector 1 and the negative electrode current collector 5 in FIG. 1 will be described. Examples of materials for these current collectors include metal foils such as nickel, aluminum, stainless steel, and copper, and meshes. Note that the positive electrode current collector and the negative electrode current collector may be formed of the same material or different materials.

<Power storage device>
Next, an electricity storage device using the positive electrode for an electricity storage device of the present invention will be described. As the electricity storage device of the present invention, for example, as shown in FIG. 1, there is a device having an electrolyte layer 3 and a positive electrode 2 and a negative electrode 4 provided to face each other with the electrolyte layer 3 interposed therebetween.

  An electricity storage device using the positive electrode for an electricity storage device of the present invention can be produced, for example, as follows using the material such as the negative electrode. That is, lamination is performed such that a separator is disposed between the positive electrode and the negative electrode, a laminate is produced, and the laminate is placed in a battery container such as an aluminum laminate package, and then vacuum dried. Next, an electrolytic solution is poured into a vacuum-dried battery container, and a package that is a battery container is sealed, whereby an electricity storage device can be manufactured. In addition, it is preferable to manufacture batteries, such as electrolyte solution injection | pouring to a package, in inert gas atmosphere, such as ultrapure argon gas, in a glove box.

  The electricity storage device of the present invention is formed into various shapes such as a film type, a sheet type, a square type, a cylindrical type, and a button type in addition to the laminate cell. Moreover, as a positive electrode size of an electrical storage device, in the case of a laminate cell, one side is preferably 1 to 300 mm, particularly preferably 10 to 50 mm, and a negative electrode size is 1 to 400 mm. It is preferably 10 to 60 mm. The electrode size of the negative electrode is preferably slightly larger than the positive electrode size.

  Moreover, the electricity storage device of the present invention is excellent in weight output density and cycle characteristics like an electric double layer capacitor, and has a weight energy density much higher than that of a conventional electric double layer capacitor. Therefore, it can be said that the electricity storage device of the present invention is a capacitor electricity storage device.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples.

  First, prior to the production of electricity storage devices as examples and comparative examples, the following components were prepared and prepared.

<Preparation of conductive polyaniline powder>
Conductive polyaniline (conductive polymer) powder using tetrafluoroboric acid as a dopant was prepared as follows. That is, 84.0 g (0.402 mol) of a 42 wt% aqueous tetrafluoroboric acid solution (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent) was added to a 300 mL glass beaker containing 138 g of ion-exchanged water. While stirring with a stirrer, 10.0 g (0.107 mol) of aniline was added thereto. When aniline was first added to the tetrafluoroboric acid aqueous solution, the aniline was dispersed as oily droplets in the tetrafluoroboric acid aqueous solution. Became. The aniline aqueous solution thus obtained was cooled to −4 ° C. or lower using a low temperature thermostat.

  Next, 11.63 g (0.134 mol) of manganese dioxide powder (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade 1) as an oxidizing agent is added little by little to the aniline aqueous solution, and the temperature of the mixture in the beaker is −1. The temperature was not exceeded. Thus, by adding an oxidizing agent to the aniline aqueous solution, the aniline aqueous solution immediately turned black-green. Thereafter, when stirring was continued for a while, a black-green solid started to be formed.

  Thus, after adding an oxidizing agent over 80 minutes, it stirred for further 100 minutes, cooling the reaction mixture containing the produced | generated reaction product. Then, using a Buchner funnel and a suction bottle, the obtained solid was No. The powder was obtained by suction filtration with 2 filter papers. The powder was stirred and washed in an aqueous solution of about 2 mol / L tetrafluoroboric acid using a magnetic stirrer. Then, the mixture was washed with stirring several times with acetone and filtered under reduced pressure. The obtained powder was vacuum-dried at room temperature (25 ° C.) for 10 hours to obtain 12.5 g of conductive polyaniline (hereinafter simply referred to as “conductive polyaniline”) having tetrafluoroboric acid as a dopant. The conductive polyaniline was a bright green powder.

(Conductivity of conductive polyaniline powder)
After pulverizing 130 mg of the conductive polyaniline powder in a smoked mortar, vacuum pressure molding was performed for 10 minutes under a pressure of 75 MPa using a KBr tablet molding machine for infrared spectrum measurement, and the conductive polyaniline having a diameter of 13 mm and a thickness of 720 μm Got the disc. The conductivity of the disk measured by the 4-terminal conductivity measurement by the Van der Boe method was 19.5 S / cm.

(Preparation of dedope conductive polyaniline powder)
The conductive polyaniline powder in the doped state obtained above is placed in a 2 mol / L aqueous sodium hydroxide solution and stirred in a 3 L separable flask for 30 minutes, and the tetrafluoroboric acid as a dopant is removed by a neutralization reaction. Doped. The dedoped polyaniline was washed with water until the filtrate became neutral, then stirred and washed in acetone, and filtered under reduced pressure using a Buchner funnel and a suction bottle to obtain a dedoped polyaniline powder on No. 2 filter paper. . This was vacuum-dried at room temperature for 10 hours to obtain a brown undoped polyaniline powder.

(Preparation of polyaniline powder in reduced dedoped state)
Next, this dedope polyaniline powder was put into a methanol solution of phenylhydrazine and subjected to reduction treatment for 30 minutes with stirring. The color of the polyaniline powder changed from brown to gray by reduction. After the reaction, it was washed with methanol, washed with acetone, filtered, and vacuum dried at room temperature to obtain polyaniline in a reduced and dedoped state.
The median diameter of the particles by light scattering method using acetone as a solvent was 13 μm.

(Conductivity of polyaniline powder in reduced and undoped state)
After pulverizing 130 mg of the above polyaniline powder in the reduced dedope state in a smoked mortar, vacuum reduced pressure molding was performed for 10 minutes under a pressure of 75 MPa using a KBr tablet molding machine for infrared spectrum measurement, and a reduced dedope having a thickness of 720 μm. A polyaniline disk in state was obtained. The electrical conductivity of the disk measured by the 4-terminal conductivity measurement by the Van der Boe method was 5.8 × 10 ⁻³ S / cm. Thus, it can be said that the polyaniline compound is an active material compound whose conductivity is changed by ion insertion / extraction.

<Preparation of polycarboxylic acid>
4.4 g of polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 1,000,000) was dissolved in ion-exchanged water to obtain 20.5 g of a 4.4% by weight viscous polyacrylic acid aqueous solution. Next, 0.15 g of lithium hydroxide was added to the obtained polyacrylic acid aqueous solution and dissolved again to prepare a polyacrylic acid-polylithium acrylate complex solution in which 50% of the acrylic acid sites were substituted with lithium.

<Preparation of separator>
A nonwoven fabric (manufactured by Hosen Co., Ltd., TF40-50 (porosity: 55%)) was prepared.

<Preparation of negative electrode>
Metal lithium having a thickness of 50 μm (Honjo Metal Co., Ltd., rolled metal lithium) was prepared.

<Preparation of electrolyte>
An ethylene carbonate / dimethyl carbonate solution (manufactured by Kishida Chemical Co., Ltd.) of 1 mol / dm ³ concentration of lithium tetrafluoroborate (LiBF ₄ ) was prepared.

<Tab electrode>
An aluminum metal foil with a thickness of 50 μm was prepared as a tab electrode for current extraction of the positive electrode, and a nickel metal foil with a thickness of 50 μm was prepared as a tab electrode for current extraction of the negative electrode.

<Current collector>
An aluminum foil with a thickness of 30 μm was prepared as a current collector for positive electrode, and a stainless mesh with a thickness of 180 μm was prepared as a current collector for negative electrode.

  First, a positive electrode slurry for preparing a positive electrode was prepared using the prepared material.

[Slurry for Example 1]
(Preparing active material particles)
Using a dry ball mill (Fritsch, planetary ball mill P-6 using 5 mm zirconia balls), 0.5 g of a conductive additive (Denka Black, manufactured by Denki Kagaku Kogyo) and 4 g of the polyaniline powder obtained above were used. By conducting the treatment at 400 rpm, conductive assistant-containing polyaniline particles, which are active material particles according to the present invention, were obtained.

(Slurry preparation)
4 g of the conductive auxiliary agent-containing polyaniline particles are further mixed with 0.5 g of conductive auxiliary agent (Denka Black, Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.) and 4 g of water, and then mixed with the polyacrylic acid-lithium lithium acrylate composite. Add to 20.5 g of body solution and knead well with a spatula, then sonicate for 5 minutes with an ultrasonic homogenizer, and then have fluidity using Fillmix 40-40 (Plymix) A slurry was obtained. This slurry was defoamed for 3 minutes using Awatori Nertaro (manufactured by Shinky Corporation).

[Slurry for Comparative Example 1]
Similar to the preparation of the slurry for Example 1, except that 4 g of the polyaniline powder in which the conductive auxiliary agent was not kneaded was used instead of 4 g of the conductive auxiliary agent-containing polyaniline particles used at the time of preparing the slurry for Example 1. A slurry was prepared.

[Slurry for Comparative Example 2]
A slurry was prepared in the same manner as in the preparation of the slurry for Comparative Example 1, except that 0.5 g of the conductive assistant used in preparing the slurry for Comparative Example 1 was increased to 1.0 g of the conductive assistant.

[Example 1, Comparative Examples 1 and 2]
Next, the slurry for Example 1 and the slurry for Comparative Examples 1 and 2 (defoamed slurry) obtained above were respectively used in a table type automatic coating apparatus (manufactured by Tester Sangyo Co., Ltd.), and a doctor blade with a micrometer. The coating thickness of the solution was adjusted to 360 μm with a type applicator, and the coating was applied onto an etching aluminum foil for an electric double layer capacitor (manufactured by Hosen Co., Ltd., 30CB) at a coating speed of 10 mm / second. Subsequently, it dried for 20 minutes with the dryer of temperature 150 degreeC, and produced the polyaniline sheet electrode, and the positive electrode of Example 1, Comparative Example 1 and 2 was obtained.

  Here, in order to observe the dispersion state of the active material particles and the conductive additive in the positive electrode in the produced positive electrode, a cross-sectional TEM measurement of the positive electrode was performed. After embedding the positive electrode in a resin so that the embedding resin spreads in the voids in the positive electrode, a cross section of the electrode is cut out by an ultrathin section method, and the ultrathin section is obtained by a transmission electron microscope (TEM: manufactured by Hitachi High-Tech, H- 7650), cross-sectional images of the positive electrode as shown in FIGS.

  2A and 2B show TEM photographs at high magnification (25,000 times) of positive electrode cross sections of Example 1 and Comparative Example 1, respectively. 3A and 3B are diagrams schematically showing the positive electrodes of Example 1 and Comparative Example 1 in the TEM photographs of FIGS. 2A and 2B. Small black spots are conductive aids, and larger particles are active material particles.

  From the comparison between FIGS. 2 and 3 (A) and (B), in the active material particles in the positive electrode of Example 1, the conductive auxiliary agent is dispersed and encapsulated in the conductive polymer. I understand that.

  4A and 4B show TEM photographs of the positive electrode cross sections of Example 1 and Comparative Example 1 at a low magnification (5,000 times). At low magnification, it is impossible to observe the state where the conductive auxiliary agent is dispersed and encapsulated in the conductive polymer, but the shape of each active material particle can be observed. Note that the fine spherical particles such as wrinkles commonly seen in FIGS. 2 and 4 are conductive assistants (carbon black) and not conductive polymers.

<Production of electricity storage device>
Using the positive electrode (polyaniline sheet electrode) of Example 1 and Comparative Examples 1 and 2 obtained as described above and the other materials prepared above, an assembly of a laminate cell as an electricity storage device (lithium secondary battery) is shown below. .

  The battery was assembled in a glove box under an ultra-high purity argon gas atmosphere (dew point in the glove box: −100 ° C.).

  Moreover, the electrode size of the positive electrode for laminate cells is 27 mm × 27 mm, the negative electrode size is 29 mm × 29 mm, which is slightly larger than the positive electrode size.

  First, the metal foils of the positive electrode tab electrode and the negative electrode tab electrode were respectively connected to the corresponding current collectors beforehand using a spot welder. A polyaniline sheet electrode (positive electrode), a stainless mesh prepared as a negative electrode current collector, and a separator were vacuum-dried at 80 ° C. for 2 hours. Then, it puts into a glove box with a dew point of −100 ° C., and in the glove box, the prepared metal lithium foil was pressed against the stainless steel mesh of the current collector to form a composite of the negative electrode and the current collector. .

  Next, in the glove box, put a separator between the positive electrode and the negative electrode, set them in a laminate cell that is heat-sealed on three sides, and make sure that the positive electrode and the negative electrode face each other correctly and do not short-circuit. The position of the separator was also adjusted, and a sealing agent was set on the positive electrode and negative electrode tab portions, and the tab electrode portion was heat-sealed leaving a little electrolyte inlet. Thereafter, a predetermined amount of electrolyte is sucked with a micropipette, and a predetermined amount is injected from the electrolyte solution inlet of the laminate cell. Finally, the electrolyte solution inlet at the top of the laminate cell is sealed by heat sealing to complete the laminate cell.

  Various properties were measured and evaluated using each laminate cell (electric storage device) thus obtained according to the following measurement method, and the results are shown in Table 1 below.

<Measurement of energy density (mWh / g)>
Each power storage device was subjected to energy density measurement in a constant current / constant voltage charge / constant current discharge mode in a 25 ° C. environment using a battery charging / discharging device (SD8 manufactured by Hokuto Denko). The end-of-charge voltage is 3.8 V. After the voltage reaches 3.8 V by constant current charging, constant voltage charging at 3.8 V is performed for 2 minutes, and then constant current discharge is performed until the end-of-discharge voltage is 2.0 V. went. The weight capacity density of polyaniline was set to 150 mAh / g, and the total capacity density (mAh) was calculated from the amount of polyaniline contained in the electrode unit area of each power storage device, and was set to charge / discharge the entire capacity in 20 hours (0 .05C).

<Measurement of rate characteristics (%)>
(10C / 0.2C rate characteristics (%))
The rate characteristic (%) is obtained by charging / discharging at 0.2 C in a constant current / constant voltage charging / constant current discharging mode using a battery charging / discharging device (SD8, manufactured by Hokuto Denko), Charge and discharge at 10 C to obtain the discharge capacity. The value obtained by “discharge capacity at 10 C / discharge capacity at 0.2 C × 100” was defined as the rate characteristic (%) of 10 C / 0.2 C.

(100C / 0.2C rate characteristics (%))
Next, in the measurement of the rate characteristics of 10C / 0.2C, the discharge capacity was obtained in the same manner except that charge / discharge was performed by replacing 10C with 100C, and this was calculated as “discharge capacity at 100C / The value obtained by “discharge capacity at 0.2 C × 100” was defined as the rate characteristic (%) of 100 C / 0.2 C.

  Here, “0.2C” means a current value at which charging or discharging is completed after 5 hours of constant current charging or discharging using the assembled secondary battery, and “10C” is It means a current value at which charging or discharging ends in 6 minutes after constant current charging or discharging, and “100C” is a current value at which charging or discharging ends after 36 seconds of constant current charging or discharging. Means that.

  Example 1 in Table 1 shows a value as high as 80% in the rate characteristics of 10C / 0.2C, and further shows a charge / discharge maintenance rate of 34% even under severe conditions of 100C / 0.2C. From the above, it was found that the examples of the present invention have high charge / discharge characteristics.

  On the other hand, in Comparative Examples 1 and 2 using conductive polyaniline that does not include a conductive additive as an active material, the rate characteristics of 10C / 0.2C are both about 50%, and 100C / 0.2C. In terms of rate characteristics, both showed a low charge / discharge maintenance rate of about 10%. From this, it was found that when the positive electrode using the active material particles of the present invention was used, the obtained electricity storage device had high charge / discharge characteristics. In addition, all of Examples and Comparative Examples showed high weight energy density, and thus, it was found that even if the conductive auxiliary agent was inherent in the active material particles, it still had high weight energy density.

  The electricity storage device of the present invention can be suitably used as an electricity storage device such as a lithium secondary battery. The power storage device of the present invention can be used for the same applications as conventional secondary batteries. For example, portable electronic devices such as portable PCs, mobile phones, and personal digital assistants (PDAs), hybrid electric vehicles, Widely used in power sources for driving automobiles, fuel cell vehicles and the like.

DESCRIPTION OF SYMBOLS 1 Current collector for positive electrodes 2 Positive electrode 3 Electrolyte layer 4 Negative electrode 5 Current collector for negative electrodes

Claims (10)

  An active material particle having a conductive polymer as a base material and containing a conductive auxiliary agent, wherein the conductive auxiliary agent is dispersed and encapsulated in the conductive polymer base material. Active material particles.   The active material particles for an electricity storage device positive electrode according to claim 1, wherein the conductive auxiliary agent is 1 to 30 parts by weight with respect to 100 parts by weight of the conductive polymer.   The active material particle for an electricity storage device positive electrode according to claim 1 or 2, wherein the conductive polymer is polyaniline.   A battery positive electrode using active material particles comprising a conductive polymer as a base material and containing a conductive aid, wherein the conductive aid is dispersed and encapsulated in the conductive polymer base material. A positive electrode for an electricity storage device.   The positive electrode for an electricity storage device according to claim 4, wherein the conductive additive is 1 to 30 parts by weight with respect to 100 parts by weight of the conductive polymer.   The positive electrode for an electricity storage device according to claim 4 or 5, wherein the conductive polymer is polyaniline.   An electricity storage device having an electrolyte layer and a positive electrode and a negative electrode provided to face each other with the electrolyte layer interposed therebetween, wherein the positive electrode is an active material in which at least a conductive additive is dispersed and encapsulated in a base material made of a conductive polymer. An electricity storage device comprising material particles.   The electricity storage device according to claim 7, wherein the compounding amount of the conductive assistant is 1 to 30 parts by weight with respect to 100 parts by weight of the conductive polymer.   The electricity storage device according to claim 7 or 8, wherein the conductive polymer is polyaniline. A method of producing active material particles in which at least a conductive additive is dispersed and encapsulated in a base material made of a conductive polymer, wherein at least the conductive polymer and the conductive aid are sheared using a pulverization and mixing device The manufacturing method of the active material particle for electrical storage device positive electrodes characterized by these.