JP2007119386A - Method for purifying indole derivative trimer, electrode active substance containing formed trimer, method for producing electrode active substance and electrochemical cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily removing metal impurities from an indole derivative trimer containing the metal impurities. <P>SOLUTION: An indole derivative trimer containing metal impurities is mixed with an imidazole compound in a solvent containing water under heating. The indole derivative trimer from which the metal impurities are removed is separated from the obtained mixture by filtration. The indole derivative trimer containing metal impurities is mixed with a protonic acid to simultaneously carry out doping of the indole derivative trimer and removal of metal impurities. The electrode active substance of an electrochemical cell comprises the indole derivative trimer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a trimer of an indole derivative used as an electrode active material of an electrochemical cell such as a secondary battery, an electric double layer capacitor, a redox capacitor, or a capacitor. The present invention relates to a purification method to be removed. The present invention also relates to a method for producing an electrode active material in which doping of an indole derivative trimer and removal of contained transition metal impurities are simultaneously performed. The present invention also relates to an electrode active material containing a high purity indole derivative trimer produced by such a method, and further relates to an electrochemical cell using this electrode active material.

  Indole compounds are known to be used as electrode materials for electrochemical cells in which protons can act as charge carriers, and indole derivative trimers are known as useful electrode active materials. Patent Document 1 discloses that among indole derivatives, a trimer of an indole carboxylic acid ester can be an electrode active material having sufficient electromotive force and capacity and excellent cycle characteristics. As a method for producing such an indole derivative trimer, an electrolytic polymerization method as disclosed in Non-Patent Document 1 and a chemical polymerization method as disclosed in Patent Document 2 are known.

  Non-Patent Document 1 reports a synthesis of a trimer by electrolytic reaction of unsubstituted indole and 5-cyanoindole. The indole derivative trimer obtained by the method according to Non-Patent Document 1 does not use an oxidizing agent, so a high-purity product is obtained. However, it is difficult to produce in large quantities, and as an industrial production method The problem remains that is difficult to apply.

  On the other hand, the method described in Patent Document 2 relates to a production method including dropping and reacting a solution containing at least one oxidant, at least one organic solvent and water in a solution containing an indole derivative. .

  The method described in this patent document is a method capable of industrially producing a target indole derivative trimer in large quantities. However, since metal compounds such as ferric chloride and cupric chloride are used as the oxidizing agent, the resulting indole derivative trimer inevitably contains metal components, halogen components, etc. derived from the oxidizing agent in the polymerization process. To do.

  In order to use the produced indole derivative trimer as an electrode active material, a dopant anion is doped. The doping process of the indole derivative trimer is generally performed in a solution containing a dopant anion such as dilute sulfuric acid at room temperature. At this stage, although the contained impurities are slightly reduced, it cannot be said that the impurities are sufficiently removed. When an indole derivative trimer containing a metal impurity as an impurity is applied to an electrochemical cell as an electrode active material, it causes an increase in leakage current due to a side reaction of the impurity. Therefore, it is desirable to remove contained impurities, particularly metal impurities as much as possible.

  In general, as a method for removing metal impurities, a method of eluting metal impurities by treatment with strong acid such as concentrated sulfuric acid or concentrated hydrochloric acid is known. Treatment with a strong acid is not preferable because it causes a decrease in performance as an electrode active material.

  Patent Document 3 proposes the use of a ligand compound that forms a metal complex instead of removing metal impurities with an acid. The nanoscale carbon tube or the nanoscale carbon tube enclosing the transition metal or its alloy in the inner space of the tube and the carbonaceous material containing the transition metal impurities in this method are used for acid treatment. Even the transition metal partially encapsulated in the inner space part of the tube or its alloy is eluted, and the problem is to modify the nanoscale carbon tube that encapsulates the transition metal or its alloy in the inner space part of the tube, A method that does not use an acid is proposed.

However, the indole derivative trimer targeted by the present invention is an organic compound having a nitrogen atom, and it is not known at all whether metal impurities can be removed by the method described in Patent Document 3. Further, as described above, if the doping treatment with an acid such as dilute sulfuric acid can be performed simultaneously with the removal of impurities, it is extremely advantageous industrially.
J. Chem. Soc., Faraday Trans., 93 (1997), 3791p JP 2005-187893 A WO2002 / 032903 Specification JP 2005-154225 A

  The objective of this invention is providing the purification method which can remove a metal impurity easily from the indole derivative trimer containing a metal impurity. Another object of the present invention is to provide a method for producing an electrode active material containing a high-purity indole derivative trimer, which can simultaneously perform doping of an indole derivative trimer and removal of contained metal impurities.

  Furthermore, in the present invention, by using an electrode active material that has been able to sufficiently remove such metal impurities, an electrochemical cell such as a secondary battery, an electric double layer capacitor, a redox capacitor, or a capacitor has a leakage current. It aims at providing the electrochemical cell excellent in the characteristic.

  As a result of intensive studies to solve the above problems, the present inventors mixed an indole derivative trimer containing a metal impurity with an imidazole compound under heating in a solvent containing water to form a metal complex. It was found that metal impurities can be easily removed from the indole derivative trimer simply by filtering and separating the liquid component containing the metal complex and the indole derivative trimer from which the metal impurity has been removed. In addition, it has been found that doping can be simultaneously performed by using a protonic acid in combination, and the present invention has been completed.

  That is, the present invention relates to a method for purifying an indole derivative trimer that removes a metal impurity from an indole derivative trimer containing a metal impurity, the indole derivative trimer represented by the following general formula (1) containing a metal impurity. Mixing a body with an imidazole compound that forms a complex with a metal impurity under heating in a solvent containing at least water, and separating the indole derivative trimer from which the metal impurity has been removed from the resulting mixture. The present invention relates to a purification method characterized by

(In the formula, each R is independently a hydrogen atom, hydroxyl group, carboxyl group, nitro group, vinyl group, halogen atom, acyl group, cyano group, amino group, trifluoromethyl group, sulfonyl group, sulfonic acid group, Represents a trifluoromethylthio group, a carboxylic acid ester group, a sulfonic acid ester group, an alkoxyl group, an alkylthio group, an aryloxy group, an arylthio group, an alkyl group, an aryl group, or a heterocyclic compound residue.)

  The present invention also relates to a method for producing an electrode active material for an electrochemical cell, which contains an electrolyte containing a proton source and can operate so that protons act as charge carriers in an oxidation-reduction reaction associated with charge and discharge. The indole derivative trimer represented by the general formula (1) containing impurities is mixed with an aqueous solution of a protonic acid containing an anion of the same chemical species as the electrolyte used in the electrochemical cell under heating, and / or At the same time, the method comprises a step of mixing an imidazole compound that forms a metal complex with a metal impurity, and separating the indole derivative trimer doped with a proton acid anion from which the metal impurity is removed. The present invention relates to a method for producing an electrode active material.

  Furthermore, the present invention relates to an electrode active material obtained by the above production method and containing an indole derivative trimer, preferably with a purity of 95% or more.

  In addition, the present invention is an electrochemical cell containing an electrolyte containing a proton source and capable of operating so that protons act as charge carriers in an oxidation-reduction reaction associated with charge and discharge, and at least the electrode described above as an electrode active material The present invention relates to an electrochemical cell containing an active material.

  According to the present invention, metal impurities can be efficiently and easily removed from an indole derivative trimer containing metal impurities.

  Moreover, by mixing the protonic acid, removal of metal impurities and doping can be performed at the same time, and when used as an electrode active material, an electrochemical cell having excellent leakage current characteristics can be provided.

  The indole derivative trimer to which the present invention is applied is produced by a method using a transition metal compound as an oxidizing agent as described in Patent Document 2, and is represented by the following general formula (1). .

(In the formula, each R is independently a hydrogen atom, hydroxyl group, carboxyl group, nitro group, vinyl group, halogen atom, acyl group, cyano group, amino group, trifluoromethyl group, sulfonyl group, sulfonic acid group, Represents a trifluoromethylthio group, a carboxylic acid ester group, a sulfonic acid ester group, an alkoxyl group, an alkylthio group, an aryloxy group, an arylthio group, an alkyl group, an aryl group, or a heterocyclic compound residue.)

  In the said General formula (1), C1-C20 acyl groups, such as a formyl group, an acetyl group, a propionyl group, are mentioned as an acyl group.

Carboxylic acid ester groups are represented by COOR ′, and similarly sulfonic acid ester groups are represented by SO ₃ R ′. Here, R ′ is a linear or branched alkyl group having 1 to 6 carbon atoms.

  Examples of the alkyl component in the alkyl group, alkoxyl group, and alkylthio group include the hydroxyl group, carboxyl group, nitro group, vinyl group, halogen atom, acyl group, cyano group, amino group, trifluoromethyl group, and sulfonyl exemplified as R. Group, sulfonic acid group, trifluoromethylthio group, carboxylic acid ester group, sulfonic acid ester group, alkoxyl group, alkylthio group, arylthio group, aryl group, heterocyclic group optionally having a substituent, A branched or cyclic alkyl group having 1 to 20 carbon atoms in total.

  The aryl component in the aryl group, aryloxy group, and arylthio group is an aryl group having 6 to 20 carbon atoms such as a phenyl group or a naphthyl group, and the substituents exemplified as R as a substituent, that is, a hydroxyl group , Carboxyl group, nitro group, vinyl group, halogen atom, acyl group, cyano group, amino group, trifluoromethyl group, sulfonyl group, sulfonic acid group, trifluoromethylthio group, carboxylic acid ester group, sulfonic acid ester group, alkoxyl A group, an alkylthio group, an arylthio group, an alkyl group, an aryl group, or a heterocyclic group.

  The heterocyclic group is a cyclic group containing nitrogen, oxygen, sulfur atoms, etc. as a heteroatom having 2 to 20 carbon atoms, such as furyl, thienyl, pyrrolyl, imidazolyl, triazolyl, oxazolyl, thiazolyl, pyridyl, indolyl, etc. Groups.

  Among them, an indole derivative trimer having at least one carboxylic acid ester group in each indole unit is preferable.

  The indole derivative trimer represented by the general formula (1) is obtained from a corresponding indole monomer represented by the following general formula (2), a chemical polymerization method using an oxidizing agent described in Patent Document 2, etc. Manufactured by.

（式中、Ｒは、各々独立に、一般式（１）におけるＲと同様の意味を示す。）

(In the formula, each R independently represents the same meaning as R in the general formula (1).)

  Examples of the oxidizing agent include ferric chloride hexahydrate, anhydrous ferric chloride, ferric nitrate nonahydrate, ferric nitrate, ferric sulfate n-hydrate, ferric sulfate ammonium Dihydrate, ferric perchlorate n hydrate, ferric tetrafluoroborate, cupric chloride, cupric sulfate, cupric tetrafluoroborate, tetrafluoroboronitrosonium, Ammonium persulfate, sodium persulfate, potassium persulfate, potassium periodate, hydrogen peroxide, ozone, potassium hexacyanoferric acid, tetraammonium cerium (IV) sulfate dihydrate, bromine, iodine and the like. Preferably ferric chloride hexahydrate, anhydrous ferric chloride, ferric nitrate nonahydrate, ferric nitrate, ferric sulfate n-hydrate, ferric sulfate ammonium dodecahydrate Iron compounds such as ferric perchlorate n-hydrate and ferric tetrafluoroborate. These oxidizing agents may be used alone or in combination of two or more. It can be used in combination in proportions.

  The indole derivative trimer thus produced contains several mass% of metal impurities as a metal. Therefore, an object of the present invention is to remove such metal impurities. The present invention also provides a method for performing a doping treatment necessary as an electrode active material simultaneously with removal of metal impurities. Hereinafter, the basic mechanism of the method of the present invention will be described.

1. By dispersing the indole derivative trimer in a solvent containing water (hereinafter referred to as an aqueous solvent) under heating, metal impurities contained in the indole derivative trimer are eluted in the aqueous solvent. At this time, by adding a protonic acid to the aqueous solvent, elution of metal impurities is promoted, and an indole derivative trimer can be doped with any protonic acid anion.

2. Next, / or simultaneously, by mixing the imidazole compound, the eluted metal impurity and the imidazole compound form a metal complex.

3. From this reaction solution, the indole derivative trimer and the metal complex dissolved in the reaction solvent are separated.

  Above 1. In an indole derivative trimer and an aqueous solvent, the temperature of the mixture of the indole derivative trimer and the aqueous solvent is added after heating the indole derivative trimer, so that the aggregated indole derivative trimer particles can be made more uniform. Can be dispersed. Moreover, uniform doping is performed by adding a protonic acid. Furthermore, since the permeability of the protonic acid to the indole derivative trimer particles is improved, the elution of the contained metal impurities is promoted, and even when a dilute acid such as dilute sulfuric acid is used, a sufficient metal impurity removal effect can be obtained. Can do. At this time, as the proton acid permeates, the particles expand, and impurities such as unreacted raw materials that are physically adsorbed on the particles are likely to be detached, so that the impurities can be more effectively removed. it can.

  Next, the above 2. As shown in FIG. 2, by adding an imidazole compound, nitrogen of imidazole coordinates with the eluted metal to form a complex. By complexing in this manner, reattachment of metal to the indole derivative trimer particles can be prevented, and the obtained complex can exist in a dissolved state in the solvent used. As shown in Fig. 4, it can be easily separated from the indole derivative trimer particles by a simple separation method such as filtration.

  In the present invention, a solvent containing water is used as the solvent. As a solvent that can be used with water, a dispersion state of the indole derivative trimer can be maintained, and a solvent compatible with water can be used. For example, alcohols and ketones can be used. As the solvent, it is preferable to use substantially only water.

  Protic acids include sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluorosilicic acid and other inorganic acids, saturated monocarboxylic acids, aliphatic carboxylic acids, oxycarboxylic acids, p-toluene Examples thereof include organic acids such as sulfonic acid, polyvinyl sulfonic acid, and lauric acid. Protic acid is preferably used as an aqueous solution having a concentration of 30% by mass or less. When a high concentration of protonic acid is used, the performance may be deteriorated due to structural deterioration of the indole derivative trimer. Further, heat treatment can be performed using only a solvent containing water without using a protonic acid.

  In order to perform doping necessary as an electrode active material simultaneously with the removal of metal impurities, a protonic acid containing an anion of the same chemical species as the electrolyte used in the electrochemical cell is used. In addition, doping can be performed separately. After doping in an aqueous solvent to which no proton acid is added, doping is performed by a conventional method, or after treatment in an aqueous solvent containing a proton acid and dedoping with an alkali or the like. And re-doping with a protonic acid containing a predetermined dopant anion. It may also be possible to use without prior doping.

  Examples of the imidazole compound that forms the metal complex include 2,2-biimidazole, 2- (2-pyridyl) imidazole, and 1H-imidazole. Among these, 1H-imidazole is preferable. These imidazole compounds are excellent in solubility in water and in coordination with metals, and both metal-complexed imidazole compounds and unreacted imidazole compounds are dissolved in an aqueous medium. It can be easily separated from the indole derivative trimer by filtration.

  Mixing of the indole derivative trimer with an aqueous solvent or an aqueous solvent containing a protonic acid is carried out under heating. The heating temperature is not particularly limited as long as it is in a temperature range below the decomposition temperature of the indole derivative trimer. When the indole derivative trimer is mixed with an aqueous solvent or an aqueous solvent containing a protonic acid and then heated, it is preferably heated at a temperature range of 80 ° C. or higher and lower than the reflux temperature of the mixture, preferably at the reflux temperature of the solvent. . In addition, when an indole derivative trimer is heated in advance and then an aqueous solvent or an aqueous solvent containing a protonic acid is added, the indole derivative trimer is heated to a temperature range of 100 to 300 ° C, preferably 180 to 270 ° C. After heating to a temperature range, a heated aqueous solvent or an aqueous solvent containing a protonic acid, preferably a boiling solvent is added. The heating and holding time is not particularly limited, but the treatment time is preferably set shorter as the temperature is closer to the decomposition temperature of the indole derivative trimer, and is preferably set as appropriate depending on the heating temperature. When heated for a long time in the vicinity of the decomposition temperature, the performance may be deteriorated due to structural deterioration.

  The mixing amount of the aqueous solvent or the aqueous solvent containing a protonic acid is not particularly limited as long as the indole derivative trimer is sufficiently wetted, but is usually 1 to 50 times the mass of the indole derivative trimer. , Preferably 5-30 mass times, more preferably 10-20 mass times.

  The addition / mixing of the next imidazole compound is also preferably carried out under heating. The mixing temperature is not particularly limited as long as it is in a temperature range below the boiling point of the imidazole compound. In addition, when an aqueous solvent or an aqueous solvent containing a protonic acid is added after heating the indole derivative trimer in advance, the imidazole compound may be added together with the aqueous solvent or the aqueous solvent containing a protonic acid.

  The amount of the imidazole compound used is not particularly limited as long as an amount capable of sufficiently reacting with the contained metal impurities is used. There is no problem even if an excessive amount of the imidazole compound is added. The treatment time after the addition of the imidazole compound may be a time sufficient for the complexing reaction between the contained metal impurity and the imidazole compound to proceed, and may be appropriately set according to the heating temperature condition and the amount of the imidazole compound added. .

  After being treated in this manner, the indole derivative trimer is separated from the reaction mixture by filtration. When performing filtration separation, in order to enhance the separation effect from the water-soluble metal complex or imidazole compound remaining in the indole derivative trimer, washing may be performed using water or a protonic acid aqueous solution. When using a proton acid aqueous solution as a washing solvent, it is preferable to contain the same proton acid as the proton acid used at the time of heating and mixing.

  In the present invention, in addition to the metal impurities contained in the indole derivative trimer, the organic solvent, oxidant component, unreacted raw material, low molecular weight component, by-product, etc. used in the production process of the indole derivative trimer are also included. By removal, an indole derivative trimer having a high purity, in particular, a purity of 95% or more can be obtained.

  Next, the structure and manufacturing method of the electrochemical cell will be described.

  The electrochemical cell of the present invention is composed of an electrode active material containing a high-purity indole derivative trimer obtained by the method of the present invention, contains an electrolyte containing a proton source, and is charged and discharged. This is an electrochemical cell in which protons act as charge carriers in the oxidation-reduction reaction involved.

  As an electrode active material used in such an electrochemical cell, in addition to the high-purity indole derivative trimer obtained by the method of the present invention, as a proton-conducting compound, in a solution containing a proton source, redox As long as it has properties, it is not particularly limited.

  For example, polyaniline, polythiophene, polypyrrole, polyacetylene, poly-p-phenylene, polyphenylene vinylene, polyperinaphthalene, polyfuran, polythienylene, polypyridinediyl, polyisothianaphthene, polyquinoxaline, polypyridine, polypyrimidine, polyindole, polyaminoanthraquinone, Π-conjugated polymers such as polyimidazole and their derivatives, hydroxyl group-containing polymers such as polyanthraquinone and polybenzoquinone (quinone oxygen is converted into a hydroxyl group by conjugation), copolymerized from two or more monomers Conductive polymers and the like are mentioned, and by applying doping to these polymers, a redox pair is formed and conductivity is exhibited. These compounds are selectively used as a positive electrode and a negative electrode active material by appropriately adjusting the difference in oxidation-reduction potential.

  In particular, in the present invention, it is preferable to use an indole derivative trimer represented by the general formula (1) as the positive electrode active material and a polyphenylquinoxaline derivative represented by the following general formula (3) as the negative electrode active material.

（式中Ｒ”は、各々独立に式（１）のＲと同様の意味を示す。）

(In the formula, each R ″ independently represents the same meaning as R in the formula (1).)

  FIG. 1 shows a configuration diagram of the electrochemical element of the present invention, and FIG. 2 shows a configuration diagram of the electrochemical cell.

  The positive electrode 2 is formed on the positive electrode current collector 1 and the negative electrode 3 is formed on the negative electrode current collector 4, which are bonded together via an insulating layer (separator) 5, and only protons are used as charge carriers. Is involved. Moreover, the electrolyte solution is filled with an aqueous solution or a non-aqueous solution containing a proton source, and sealed with a gasket 6 to produce an electrochemical device (FIG. 1). Next, the terminal plate 7 is provided on the positive electrode side and the negative electrode side of the electrochemical device, and an electrochemical cell having a configuration of one electrochemical device can be manufactured.

  Here, the positive electrode 2 and the negative electrode 3 are respectively an active material and a conductive additive (for example, fibrous carbon (trade name “VGCF”, manufactured by Showa Denko) or particulate carbon (made by Ketjen Black International, product name “ Ketjen Black EC600JD ") is mixed with 1 to 50 parts by mass, preferably 10 to 30 parts by mass with respect to the active material. This mixed powder is pressure-molded at room temperature to 400 ° C, preferably 100 to 300 ° C. Alternatively, a slurry in which the mixture is dispersed in an arbitrary organic solvent or water is prepared, and if necessary, 1 to 20 parts by mass, preferably 5 to 10 parts by mass of the binder is mixed with the active material, and conductive. It can be produced by printing on a substrate by screen printing or the like and drying.

  Although it does not specifically limit as a binder seed | species, Fluorine-type polymers, such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE), are preferable. The molecular weight is not particularly limited as long as it is in a range that can be dissolved in the solvent to be used.

As the electrolytic solution, an aqueous solution or non-aqueous solution containing protons is used. For example, the acid is an organic acid or an inorganic acid, specifically, an inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluorosilicic acid, saturated monocarboxylic acid, etc. Examples thereof include organic acids such as acids, aliphatic carboxylic acids, oxycarboxylic acids, p-toluenesulfonic acid, polyvinylsulfonic acid, and lauric acid. The proton content is preferably 10 ⁻³ mol / l to 18 mol / l, and more preferably 10 ⁻¹ mol / l to 7 mol / l.

  The insulating layer (separator) 5 can be used without particular limitation as long as it can electrically insulate between the positive electrode and the negative electrode of the electrochemical cell and is a porous material that does not inhibit the movement of the electrolyte, particularly protons. For example, a polyolefin-type porous membrane and an ion exchange membrane are mentioned. Although it does not specifically limit as thickness, Usually, 10-200 micrometers, More preferably, it is 10-80 micrometers.

  The outer shape of the electrochemical cell can be a coin type or a laminate type, and is not particularly limited.

  The electrochemical cell of the present invention can operate so that only protons act as charge carriers in the oxidation-reduction reaction associated with charge / discharge, more specifically, contains an electrolyte containing a proton source and accompanies charge / discharge. In the electron transfer of the oxidation-reduction reaction, those capable of operating so that only the adsorption / desorption of protons of the electrode active material is involved are preferable.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited only to these Examples.

Production Example 1 (Production of indole derivative trimer)
A 200 ml three-necked flask was charged with 10 ml of acetonitrile, and 1.42 g of methyl indole-6-carboxylate was dissolved. On the other hand, the oxidant solution was prepared by adding 16.2 g of anhydrous ferric chloride and 5.4 g of water to 40 ml of acetonitrile and dissolving it, followed by stirring for 10 minutes. Next, the prepared oxidant solution was added dropwise to the acetonitrile solution of the indole-6-carboxylate monomer in the flask over 30 minutes, followed by stirring at 60 ° C. for 10 hours. The reaction solution turned from pale yellow to green. Here, the reaction was stopped, suction filtered, washed with acetonitrile and then methanol at room temperature, dried in air at 120 ° C. for 5 hours, and 6,11-dihydro-5H-diindolo [2,3-a: 2.12 g of 2 ′, 3′-c] carbazole-3,8,13-tricarboxylic acid trimethyl ester (methyl indole-6-carboxylate) was obtained as a green powder.

  The purity of the obtained indole derivative trimer was calculated from the area value by HPLC analysis, and the amount of metal impurities was calculated by ICP emission analysis. These results are shown in Table 1.

Example 1
About 1 g of the trimer obtained in Production Example 1 was transferred to a 200 ml beaker, 15 g of 5 wt% sulfuric acid aqueous solution was added as a solvent, stirred for 5 minutes at room temperature, and then the heater temperature was raised to 180 ° C. Held for 30 minutes. 8 g of 1H-imidazole was mixed with the mixed solvent, and the mixture was further maintained at the same temperature with stirring for 10 minutes. Thereafter, the trimer and the solvent were separated by suction filtration, and the filtered trimer was lightly washed with boiling water and then dried to obtain a light green crystal. At this time, the filtrate was yellow.

Example 2
This was carried out in the same manner as in Example 1 except that 20 wt% sulfuric acid aqueous solution was used as a solvent.

Example 3
This was carried out in the same manner as in Example 1 except that 40 wt% sulfuric acid aqueous solution was used as a solvent.

Example 4
This was carried out in the same manner as in Example 1 except that 20 wt% hexafluorophosphoric acid aqueous solution was used as a solvent.

Example 5
It implemented like Example 1 except having used ion-exchange water as a solvent.

Example 6
About 1 g of the trimer obtained in Production Example 1 was heated to 260 ° C., a mixed solvent consisting of 15 g of 20 wt% hexafluorophosphoric acid aqueous solution and 8 g of 1H-imidazole was boiled, then both were mixed, and the heater temperature Stir at 180 ° C. for 5 minutes. Thereafter, filtration, washing and drying were carried out in the same manner as in Example 1 to obtain a pale green crystal.

Example 7
The treatment was performed in the same manner as in Example 1 except that the heater temperature was set to 80 ° C.

Comparative Example 1
About 1 g of the trimer obtained in Production Example 1 is transferred to a 200 ml beaker, and 15 g of a 20 wt% sulfuric acid aqueous solution is added as a solvent, stirred at room temperature for 30 minutes, filtered and dried, and then dark green A crystalline product was obtained.

  The trimer purity and the amount of metal impurities in the crystals obtained in Examples 1 to 7 and Comparative Example 1 were measured in the same manner as described above. The amount of dopant was calculated by ion chromatography analysis. The results are also shown in Table 1.

(Resistivity measurement)
The crystals produced in Examples 1, 2, 3, 5, and 7 and Comparative Example 1 were formed into electrodes having a thickness of 200 μm by press molding, and the electrode resistivity was measured using a four-terminal resistance measuring instrument. . The results are also shown in Table 1.

(CV test)
A CV test was performed on the crystals manufactured in Examples 1, 2, 3, 5, 7 and Comparative Example 1, and the CV capacity was measured.

  The test sample was prepared by mixing each crystalline substance with fibrous carbon VGCF as a conductive auxiliary agent in a mass ratio of 7: 3, and adding dimethylformamide (DMF) to this mixture to make a paste, 50 mm × 5 mm The carbon sheet was formed into a film and dried at 120 ° C. for 1 hour to produce.

  The obtained test sample was immersed in a 20 wt% sulfuric acid aqueous solution, and the sweep potential was 200 to 1200 mV, and the sweep rate was 20 mV / sec. A cyclic voltammetry (CV) curve was measured under the following conditions. An Ag / AgCl electrode was used as a reference electrode, and platinum was used as a counter electrode.

(Production of electrochemical cell and leakage current characteristic test)
As the positive electrode active material, the crystals produced in Examples 1, 2, 3, 5, and 7 and Comparative Example 1 were used, respectively, fibrous carbon VGCF as a conductive auxiliary agent, and polyvinylidene fluoride (average molecular weight 1,100) as a binder. Selected. These were adjusted to a mass ratio of 69: 23: 8 in the order described, and stirred and mixed with a blender. The mixed powder was put into a 10 mm square mold and subjected to pressure molding at 200 ° C. for 1 minute to obtain a positive electrode.

  For the negative electrode, polyphenylquinoxaline, a proton conductive polymer, was used as an active material, and conductive carbon (“Ketjen Black EC600JD” trade name) was selected as a conductive auxiliary agent. The mass ratio was adjusted to 75:25 in the order of these descriptions, and the mixture was stirred and mixed with a blender. This mixed powder was put into a 10 mm square mold and subjected to pressure molding at 300 ° C. for 2 minutes to obtain a negative electrode.

  A 20 wt% sulfuric acid aqueous solution was used as the electrolytic solution, and a 50 μm thick porous nonwoven fabric was impregnated with the electrolytic solution as a separator.

  The resulting positive electrode and negative electrode are opposed to each other through this separator, and are bonded together, covered with a gasket to produce an electrochemical device, and terminal plates are provided on both sides of the positive and negative electrodes. Was made.

  The cell leakage current was measured for the electrochemical cell thus obtained. The measurement was performed at 60 ° C. under charging conditions CCCV: 1 mA-2.5 V, 24 hours, and the current value at the end of charging was measured.

  The results are also shown in Table 1.

  As shown in Table 1, compared to Comparative Example 1 in which only the acid treatment was performed at room temperature (25 ° C.), it is clear that the trimer purity is improved and the metal impurities are extremely reduced in the Example of the present invention. It became.

  In addition to Example 3, it was recognized that the CV capacity increased in correlation with the analysis results, and the leakage current of the electrochemical cell was significantly reduced.

  From the analysis results of each example, the anion of the used proton acid is doped, and from Examples 1, 2, 3, 5, and 7, the doping amount and the resistivity depend on the proton acid concentration used. It was confirmed that a high purity indole derivative trimer doped with an arbitrary proton acid anion was obtained.

  From the results of Examples 1 to 3, it was found that good results were obtained when the concentration of the protonic acid was 30% by mass or less. When 40% by mass of the protonic acid of Example 3 was used, a decrease in CV capacity was observed, and a result suggesting the structural deterioration of the indole derivative trimer was obtained.

  Moreover, as shown in Example 5, it was confirmed that the amount of metal impurities can be reduced without using a protonic acid.

  From Examples 2 and 4, it was confirmed that a highly pure indole derivative trimer was obtained regardless of the type of protonic acid.

  From Examples 4 and 6, it was confirmed that the metal impurities can be similarly removed by heating after mixing the protonic acid or by adding the protonic acid to the heated trimer.

  In addition, from Examples 1 to 7, it was confirmed that there was a difference in the removal effect of metal impurities depending on the reaction temperature, and a good removal effect was obtained when the temperature was 100 ° C. or higher.

It is sectional drawing of the electrochemical element which becomes one Embodiment of this invention. It is sectional drawing of the electrochemical cell which becomes one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode collector 2 Positive electrode 3 Negative electrode 4 Negative electrode collector 5 Insulating layer (separator)
6 Gasket 7 Terminal board

Claims (18)

A method for purifying an indole derivative trimer, which removes a metal impurity from an indole derivative trimer containing a metal impurity, wherein at least water is added to the indole derivative trimer represented by the following general formula (1) containing the metal impurity. Purification comprising mixing a imidazole compound that forms a complex with a metal impurity under heating in a solvent containing the mixture, and separating the indole derivative trimer from which the metal impurity has been removed from the resulting mixture. Method.

(In the formula, each R is independently a hydrogen atom, hydroxyl group, carboxyl group, nitro group, vinyl group, halogen atom, acyl group, cyano group, amino group, trifluoromethyl group, sulfonyl group, sulfonic acid group, Represents a trifluoromethylthio group, a carboxylic acid ester group, a sulfonic acid ester group, an alkoxyl group, an alkylthio group, an aryloxy group, an arylthio group, an alkyl group, an aryl group, or a heterocyclic compound residue.) The purification method according to claim 1, wherein the indole derivative trimer containing a metal impurity is obtained by chemically polymerizing an indole derivative represented by the following formula (2) with an oxidizing agent comprising a metal compound.

(In the formula, each R independently represents the same meaning as R in the general formula (1).)   2. The purification method according to claim 1, wherein the indole derivative trimer containing the metal impurity and the protonic acid are mixed simultaneously with the imidazole compound or before mixing with the imidazole compound.   The purification method according to claim 3, wherein the protonic acid is mixed as an aqueous solution having a concentration of 30% by mass or less.   The purification method according to any one of claims 1 to 4, wherein the metal impurity contains iron as a metal component.   The purification method according to any one of claims 1 to 5, wherein the imidazole compound is 1H-imidazole.   A mixture of the indole derivative trimer containing the metal impurity and the water-containing solvent, imidazole compound and / or protonic acid is heat-treated in a temperature range of 80 ° C. or higher and below the reflux temperature of the mixture. The purification method according to any one of claims 1 to 6.   The indole derivative trimer containing the metal impurities is heated to a temperature range of 100 to 300 ° C, and then the solvent containing water, the imidazole compound and / or the protonic acid are mixed. The purification method according to any one of the above. A method for producing an electrode active material for an electrochemical cell containing an electrolyte containing a proton source and capable of operating so that protons act as charge carriers in an oxidation-reduction reaction associated with charge and discharge. The indole derivative trimer represented by (1) is mixed with an aqueous solution of a protonic acid containing an anion of the same chemical species as the electrolyte used in the electrochemical cell under heating, and / or simultaneously with a metal impurity and a metal. An electrode active material comprising the steps of: mixing an imidazole compound that forms a complex; and separating the indole derivative trimer doped with a proton acid anion from which metal impurities have been removed. Production method.

(In the formula, each R is independently a hydrogen atom, hydroxyl group, carboxyl group, nitro group, vinyl group, halogen atom, acyl group, cyano group, amino group, trifluoromethyl group, sulfonyl group, sulfonic acid group, Represents a trifluoromethylthio group, a carboxylic acid ester group, a sulfonic acid ester group, an alkoxyl group, an alkylthio group, an aryloxy group, an arylthio group, an alkyl group, an aryl group, or a heterocyclic compound residue.) The electrode active material according to claim 9, wherein the indole derivative trimer containing a metal impurity is obtained by chemical polymerization of an indole derivative represented by the following formula (2) with an oxidizing agent comprising a metal compound. Manufacturing method.

(In the formula, each R independently represents the same meaning as R in the general formula (1).)   The method for producing an electrode active material according to claim 9 or 10, wherein the aqueous solution of the protonic acid has a concentration of 30% by mass or less.   The method for producing an electrode active material according to claim 9, wherein the metal impurity contains iron as a metal component.   The purification method according to any one of claims 9 to 12, wherein the imidazole compound is 1H-imidazole.   The indole derivative trimer containing the metal impurity and the mixture of the aqueous solution of the proton acid and / or the imidazole compound are heat-treated at a temperature range of 80 ° C. or higher and lower than the reflux temperature of the mixture. The method for producing an electrode active material according to any one of 9 to 13.   The indole derivative trimer containing the metal impurity is heated to a temperature range of 100 to 300 ° C., and then the aqueous solution of the protonic acid or / and the imidazole compound are mixed. A method for producing the electrode active material according to Item.   The electrode active material containing the indole derivative trimer obtained by the manufacturing method of any one of Claims 9 thru | or 15.   The electrode active material according to claim 16, wherein the purity of the indole derivative trimer is 95% or more.   18. An electrochemical cell comprising an electrolyte containing a proton source and capable of operating so that protons act as charge carriers in a redox reaction associated with charge and discharge, wherein the electrode according to claim 16 or 17 is used as an electrode active material. An electrochemical cell containing an active material.

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