JP2015099663A - Conductive polymer particle and production method therefor, and positive electrode for power storage device using the same and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide conductive polymer particles excellent in capacity density and a production method therefor, and to provide a positive electrode for power storage device using the same and a manufacturing method therefor.SOLUTION: Conductive polymer particles, where the particle surface is modified by protonic acid treatment, are used as a formation material of a positive electrode for power storage device.

Description

  TECHNICAL FIELD The present invention relates to conductive polymer particles that are components constituting a high-performance positive electrode for an electricity storage device having high charge / discharge efficiency, a method for producing the same, and a positive electrode for an electricity storage device using the same and a method for producing the same.

  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 electrochemical storage devices such as secondary batteries, it is desired to increase the capacity and rapid charge / discharge characteristics of materials used as electrodes.

  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 a problem, a positive electrode is formed using a conductive polymer having a polymer anion such as polyvinyl sulfonic acid as a dopant, lithium metal is used as a negative electrode, a cation transfer type, and thus an electrolytic solution is used. There has also been proposed a secondary battery that does not require a large amount and that does not substantially change the ion concentration in the electrolytic solution (see Patent Document 2). Recently, a secondary battery produced by using a positive electrode containing a conductive polymer and a polycarboxylic acid and a negative electrode made of a material capable of inserting and removing base metal or base metal ions has also been proposed (Patent Document). 3).

Japanese Patent Laid-Open No. 3-129679 Japanese Patent Laid-Open No. 1-132052 International Publication WO2013 / 002415

  However, the performance of the secondary battery of Patent Document 2 is not yet sufficient, and the secondary battery of Patent Document 3 also has room for further improvement of charge / discharge efficiency.

  The present invention has been made in view of the above-described circumstances, and its object is to provide conductive polymer particles having excellent charge / discharge efficiency, a method for producing the same, a positive electrode for an electricity storage device using the same, and a method for producing the same. To do.

  The inventors of the present invention have made extensive studies in order to obtain a high-performance power storage device with excellent charge / discharge efficiency. In this process, the conductive polymer particles generally have low conductivity on the particle surface, and secondary batteries using the conductive polymer tend to have a difficulty in obtaining sufficient charge / discharge efficiency. We focused further on further improvements. In order to improve the surface conductivity, it is conceivable to add a large amount of a conductive assistant. Increasing the content of the conductive assistant relative to the conductive polymer increases the charge / discharge efficiency, but the desired charge / discharge efficiency is improved. If it is intended to obtain, it becomes difficult to knead the electrode material. Further, when the content of the conductive auxiliary agent is increased, the weight other than the active material is increased, so that the capacity of the active material per positive electrode is reduced and the cost is increased. Therefore, as a result of further experiments, the present inventors came to recall that the surface of the conductive polymer particles was modified by proton acid treatment, and the particle surfaces were modified by being immersed in a solution containing a proton acid. It has been found that when conductive polymer particles are used, a high-performance power storage device having excellent charge / discharge efficiency can be obtained, and the present invention has been achieved.

  That is, the first gist of the present invention is a conductive polymer particle whose particle surface is modified by a proton acid treatment.

  Further, the present invention is a method for producing conductive polymer particles according to the first aspect, wherein the method comprises the step of immersing the conductive polymer particles before modification in a protonic acid-containing solution. Is the second gist. Furthermore, let the positive electrode for electrical storage devices produced using this conductive polymer particle be a 3rd summary. And the manufacturing method of the positive electrode for electrical storage devices provided with the process of forming an electrode layer using the said conductive polymer particle on a collector is made into the 4th summary.

  Thus, since the conductive polymer particle surface of the conductive polymer particle of the present invention is modified by proton acid treatment, the power storage device positive electrode containing the conductive polymer particle and the power storage device using the same have high charge / discharge efficiency. Will have.

  When the ratio of the proton acid treatment to the particles is 0.01 to 0.5 in terms of molar ratio, the electricity storage device positive electrode containing the particles and the electricity storage device using the same have high charge / discharge efficiency. .

  When the conductive polymer is polyaniline or a polyaniline derivative, the obtained electricity storage device has a higher capacity density.

  Further, the method for producing the conductive polymer particles, comprising the step of immersing the conductive polymer particles before modification in a protonic acid-containing solution, the particle surface can be sufficiently protonic acid treatment, The obtained electricity storage device has high charge / discharge efficiency.

It is sectional drawing which shows an example of the electrical storage device of this invention. It is a graph which shows the relationship between charging / discharging efficiency (%) of Examples 1-3 and the comparative example 1, and a surface modification ratio. It is a graph which shows the relationship between the charging / discharging efficiency (%) of Examples 4 and 5 and Comparative Example 1 and the surface modification ratio.

  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 electroconductive polymer particle of this invention is one of the positive electrode formation materials used for the positive electrode for electrical storage devices. The conductive polymer particle is characterized in that the particle surface is modified by proton acid treatment.

The conductive polymer particles of the present invention are, for example, as shown in FIG. 1, a material for forming a positive electrode 2 of an electricity storage device having an electrolyte layer 3 and a positive electrode 2 and a negative electrode 4 provided to face each other. Used as In FIG. 1, 1 is a positive electrode current collector, and 5 is a negative electrode current collector.
Hereinafter, the positive electrode 2, the negative electrode 4, and the electrolyte layer 3 will be described in order.

<Positive electrode>
The positive electrode 2 uses a positive electrode forming material containing conductive polymer particles whose particle surfaces are modified by proton acid treatment.

[Conductive polymer]
Here, the conductive polymer of the present invention will be described. The conductive polymer is formed by inserting or leaving an ionic species from the polymer 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 include, for example, 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. In addition, as another conductive polymer preferable in the present invention, a polymer in a dedope state obtained by dedoping the conductive polymer can be given.

  Specific examples of the conductive polymer include polyacetylene, polypyrrole, polyaniline, polythiophene, polyfuran, polyselenophene, polyisothianaphthene, polyphenylene sulfide, polyphenylene oxide, polyazulene, poly (3,4-ethylenedioxythiophene), These substituted polymers are exemplified. Of these, polyaniline and polyaniline derivatives are preferably used because of their large electrochemical capacity.

  In the present invention, the polyaniline is a polymer obtained by electrolytic polymerization or chemical oxidative polymerization of aniline, and the polyaniline derivative is, for example, a polymer obtained by electrolytic polymerization or chemical oxidative polymerization of a derivative of aniline. Say.

  Here, as the derivative of aniline, at least 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, and an alkoxyalkyl group is provided at a position other than the 4-position of aniline. What has 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, Examples include m-substituted anilines such as m-methoxyaniline, m-ethoxyaniline, m-phenylaniline. 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”.

(Preparation of conductive polymer)
In the present invention, the conductive polyaniline can be obtained by electrolytic polymerization of aniline in the presence of a protonic acid or chemical oxidative polymerization using an oxidizing agent in an appropriate solvent, as is well known. However, it can be preferably obtained by oxidative polymerization of aniline with an oxidizing agent in the presence of a protonic acid in an appropriate solvent. As the solvent, water is usually used, but a mixed solvent of a water-soluble organic solvent and water or a mixed solvent of water and a nonpolar organic solvent is also used. In this case, a surfactant or the like may be used in combination.

  For example, the oxidative polymerization of aniline using water as a solvent will be described in more detail. The chemical oxidative polymerization of aniline is performed in water using a chemical oxidant in the presence of a protonic acid. The chemical oxidant used may be either water-soluble or water-insoluble.

  Preferred examples of the oxidizing agent include ammonium peroxodisulfate, hydrogen peroxide, potassium dichromate, potassium permanganate, sodium chlorate, cerium ammonium nitrate, sodium iodate, and iron chloride.

  The amount of oxidant used for the oxidative polymerization of aniline is related to the yield of conductive polyaniline produced, and in order to quantitatively react the aniline used, the number of moles of aniline used (2.5 / n) It is preferable to use a double mole of oxidizing agent. However, n represents the number of electrons required when one molecule of the oxidizing agent itself is reduced. Therefore, for example, in the case of ammonium peroxodisulfate, n is 2 as understood from the following reaction formula.

(NH ₄ ) ₂ S ₂ O ₈ + 2e ⇒ 2NH ₄ ⁺ + 2SO ₄ ²⁻

  However, in order to suppress the polyaniline from becoming a peroxidized state, it is slightly less than (2.5 / n) times the number of moles of aniline to be used (2.5 / n). ) A ratio of 30 to 80% may be used with respect to the molar amount.

  In the production of the conductive polyaniline, the proton acid is doped with the produced polyaniline to make it conductive, and the aniline is salted in water and dissolved in water. The pH of the polymerization reaction system is preferably 1 or less. Used to maintain strong acidity. Accordingly, in the production of the conductive polyaniline, the amount of the protonic acid used is not particularly limited as long as the above object can be achieved, but usually 1.1 to 5 times the number of moles of aniline. Used in a range. However, when the amount of the protonic acid used is too large, the cost for waste liquid treatment is unnecessarily increased in the post-treatment of the aniline oxidative polymerization, so that it is preferably used in the range of 1.1 to 2 moles. It is done. Thus, as the protonic acid, those having strong acidity are preferable, and more preferable is a protonic acid having an acid dissociation constant pKa value of less than 3.0.

  Examples of such protic acids having an acid dissociation constant pKa value of less than 3.0 include sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, tetrafluoroboric acid, hexafluorophosphoric acid, hydrofluoric acid, hydroiodic acid, and the like. Inorganic acids, aromatic sulfonic acids such as benzenesulfonic acid and p-toluenesulfonic acid, and aliphatic sulfonic acids (or alkanesulfonic acids) such as methanesulfonic acid and ethanesulfonic acid are preferably used. A polymer having a sulfonic acid group in the molecule, that is, a polymer sulfonic acid can also be used. Examples of such polymer sulfonic acid include polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, poly (acrylamide-t-butyl sulfonic acid), phenol sulfonic acid novolak resin, and Nafion (registered trademark). Examples thereof include perfluorosulfonic acid. In the present invention, polyvinyl sulfate can also be used as a protonic acid.

  However, in addition to the above, for example, certain phenols such as picric acid, certain aromatic carboxylic acids such as m-nitrobenzoic acid, certain fats such as dichloroacetic acid, malonic acid, etc. Since the group carboxylic acid also has an acid dissociation constant pKa value of less than 3.0, it is used as a protonic acid in the production of conductive polyaniline.

  Among the various protic acids described above, tetrafluoroboric acid and hexafluorophosphoric acid are protonic acids containing the same anionic species as the base metal salt of the electrolyte salt of the nonaqueous electrolyte solution in the nonaqueous electrolyte secondary battery, For example, in the case of a lithium secondary battery, since it is a protonic acid containing the same anionic species as the lithium salt of the electrolyte salt of the non-aqueous electrolyte in the lithium secondary battery, it is preferably used.

  Note that, as described above, the protonic acid used in the production of the conductive polyaniline and the protonic acid used to modify the surface of the conductive polymer particles after the production of the conductive polymer may be the same or different. However, they are used in different steps.

  In addition, conductive polypyrrole can be obtained by using a suitable chemical oxidizing agent in an aqueous solution of pyrrole containing an organic sulfonate such as sodium alkylbenzene sulfonate such as sodium dodecylbenzene sulfonate or sodium anthraquinone sulfonate. Is obtained as a thin film on the anode by electrolytic oxidation polymerization of pyrrole using a stainless steel electrode in an aqueous solution of pyrrole containing sodium alkylbenzenesulfonate or organic sulfonate. be able to. In such a production method, sodium alkylbenzene sulfonate or organic sulfonate acts as an electrolyte, and the alkylbenzene sulfonate anion or organic sulfonate anion functions as a dopant for the generated polypyrrole to impart conductivity to polypyrrole. To do.

  In the present invention, the conductive polymer may be a polymer doped with a proton acid anion, and the dedope obtained by dedoping the polymer doped with the proton acid anion as described above. It may be a polymer in the state. If necessary, the dedoped polymer may be further reduced.

  Examples of a method for dedoping a conductive polymer include a method of neutralizing a conductive polymer doped with a proton acid anion with an alkali. For example, the conductive polymer doped with protonic acid anions is neutralized with alkali to be dedoped, and the resulting depolymerization is performed. A method of reducing the doped polymer with a reducing agent can be mentioned.

  When the conductive polymer doped with the proton acid anion is neutralized with an alkali, for example, the conductive polymer is put into an alkaline aqueous solution such as an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, or aqueous ammonia, What is necessary is just to stir under room temperature or under the heating of about 50-80 degreeC as needed. By conducting the alkali treatment under heating, the dedoping reaction of the conductive polymer can be promoted and dedoping can be performed in a short time.

  On the other hand, as described above, in order to reduce the dedoped polymer, the dedoped polymer is reduced to hydrazine monohydrate aqueous solution, phenylhydrazine / alcohol solution, sodium dithionite aqueous solution, sodium sulfite aqueous solution or the like. What is necessary is just to throw in in an agent solution and to stir under room temperature or the heating of about 50-80 degreeC as needed.

  Since the conductive polymer particle of the present invention has its particle surface modified by proton acid treatment, the proton acid used for surface modification will be described next.

[Protonic acid for particle surface modification]
The protonic acid for modifying the surface of the conductive polymer particles (hereinafter sometimes referred to as “particle surface modifying protonic acid”) is the same as the protonic acid used in the production of the conductive polyaniline described above. And may be the same as or different from the protonic acid containing the same anionic species as the electrolyte salt constituting the electrolyte layer of the electricity storage device described later. Among these, it is preferable to use a protonic acid containing the same anionic species as the electrolyte salt. Specifically, the proton acid for particle surface modification is as follows.

  The proton acid for particle surface modification is not necessarily required to be a strong acid because it is sufficient to modify only the particle surface, and a desired dope rate can be obtained if the concentration is high even with a weak acid.

  Examples of such protonic acids include weak acids such as phosphoric acid, halogen oxoacids, carbonic acid, sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, tetrafluoroboric acid, hexafluorophosphoric acid, hydrofluoric acid, and hydroiodic acid. Inorganic acids such as benzene sulfonic acid, aromatic sulfonic acid such as 10-camphor sulfonic acid, p-toluene sulfonic acid, and aliphatic sulfonic acid (or alkane sulfonic acid) such as methane sulfonic acid and ethane sulfonic acid. . Of these, weak acids such as phosphoric acid, halogen oxo acids, and carbonic acids are preferably used.

The particle surface modifying protonic acid is preferably used in a liquid form so that the surface of the conductive polymer particles can easily come into contact with the protonic acid, and is preferably diluted with a solvent and used as a protonic acid solution. The concentration of the protonic acid solution varies depending on the acid dissociation constant, but in the case of a strong acid, it is preferably 0.01 to 0.2 mol / dm ³ . In addition, as the solvent, for example, at least one nonaqueous 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.

  Further, the amount of the proton acid for modifying the particle surface is not particularly limited as long as it can modify the surface of the conductive polymer particles. However, when the conductive polymer is polyaniline, Is used in a range of 0.01 to 0.5 times the number of moles of aniline. However, when the amount of the protonic acid used is too large, the cost for waste liquid treatment is unnecessarily increased in the post-treatment of aniline oxidative polymerization. It is used in the range of 0.01 to 0.15 moles.

[Conductive polymer particles with modified surface]
Using the conductive polymer and the protonic acid for particle surface modification, the surface of the conductive polymer particle is modified with ptronic acid dope so that the surface of the present invention is modified (hereinafter referred to as “surface”). Sometimes referred to as “modified conductive polymer particles”).

  The size of the surface-modified conductive polymer particles of the present invention thus obtained is preferably a median diameter of 0.001 to 1000 μm, more preferably 0.01 to 100 μm, and particularly preferably 0.00. 1-20 μm. The median diameter can be measured using, for example, a static light scattering particle size distribution measuring apparatus.

  The size of the conductive polymer particles before the surface modification is substantially the same as the size of the conductive polymer particles after the surface modification.

  As a method for modifying the surface of the conductive polymer, for example, a method of preparing the above protonic acid solution, immersing the conductive polymer particles in the solution, and modifying the surface of the conductive polymer particles by proton acid treatment, Other examples include a method of putting conductive polymer particles in a vaporized proton acid atmosphere and treating the particle surface with a proton acid, and so on. Since surface conductivity is obtained, it is preferable.

  In addition, the conductive polymer particles to be subjected to the immersion treatment may be in a powder form or may be in a state of constituting an electrode.

  Further, the immersion treatment is preferably performed for a time sufficient for the protonic acid solution to modify the entire particle surface, and the particle surface is usually immersed for 5 to 20 hours at room temperature (25 ° C.). Reformed. In view of the balance between the work efficiency and the degree of modification, the immersion time is particularly preferably 10 to 15 hours.

  As described above, the proton acid used in the production of the conductive polyaniline and the proton acid for particle surface modification may be the same or different as components. The protonic acid used in the production of the conductive polyaniline is one in which the protonic acid aniline is inserted into and removed from the inside of the particle because the conductive polyaniline is prepared by electrolytic polymerization of aniline in the presence of the protonic acid. On the other hand, the proton acid for particle surface modification modifies the surface of the conductive polymer particles, and the proton acid aniline is inserted / desorbed only on the particle surface. By observing it, it can be determined whether or not the particle has been modified with the proton acid for particle surface modification.

  The ratio of the protonic acid treatment to the conductive polymer particles whose surface has been modified is preferably 0.01 to 0.5, more preferably 0.01 to 0.2, still more preferably 0 in terms of molar ratio. .01 to 0.15. In the process of proton acid treatment, it tends to be difficult to obtain the above upper limit or more, and when the ratio of proton acid treatment is too low, the capacity density of the electricity storage device tends to be excellent, and the charge / discharge efficiency and cycle characteristics tend to be inferior. .

  The ratio of the protonic acid treatment to the particles quantifies the number of moles of the conductive polymer, and then the number of moles of the dopant. By using the number of moles thus obtained, the ratio of the number of moles of the dopant to the number of moles of the conductive polymer is obtained, whereby the ratio of the proton acid treatment to the particles can be obtained.

  For example, when the conductive polymer is polyaniline, the amount of N element is quantified using a CHN element analyzer and the number of moles of polyaniline is calculated. Next, using an ICP apparatus, the amount of S element (sulfate ion), P element (phosphate ion), etc. with respect to the total amount of the modified conductive polymer particles is quantified, and the number of moles of the dopant is calculated. Using these mole numbers, the ratio of the proton acid treatment to the particles is determined.

  As the measurement and observation of the particle cross section, the particle morphology, the conduction path of the particle, etc. are observed by SEM (scanning electron microscope) observation, AFM (atomic force microscope) measurement, and SPM (scanning probe microscope) measurement. And so on. For example, in the observation of the cross section of the conductive polymer particle, it can be determined by the fact that the conductivity of the particle surface is increased without depending on the conductive auxiliary agent.

  In addition to the conductive polymer particles, a binder, a conductive assistant, water and the like can be appropriately added to the positive electrode forming material of the present invention as necessary.

  As the binder, for example, a binder such as vinylidene fluoride or styrene-butadiene rubber is used. In addition, a polyanion, an anion compound having a relatively large molecular weight, an anionic material having low solubility in the electrolytic solution, and the like can be used.

  Especially, it is preferable that the main component of a binder consists of the said anionic material. Here, the main component means a component that occupies the majority of the whole, and includes the case where the whole consists of only the main component.

  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. Polymethacrylic 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 ideal replacement rate for the lithium type is 100%, but this is not necessarily the case, and it is preferably 40% to 100%.

  When a polymer such as the above polycarboxylic acid is used as a binder, since this polymer also functions as a dopant, the electricity storage device according to the present invention has a rocking chair type mechanism and is involved in improving its characteristics. It seems to be.

  The binder is generally 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 binder is too small, there is a tendency that a uniform electrode cannot be obtained, and even if the amount of the binder is too large, the active material is reduced as a result, and an energy storage device having a high energy density cannot be obtained. is there.

  In addition, the conductive auxiliary that is appropriately added to the positive electrode forming material according to the present invention may be any conductive material that does not change its property depending on the potential applied during discharge of the electricity storage device. For example, conductive carbon In particular, conductive carbon black such as acetylene black and ketjen black, and fibrous carbon material such as carbon fiber and carbon nanotube are preferably used, and particularly preferably conductive carbon black. is there.

  The conductive assistant is preferably 1 to 30 parts by weight, more preferably 4 to 20 parts by weight, and particularly preferably 1 to 15 parts by weight with respect to 100 parts by weight of the conductive polymer. . Since the conductive polymer particles of the present invention themselves exhibit conductivity, the amount of the conductive auxiliary agent tends to be reduced as compared with the case of using particles that are not surface-modified.

  The positive electrode 2 for an electricity storage device of the present invention is preferably composed of a composite of the conductive polymer particles and an optional component such as an anionic material added as necessary, and is usually formed on a porous sheet. .

  The thickness of the positive electrode 2 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 2 is obtained by subtracting the thickness of the positive electrode 2 and calculating.

  The positive electrode 2 for an electricity storage device of the present invention is formed as follows, for example. A conductive additive, a binder, and water are added to the conductive polymer particles and sufficiently dispersed to prepare a 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.

  Thereby, the positive electrode for electrical storage devices which expresses high charging / discharging efficiency is obtained. The reason why such a high charge / discharge efficiency is manifested is not necessarily clear, but it is considered that the charge / discharge reaction occurs smoothly due to the improved conductivity of the particle surface due to the modification of the particle surface.

<Negative electrode>
The negative electrode 4 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 4 preferably conforms to the thickness of the positive electrode 2.

<Electrolyte layer>
The electrolyte layer 3 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."

  And, as the above-mentioned various additives, operation such as electrode surface control agents such as vinylene carbonate, overcharge preventing agents such as biphenyl, cyclohexylbenzene and anisole fluoride, flame retardants such as phosphate esters and phosphazenes, etc. The one that comprehensively secures voltage, charge / discharge speed, safety, life characteristics, and the like.

  In addition to the positive electrode 2, the electrolyte layer 3, and the negative electrode 4, the electricity storage device uses a separator. Such a separator can be used in various modes. For example, an insulating porous sheet that can prevent an electrical short circuit between the positive electrode 2 and the negative electrode 4, is electrochemically stable, has high ion permeability, and has a certain mechanical strength is used. For example, a porous sheet made of a resin such as paper, nonwoven fabric, polypropylene, polyethylene, or polyimide is preferably used. These may be used alone or in combination of two or more. Moreover, as above-mentioned, when the electrolyte layer 3 is a sheet | seat which consists of solid electrolytes, since it itself serves as a separator, it is not necessary to prepare another separator separately.

  As the current collectors 1 and 5 in FIG. 1, those having characteristics such as excellent electronic conductivity, volume reduction inside the battery (thinning), and easy processing can be used. Examples of those satisfying such characteristics include metal foils and meshes such as nickel, aluminum, stainless steel, and copper. The positive electrode current collector (for example, current collector 1) and the negative electrode current collector (for example, current collector 5) may be made 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 2 and the negative electrode 4 to produce a laminate, and this 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 ultrahigh purity argon gas.

  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 added to the tetrafluoroboric acid aqueous solution, the aniline was dispersed as oily droplets in the tetrafluoroboric acid aqueous solution, but then dissolved in water within a few minutes, and the uniform and transparent aniline 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 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. Suction filtration was performed with two filter papers (manufactured by ADVANTEC) to obtain a powder. 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 above 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 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 method conductivity measurement by the Van der Pau 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 electric conductivity of the disk measured by the 4-terminal conductivity measurement by the Van der Pau 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 binder solution>
Polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 1 million) was dissolved in water to obtain 20.5 g of a 4.4 wt% concentration uniform and viscous polyacrylic acid aqueous solution. To this polyacrylic acid aqueous solution, 0.15 g of lithium hydroxide was added and dissolved again to prepare a polyacrylic acid-polylithium acrylate complex solution (binder solution) in which 50% of the acrylic acid sites were replaced 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 (manufactured by 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 lithium hexafluorophosphate (LiPF ₆ ) having a concentration of 1 mol / dm ³ 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.

  Using the prepared material, first, proton acid-treated particles, which are materials for producing a positive electrode, were produced.

<Preparation of proton acid-treated particles>
The polyaniline particles 5 g in the dedope state were each prepared with 200 ml of a solution of the protonic acid and acid concentration shown in Table 1 below, and the polyaniline particles were immersed in the solution and allowed to stand at 60 ° C. for 15 hours. . Thereafter, the mixture was suction filtered, washed with methanol and acetone, and then dried in a vacuum dryer at 40 ° C. for 15 hours to prepare surface-modified particles 1 to 5.

Next, the CHN element analysis and the ICP analysis were performed on the particles 1 to 5, respectively, using a CHN element analyzer (ELEMENTAR, varioEL III) and an ICP analyzer (Hitachi High-Tech Science, SPS-3520). The ratio of the protonic acid to the polyaniline particles was determined, and the surface modification ratio is shown in Table 1 below.
For comparison, the undoped polyaniline particles not subjected to proton acid treatment are also shown in Table 1 below as particles 6.

[Example 1]
<Production of positive electrode>
After mixing 1 g of the powder of the particles 1 shown in Table 1 above with 0.24 g of conductive carbon black (Denka Black, Denka Black) and 1 g of water, this is mixed with the polyacrylic acid-lithium lithium acrylate composite. In addition to 4.08 g of the body solution, kneaded well with a spatula, and then subjected to ultrasonic treatment with an ultrasonic homogenizer for 5 minutes to obtain a paste having fluidity. This paste was subjected to a defoaming operation for 3 minutes with Awatori Nertaro (manufactured by Shinky Corporation) to prepare a positive electrode forming paste 1.

  The paste obtained above was adjusted to a solution coating thickness of 360 μm by using a desktop automatic coating apparatus (manufactured by Tester Sangyo Co., Ltd.) and a doctor blade type applicator with a micrometer, and a coating speed of 10 mm / second. Then, it was coated on an etching aluminum foil for electric double layer capacitor (manufactured by Hosen Co., Ltd., 30CB). Next, after leaving at room temperature (25 ° C.) for 45 minutes, it was dried on a hot plate having a temperature of 100 ° C. to produce a polyaniline sheet electrode (positive electrode).

  The prepared positive electrode, prepared negative electrode, and separator were all placed in a glove box immediately after being dried at 100 ° C. for 5 hours with a vacuum dryer before assembling the battery.

<Manufacture of secondary batteries>
And it combined so that a negative electrode and a positive electrode might not contact in order of a negative electrode, a separator, and a positive electrode, it pinched | interposed with the aluminum laminate film, and it heat-sealed. After adding the electrolytic solution, it was sealed by heat sealing to produce a laminated cell lithium secondary battery.

[Example 2]
1 g of the powder of the particles 2 shown in Table 1 above was mixed with 0.25 g of conductive carbon black (Denka Black, Denka Black) and 1 g of water, and then mixed with the polyacrylic acid-polylithium acrylate composite. In addition to 4.30 g of the body solution, kneaded well with a spatula, and then subjected to ultrasonic treatment for 5 minutes with an ultrasonic homogenizer to obtain a paste having fluidity. This paste was defoamed for 3 minutes with Awatori Nertaro (Sinky Corp.) to prepare positive electrode forming paste 2.

  A lithium secondary battery was produced in the same manner as in Example 1, except that the positive electrode forming paste 1 was replaced with the prepared positive electrode forming paste 2 in Example 1.

Example 3
After mixing 1 g of the powder 3 of the particles 3 shown in Table 1 above with 0.25 g of conductive carbon black (Denka Black, Denka Black) and 1 g of water, this is mixed with the polyacrylic acid-lithium lithium acrylate composite. In addition to 4.51 g of the body solution, kneaded well with a spatula, and then subjected to ultrasonic treatment for 5 minutes with an ultrasonic homogenizer to obtain a paste having fluidity. This paste was subjected to a defoaming operation for 3 minutes with Awatori Nertaro (Sinky Corp.) to prepare a positive electrode forming paste 3.

  A lithium secondary battery was produced in the same manner as in Example 1, except that the positive electrode forming paste 1 was replaced with the prepared positive electrode forming paste 3 in Example 1.

Example 4
After mixing 1 g of powder 4 of the particles 4 shown in Table 1 above with 0.26 g of conductive carbon black (Denka Black, Denki Kagaku Kogyo Co., Ltd.) and 1 g of water, this is mixed with the polyacrylic acid-polylithium acrylate composite. After adding to body solution 4.73g and kneading well with a spatula, the paste which has fluidity | liquidity was obtained by performing ultrasonic treatment for 5 minutes with an ultrasonic homogenizer. This paste was subjected to a defoaming operation for 3 minutes with Awatori Nertaro (manufactured by Shinky Corporation) to prepare a positive electrode forming paste 4.

  A lithium secondary battery was produced in the same manner as in Example 1, except that the positive electrode forming paste 1 was replaced with the prepared positive electrode forming paste 4 in Example 1.

Example 5
1 g of the powder of particles 5 shown in Table 1 above was mixed with 0.26 g of conductive carbon black (Denka Black, Denka Black) and 1 g of water, and then mixed with the polyacrylic acid-lithium lithium acrylate composite. In addition to 4.95 g of the body solution, kneaded well with a spatula, and then subjected to ultrasonic treatment with an ultrasonic homogenizer for 5 minutes to obtain a paste having fluidity. This paste was subjected to defoaming operation for 3 minutes with Awatori Nertaro (manufactured by Shinky Corporation) to prepare positive electrode forming paste 5.

  A lithium secondary battery was produced in the same manner as in Example 1, except that the positive electrode forming paste 1 was replaced with the prepared positive electrode forming paste 5 in Example 1.

[Comparative Example 1]
After mixing 1 g of powder 6 of the particles 6 shown in Table 1 above with 0.26 g of conductive carbon black (Denka Black, Denki Kagaku Kogyo Co., Ltd.) and 1 g of water, this was mixed with the polyacrylic acid-lithium lithium acrylate composite. In addition to 4.98 g of the body solution, kneaded well with a spatula, and then subjected to ultrasonic treatment for 5 minutes with an ultrasonic homogenizer to obtain a paste having fluidity. This paste was subjected to a defoaming operation for 3 minutes with Awatori Nertaro (manufactured by Shinky Corporation) to prepare a positive electrode forming paste 6.

  A lithium secondary battery was fabricated in the same manner as in Example 1, except that the positive electrode forming paste 1 was replaced with the prepared positive electrode forming paste 6 in Example 1.

  In the above examples and comparative examples, the amount of conductive polymer per gram of particle varies depending on the difference in the particle surface modification ratio. Therefore, in order to make the amount of the conductive polymer per gram of the particles uniform, the addition rate of the binder and the conductive auxiliary agent is changed depending on the particles used.

(Measurement of charge / discharge efficiency)
Each power storage device obtained as described above has a capacity in a constant current-constant voltage charge / constant current discharge mode in a 25 ° C. environment using a battery charging / discharging device (Hokuto Denko, SD8). Density measurements were made. The end-of-charge voltage is 3.8 V. After the voltage reaches 3.8 V due to constant current charging of 0.1 mA, a constant-voltage charge of 3.8 V is performed for 2 minutes, and then the end-of-discharge voltage reaches 2.0 V. A constant current discharge was performed. This was set as 1 cycle, charging / discharging was repeated, charge capacity and discharge capacity were investigated, and the value which remove | divided discharge capacity by charge capacity was computed as charging / discharging efficiency.

  In Examples 1 to 3 using sulfuric acid as a protonic acid and Comparative Example 1 without a protonic acid treatment, the results of charge and discharge efficiency after 25 cycles in the above charge and discharge device are shown in Table 2 below. This is shown in the graph of 2.

  Tables 3 and 3 show the results of charge and discharge efficiency after 7 cycles in Examples 4 and 5 using phosphoric acid as the proton acid and Comparative Example 1 without the proton acid treatment in the above charge / discharge device. Together with the graph of FIG.

  From the results of Tables 1 to 3 and FIGS. 2 and 3, in Examples using positive electrodes containing conductive polymer particles whose particle surface was modified by proton acid treatment, Comparative Example in which the particle surface was not modified Compared to 1, it was found that the charge / discharge efficiency (%) was improved.

  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.

1 Current collector (for positive electrode)
2 Positive electrode 3 Electrolyte layer 4 Negative electrode 5 Current collector (for negative electrode)

Claims (7)

  Conductive polymer particles, wherein the particle surfaces are modified by proton acid treatment.   The conductive polymer particles according to claim 1, wherein the modification by the proton acid treatment is performed by immersion in a proton acid-containing solution.   3. The conductive polymer particle according to claim 1, wherein a ratio of the proton acid treatment to the particle is 0.01 to 0.5 in terms of molar ratio.   The conductive polymer particle according to any one of claims 1 to 3, wherein the conductive polymer is polyaniline or a polyaniline derivative.   A method for producing the conductive polymer particles according to any one of claims 1 to 4, comprising a step of immersing the conductive polymer particles before modification in a protonic acid-containing solution. Method for producing conductive polymer particles.   The positive electrode for electrical storage devices using the conductive polymer particle as described in any one of Claims 1-4, or the conductive polymer particle obtained by the manufacturing method of Claim 5.   The process of forming an electrode layer on the electrical power collector using the conductive polymer particle as described in any one of Claims 1-4 or the conductive polymer particle obtained by the manufacturing method of Claim 5 is provided. A method for producing a positive electrode for an electricity storage device.

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