JP4475002B2 - Ionic conductor, method for producing the same, and electrochemical device - Google Patents

Description

  The present invention relates to an ion conductor, a method for producing the same, and an electrochemical device.

  Fuel cells are attracting attention as a next-generation environment-friendly electric energy generator due to their high efficiency and cleanliness, and are being actively developed in various fields.

  Since fuel cells have a strong influence on the properties of proton conductors due to the temperature and conditions of use, the fuel cells themselves can be broadly classified according to the type of proton conductor used. As described above, the characteristics of the proton conductor to be used greatly affect the fuel cell performance. Therefore, improvement of the performance of the proton conductor is a great key for improving the performance of the fuel cell.

As a proton conductor, research using a compound formed by combining a basic polymer and an acid molecule has been reported (for example, see Non-Patent Document 1 described later). In addition, an example in which a fullerene compound having a proton dissociable group such as a sulfate ester group (—OSO ₃ H) or a sulfonic acid group (—SO ₃ H) is used as a proton conductor has been reported. It exhibits a proton conductivity of 10 ⁻² S / cm.

Prog. Polym. Sci., 2000, 1463-1502

  However, when a compound comprising a combination of the basic polymer and the acid molecule as described above is used as a proton conductor to constitute a fuel cell, water generated during use of the fuel cell or alcohols (eg, methanol) The low molecular acid is dissolved in the solution), and the proton conduction is lowered.

  When a fullerene compound in which a proton-dissociable group is bonded to a fullerene molecule is used as a proton conductor, the fullerene compound is an alcohol (for example, methanol solution) that is a fuel, or water that is generated when a fuel cell is used. Therefore, it is physically unstable and causes a decrease in proton conduction.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an ion conductor that is insoluble in water and fuel and can conduct stable ion conduction of protons and the like. The manufacturing method and an electrochemical device are provided.

  That is, the present invention relates to an ion dissociable group on at least one carbon material selected from the group consisting of fullerene molecules, carbon-based clusters, and linear or cylindrical carbon structures. And a derivative of a substance having a basic group; and an ionic conductor.

  Further, an ion dissociable group is bonded to at least one carbon substance selected from the group consisting of fullerene molecules, clusters mainly composed of carbon, and linear or cylindrical carbon structures. And a polymer of a substance having a basic group are dissolved in a solvent to form a homogeneous solution, and the process for removing the solvent is concerned with a method for producing an ionic conductor.

  Further, an ion dissociable group is bonded to at least one carbon substance selected from the group consisting of fullerene molecules, clusters mainly composed of carbon, and linear or cylindrical carbon structures. And a polymer of a substance having a basic group, each of which is dissolved in a solvent to form a homogeneous solution, and the homogeneous solution is mixed to recover an insoluble matter. This relates to a method for manufacturing a body.

  Furthermore, an ion dissociative group is bonded to a carbon substance composed of at least one selected from the group consisting of fullerene molecules, clusters mainly composed of carbon, and linear or cylindrical carbon structures. And a monomer of a substance having a basic group; and polymerization of the mixture to produce an ionic conductor having the derivative and the polymer of the substance having the basic group. The manufacturing method of an ionic conductor which has a process to do.

  Further, the present invention comprises a first electrode, a second electrode, and an ionic conductor sandwiched between the two electrodes, the ionic conductor comprising a fullerene molecule and a cluster mainly composed of carbon, A derivative in which an ion dissociable group is bonded to at least one carbon substance selected from the group consisting of a linear or cylindrical carbon structure; a polymer of a substance having a basic group; The present invention relates to an electrochemical device.

  In the present invention, the above “ion dissociable group” means a group from which ions such as protons (hereinafter the same) can be separated by ionization. Further, the “basic group” described above promotes the dissociation of ions by the ion dissociable group, receives the dissociated ions, and further converts the received ions into the adjacent ion dissociable group or other groups. To the basic group.

  According to the ionic conductor and the method for producing the same of the present invention, an ion complex is formed between the derivative formed by bonding the ion dissociable group and the polymer of the substance having the basic group. It is insoluble in water and methanol solution and is physically stable. Therefore, stable ion conduction of protons and the like can be performed.

  In addition, according to the electrochemical device of the present invention, the ion conductor sandwiched between the first electrode and the second electrode has the above-described excellent characteristics from the ion conductor of the present invention. Thus, the same effect as described above can be achieved. Therefore, it is possible to realize a device having excellent performance that can be started up at a low temperature such as room temperature and during drying.

  In the ionic conductor according to the present invention, the derivative having the ion dissociable group bonded thereto and the substance having the basic group are preferably mixed.

Further, as described later, a proton (H ⁺ ) dissociable group is used as the ion dissociable group, and can function as a proton conductor.

FIG. 1 is a schematic view of an example of an ionic conductor according to the present invention. In FIG. 1, the fullerene molecule (for example, C ₆₀ ) is used as the carbon material, the proton dissociable group represented by —PO (OH) ₂ is used as the ion dissociable group, and This is a case where polyvinyl imidazole is used as the polymer of the substance having the basic group.

  The ionic conductor according to the present invention is formed by forming an ion complex with the derivative and the polymerized substance having the basic group, so that it is insoluble in water, methanol solution, etc. stable. Therefore, for example, when used in a fuel cell or the like, it is possible to realize a device having excellent performance that can be started up at a low temperature such as room temperature and during drying.

  Here, in the ionic conductor according to the present invention, the ion dissociable group and the basic group may be bonded to the carbon substance, and in this case, the same excellent ion conduction performance as described above have.

  As the carbon material to be the base, at least one selected from the group consisting of the fullerene molecule, the cluster mainly composed of carbon, and the linear or cylindrical carbon structure is used. It is important that the ion conductivity is greater than the electron conductivity after the introduction of an ion dissociable group.

The fullerene molecule as the carbon substance is not particularly limited as long as it is a spherical cluster molecule, but usually C ₃₆ , C ₆₀ (see FIG. 2 (A)), C ₇₀ (see FIG. 2 (B)), C ₇₆ , C ₇₈ , C ₈₀ , C ₈₂ , C ₈₄ , C ₈₆ , C ₈₈ , C ₉₀ , C ₉₂ , C ₉₄ , C _96, etc., or a fullerene molecule alone or a mixture of two or more thereof is preferably used. It is done.

  These fullerene molecules were discovered in the mass spectrometry spectrum of a cluster beam by laser ablation of carbon in 1985 (Kroto, HW; Heath, JR; O'Brien, SC; Curl, RF; Smalley, RE Nature 1985. 318, 162.). The manufacturing method was actually established five years later. In 1990, a method of manufacturing a carbon electrode by an arc discharge method was found, and since then, the fullerene has been attracting attention as a carbon-based semiconductor material. I came.

  For example, when a large number of the derivatives formed by bonding the ion dissociable group to the fullerene molecule are aggregated, the ion conductivity exhibited as a bulk is a large amount of the ion dissociative property originally contained in the molecule. Since ions derived from the group are directly involved in the movement, they can be used continuously even in a dry atmosphere.

  In addition, the fullerene molecule has particularly electrophilic properties, and this greatly contributes to the promotion of ionization of hydrogen ions in the proton dissociable group as the ion dissociable group having high acidity. It is thought that it exhibits excellent ionic conductivity. In addition, since a considerable number of the ion dissociable groups can be bonded in one fullerene molecule, the number density of the hydrogen ions involved in conduction per unit volume of the conductor becomes very large. Expresses the electrical conductivity.

  Since most of the derivatives constituting the ionic conductor according to the present invention are composed of carbon atoms of the fullerene molecule, they are light in weight, hardly change in quality, and contain no contaminants. The production cost of the fullerene molecule is also rapidly decreasing. From the viewpoint of resources, environment, and economy, the fullerene molecule is considered to be a carbon material that is closer to the ideal than any other material.

  In the present invention, instead of the derivative having the fullerene molecule as a base, a cluster made of carbon powder is obtained, for example, by an arc discharge method of a carbon-based electrode, and the ion dissociable group is bonded to the carbon powder. Cluster derivatives can be used.

  Here, the cluster is usually an aggregate formed by combining or aggregating several to several hundred atoms, and at the same time the ion conduction performance is improved by the aggregate (aggregate), It retains chemical properties and has sufficient film strength, making it easy to form a layer. This cluster is mainly composed of carbon, and is an aggregate formed by bonding several to several hundred carbon atoms regardless of the type of carbon-carbon bond. However, it is not necessarily composed of only 100% carbon clusters, and other atoms may be mixed. Including such a case, an aggregate in which a large number of carbon atoms occupy is referred to as a carbon cluster.

  Since the ionic conductor according to the present invention is mainly composed of the carbon cluster as a base material bonded with the ionic dissociable group, ions are easily dissociated even in a dry state, and ionic conductivity is started. An effect similar to that of the ionic conductor comprising the fullerene derivative described above can be obtained. In addition, since the carbon cluster category includes many kinds of carbonaceous materials as will be described later, an effect of wide selection of carbonaceous raw materials can be achieved.

  In this case, the use of the carbon cluster as a base material requires that a large amount of the ion dissociable group be bonded in order to impart good ion conductivity, which is enabled by the carbon cluster. Because. However, in this case, the acidity of the solid ionic conductor is remarkably increased, but unlike other normal carbonaceous materials, the carbon cluster is less susceptible to oxidative degradation, has excellent durability, and the constituent atoms are closely bonded. Therefore, even if the acidity is high, bonds between atoms do not break (that is, they are difficult to change chemically), and the film structure can be maintained.

  The ion conductor having such a configuration can also exhibit high ion conductivity even in a dry state, and there are various types as shown in FIGS. It is wide.

  First, what is shown in FIG. 3 is a sphere or spheroid made up of a large number of carbon atoms, or various carbon clusters having a closed surface structure similar to these (including molecular fullerenes). Show). On the other hand, FIG. 4 shows various carbon clusters in which a part of the spherical structure is missing. In this case, the structure is characterized by having an open end, and such a structure is often seen as a by-product in the process of producing fullerene by arc discharge. When most of the carbon atoms of the carbon cluster are SP3 bonded, various clusters having a diamond structure as shown in FIG. 5 are obtained.

  A cluster in which most carbon atoms are SP2 bonded has a planar structure of graphite, or a fullerene or a nanotube, or a partial structure. Among them, those having a graphite structure are not preferable as the base material of the ion conductor because many of them have electron conductivity in the cluster.

  On the other hand, SP2 bonds of fullerenes and nanotubes contain SP3 bond elements in part, and therefore many of them do not have electronic conductivity, and are preferable as a base material for ion conductors.

  Moreover, the said derivative | guide_body may consist of the chemical or physical coupling body or bridge | crosslinking body of the said carbon substances. For example, FIG. 6 shows various cases where clusters are bonded to each other, and such a structure can also be applied to the present invention.

  The carbon cluster derivative can be directly pressure-molded into a film shape or a pellet shape without a binder. In the present invention, the base carbon cluster preferably has a long axis length of 100 nm or less, particularly preferably 100 mm or less, and the number of groups introduced therein is preferably 2 or more.

  Further, the carbon cluster is preferably a cage structure (the fullerene molecule or the like) or a structure having an open end at least in part. The fullerene having such a defect structure has the reactivity of the fullerene molecule, and at the same time, the defect portion, that is, the open portion has a higher reactivity. Accordingly, introduction of the ion dissociable group is promoted, a higher group introduction rate is obtained, and high ion conductivity is obtained. Moreover, it becomes possible to synthesize in large quantities compared with the fullerene molecule, and it can be produced at a very low cost.

  On the other hand, it is preferable to use the cylindrical or linear carbon structure as the base of the ionic conductor according to the present invention. The cylindrical carbon structure is preferably a carbon nanotube having a tube shape, for example, a diameter of several nm or less, typically 1 to 2 nm. The linear carbon structure is preferably a carbon fiber having a fiber shape, for example, a diameter of several nanometers or more, and a large one having a diameter of 1 μm.

  The carbon nanotube or the carbon fiber can easily emit electrons in the structure and can have a very large surface area, so that the proton propagation efficiency can be further improved.

  The graphene structure (cylindrical structure) of the multi-walled carbon nanotube as shown in the perspective view of FIG. 7A and the partial cross-sectional view of FIG. 7B is a high-quality carbon nanotube without defects, which is an electron. It is known to have very high performance as a release material. The carbon fiber having a structure as shown in the perspective view of FIG. 7C is also preferably used in the present invention.

  The carbon nanotube or the carbon fiber that can be suitably used here can be produced by an arc discharge method or a chemical vapor deposition method (thermal CVD method).

On the other hand, in the ion conductor according to an embodiment of the present invention, the ion-dissociative _{group, -SO 3 M, -PO (OM} ) 2, -SO 2 NMSO 2 -, - SO 2 NM 2, -COOM, = CPO ( OM) ₂ and ═C (SO ₃ M) ₂ (wherein M is a cation group, for example, an active hydrogen group), and is preferably at least one selected from the group consisting of.

In the ionic conductor according to the present invention, at least a functional group having the ion dissociable group is bonded to the carbon substance, and the functional group is -A-SO ₃ M, -A-PO (OM). ₂ , -A-SO ₂ NMSO ₂ -R ⁰ , -A-SO ₂ NM ₂ and -A-COOM [where A is -O-, -R-, -O-R-, -R-O-, —O—R—O— or —R—O—R′— (R and R ′ may be the same or different from each other, CxHy or CxFyHz (1 ≦ x ≦ 20, 1 ≦ y ≦ 40 , 0 ≦ z ≦ 39).), M is a group that becomes a cation (for example, an active hydrogen group), and R ⁰ is —CF ₃ or —CH ₃ . It may be at least one selected from the group consisting of

Further, together with the ion dissociable group, an electron withdrawing group such as a nitro group, a carbonyl group, a carboxyl group, a nitrile group, a halogenated alkyl group, a halogen atom (fluorine, chlorine, etc.) may be introduced into the carbon cluster. . Specifically, —NO ₂ , —CN, —F, —Cl, —COOR, —CHO, —COR, —CF ₃ , —SO ₃ CF ₃ and the like (wherein R represents an alkyl group). When the electron-withdrawing group coexists in this way, due to the electron-withdrawing effect, ions such as protons are easily dissociated from the ion-dissociable group, and the dissociated ions are It becomes easier to move through the group and the basic group.

  The number of the ion dissociable groups introduced into the carbon cluster may be arbitrary within the range of the number of carbons constituting the carbon cluster, but is desirably 5 or more. For example, in the case of the fullerene molecule, the number of the ion dissociable groups is less than half of the number of carbons constituting the fullerene in order to leave the fullerene π-electron property and to provide effective electron withdrawing property. Is preferred.

  In order to introduce the ion dissociable group into the carbon cluster, for example, the carbon cluster is first synthesized by arc discharge of a carbon-based electrode, and then the carbon cluster is acid-treated (using sulfuric acid or the like), Treatment such as hydrolysis may be performed, or sulfonation or phosphate esterification may be appropriately performed. As a result, a carbon cluster derivative (carbon cluster having an ion dissociable group) as a target product can be easily obtained.

For example, when a large number of fullerene derivatives having an ion dissociable group introduced into carbon cluster fullerene are aggregated, the ionic conductivity exhibited as an aggregate of bulk or fullerene derivatives is a large amount originally contained in the molecule. Since protons derived from the ion dissociable group (for example, OSO ₃ H group) are directly involved in movement, it is not necessary to take in hydrogen, protons, etc. originating from water vapor molecules from the atmosphere, There is no need to absorb moisture from the outside air and there are no restrictions on the atmosphere. Since a large number of the ion dissociable groups can be introduced into one fullerene molecule, the number density of the hydrogen ions involved in conduction per unit volume of the conductor is greatly increased. This is the reason why the ionic conductor according to the present invention exhibits effective conductivity.

  As described above, the carbon cluster having the ion dissociable group itself has a structural property that the spatial density of the functional group of the acid is high, an electronic property of the base carbon cluster (for example, fullerene), etc. As a result, ions such as protons can be dissociated and a structure that can easily hop between the sites can be realized, so that conduction of ions such as protons is realized even in a dry state.

  However, the aforementioned derivatives such as the fullerene derivatives alone are soluble in water, methanol solution, and the like, and when this is used as an ionic conductor for a fuel cell or the like, proton conductivity is lowered. In contrast, the ion conductor based on the present invention as illustrated in FIG. 1 is formed by forming an ion complex with the derivative and the substance having the basic group that has been polymerized. It is insoluble in a methanol solution and is physically stable. For example, when used in a fuel cell or the like, it is possible to realize a device having excellent performance that can be started up at a low temperature such as room temperature and when dried.

  As the polymer of the substance having the basic group, a polymer of a compound containing at least one of N atom, O atom and S atom as a constituent element is preferable.

  Moreover, it is preferable that the polymer of the said substance contains at least 1 sort (s) of the structural part represented by following Structural formula. All of these are Lewis basic groups including an atom having an unshared electron pair.

  In addition, the basic site of the polymer of the substance is an amino group, pyrrolidone group, pyridine group, imidazole group, pyrimidine group, piperazine group, pyrrole group, pyrrolidine group, pyrazole group, benzimidazole group, phenylimidazole group or pyrazine. It is preferably at least one selected from the group consisting of groups.

  Furthermore, the polymer of the N atom-containing compound is preferably a polymer of a heterocyclic compound.

  Specific examples of the polymer of the substance having the basic group include imidazole, pyrrole, pyrrolidine, pyridine, pyrazole, benzimidazole, phenylimidazole, vinylimidazole, pyrazine, piperazine, as shown in FIG. A polymer having a structure of at least one compound selected from the group consisting of oxazole, isoxazole, thiazole, isothiazole, furan and thiophene, or derivatives thereof can be used. More specifically, it is preferable to use a polymer such as poly [4-vinylimidazole] as shown in FIG. Of course, it is needless to say that the present invention is not limited to these.

  Moreover, as a polymer of the said substance which has the said basic group, the compound shown in FIG. 9 can be mentioned, for example.

  The amount of the polymer in the substance having the basic group is closely related to the number of the ion dissociable groups. Actually, the ratio of the ion dissociable group to the basic group (the basic group / the ion dissociable group) is 20 or less, preferably 0.05 to 20 in molar ratio. Thus, the effect can be remarkably exhibited when the derivative and the polymer of the substance having the basic group are mixed.

  When the molar ratio exceeds 20, the density of the ion dissociable group with respect to the entire ionic conductor may decrease, or the volume occupied by the polymer of the substance having the basic group may become too large. On the contrary, there is a possibility that an adverse effect of decreasing the ionic conductivity of protons or the like starts to appear. On the contrary, when the molar ratio is less than 0.05, the number of the basic groups derived from the polymer of the substance is less than 1/20 of the number of the ion dissociable groups. Since complex formation makes it difficult to insolubilize in water or methanol, the ionic conductivity inherent in the ionic conductor based on the present invention may not be sufficiently exhibited.

  The method for producing an ionic conductor according to the present invention includes at least one selected from the group consisting of the fullerene molecule, the cluster mainly composed of carbon, and the linear or cylindrical carbon structure. The carbon material is mixed with the derivative obtained by bonding the ion dissociable group; the monomer of the substance having the basic group; and then heat polymerization is performed. Thereby, it is possible to produce an ionic conductor according to the present invention in which an ion complex is formed by the derivative and the polymer of the substance.

  Moreover, the method for producing an ionic conductor according to the present invention includes at least one selected from the group consisting of the fullerene molecule, the cluster mainly composed of carbon, and the linear or cylindrical carbon structure. Dissolving the derivative obtained by bonding the ion dissociable group to the carbon substance; and the polymer of the substance having the basic group into a uniform solution; and Removing.

  Moreover, the method for producing an ionic conductor according to the present invention includes at least one selected from the group consisting of the fullerene molecule, the cluster mainly composed of carbon, and the linear or cylindrical carbon structure. A step of dissolving each of the derivative obtained by binding the ion dissociable group to the carbon substance and a polymer of the substance having the basic group into a uniform solution by dissolving them in a solvent, and And collecting the insoluble matter by mixing the homogeneous solution.

  The derivative alone is soluble in the solvent. For example, by making the derivative and the polymer of the substance into a uniform solution, an ion complex is formed between the derivative and the polymer of the substance, and the derivative is insoluble in the solvent. Therefore, the ionic conductor based on this invention can be obtained as said insoluble matter.

  Examples of the solvent include hydrocarbon solvents such as toluene, butane, pentane, hexane, and cyclohexane, alcohols such as methanol, ethanol, 1-propanol, and 2-propanol, phenols such as phenol and cresol, diethyl ether, and dioxane. Inorganic solvents such as ethers such as tetrahydrofuran, ketones such as acetone and methyl ethyl ketone, nitrogen compounds such as acetonitrile, pyridine, N, N-dimethylformamide, and dimethyl sulfoxide, sulfur compounds, and water can be used.

  The ion conductor based on this invention can be shape | molded by press-molding into a desired shape, for example, a pellet or a thin film, or filtering as it is. In this case, a binder is unnecessary, and this is effective in increasing the conductivity of ions such as protons and achieving weight reduction of the ionic conductor. In particular, the polymer of the substance having the basic group also functions as a binder and imparts good film formability and moldability. Of course, it is also possible to add a third component as a binder. As the polymer material usable as the third component, the conductivity of ions such as protons is not hindered as much as possible, it has film forming properties, has chemical, thermal and mechanical stability, There is no particular limitation as long as the leak can be kept low. Usually, those having no electronic conductivity and good stability are used. Specific examples include polyfluoroethylene and polyvinylidene fluoride. The polymer binder as the third component may be arbitrarily mixed in the production process of the method for producing an ionic conductor based on the present invention as described above, for example.

  In addition to the above, first, the polymer of the substance having the basic group is formed into a film shape, and the film of the substance is doped with the derivative by immersing the film in the solution of the derivative. It is also possible to form a film made of an ionic conductor based on the present invention. Further, the derivative polymer may be doped with the derivative of the substance by allowing the derivative solution to permeate the film made of the substance polymer to form a film made of the ionic conductor according to the present invention.

  According to the ionic conductor and the method for producing the same according to the present invention, the ionic conductor has the derivative formed by bonding the ionic dissociable group, and the polymer of the substance having the basic group. An ion conductor that is insoluble and physically stable can be obtained.

  Further, it can be used in a dry atmosphere or in a wide temperature range including normal temperature (for example, a range of about 160 ° C. to −40 ° C.), and is dense and excellent in gas barrier properties. In addition, the polymer of the substance having the basic group promotes dissociation of ions even in a dry atmosphere, and the dissociated ions can move smoothly through the basic group. Therefore, high ionic conductivity is exhibited.

  As described above, the ion conductor according to the present invention may be added with a third component as a binder, and the third component does not hinder the conductivity of ions such as protons as much as possible, and has a film forming property. It is preferable that it has chemical, thermal and mechanical stability and can keep fuel leakage low. Specifically, in addition to the materials described above, porous polymer materials, and more preferably polyimides are used. Polyimides are particularly preferred because of their good dimensional stability.

  When the porous polymer material is used as a porous membrane, the porosity is preferably 10 to 85%, and the average pore diameter is preferably 0.05 to 5 μm. If the porosity is too low, ion conduction may be hindered. Conversely, if the porosity is too high, the mechanical strength may be reduced. If the average pore diameter is too small, it may be difficult to fill the ionic conductor according to the present invention, and conversely if too large, the holding capacity of the packing may be lowered. Moreover, it is preferable that a film thickness is 5-300 micrometers.

  By further containing the porous polymer material in the ionic conductor based on the present invention, the above-described effects of the present invention can be obtained, and the film formability, mechanical strength, and chemical strength can be further improved. Therefore, it is possible to realize an electrochemical device such as a fuel cell in which the crossover of fuel is further suppressed.

  When the porous polymer material such as polyimide is further contained, for example, the porous polymer material is first immersed in a polymer solution of the substance having the basic group, and then the porous polymer material Are filled with a polymer of the substance having the basic group. Next, after removing the solvent, the porous polymer material having the polymer of the substance is immersed in the derivative solution to form an ion complex, whereby the ion conductor according to the present invention can be produced.

  In addition, the porous polymer material is filled with a monomer solution of the substance having the basic group to induce a high molecular weight chemical reaction, and then immersed in the derivative solution to form an ion complex. The ionic conductor based on this invention may be produced by forming. The chemical reaction for increasing the molecular weight can be induced by applying external energy such as heat or light (the same applies hereinafter).

  In addition, the porous polymer material is filled with a mixed solution of the monomer having the basic group and the derivative of the substance, and an ionic conductor according to the present invention is induced by inducing a high molecular weight chemical reaction. May be produced.

  Alternatively, the porous polymer material may be filled with a mixed solution of the derivative and the polymer of the substance having a basic group, and the ionic conductor according to the present invention may be produced by removing the solvent. Good.

  Further, the porous polymer material is filled with the derivative solution, the solvent is removed, and then immersed in a polymer solution of the substance having the basic group to form an ion complex. An ionic conductor according to the invention may be made.

  The ionic conductor of the present invention can be suitably used for various electrochemical devices. That is, in a basic structure composed of a first electrode, a second electrode, and a proton conductor sandwiched between both electrodes, the ion conductor according to the present invention can be preferably applied to the proton conductor. it can.

  More specifically, an electrochemical device in which the first electrode and / or the second electrode is a gas electrode, or an electrochemical device using an active material electrode in the first electrode and / or the second electrode. For example, the ionic conductor according to the present invention can be preferably applied.

  Hereinafter, an example in which the ion conductor according to the present invention is applied to a fuel cell in which fuel is supplied to the first electrode and oxygen is supplied to the second electrode will be described.

The proton conduction mechanism of the fuel cell is as shown in the schematic diagram of FIG. 10, and the proton conducting portion 1 is sandwiched between a first electrode (for example, a hydrogen electrode) 2 and a second electrode (for example, an oxygen electrode) 3. The dissociated proton (H ⁺ ) moves from the first pole 2 side to the second pole 3 side along the direction of the arrow in the drawing.

FIG. 11 shows a specific example of a fuel cell using an ionic conductor according to the present invention for the proton conducting portion. This fuel cell has a negative electrode (fuel electrode or hydrogen electrode) 2 and a positive electrode (oxygen electrode) 3 with terminals 8 and 9 facing each other, in which the catalysts 2a and 3a are in close contact with each other, and between these two electrodes. The proton conducting part 1 is sandwiched between the two. In use, hydrogen is supplied from the inlet 12 on the negative electrode 2 side and discharged from the outlet 13 (this may not be provided). Protons are generated while the fuel (H ₂ ) 14 passes through the flow path 15, and these protons move to the positive electrode 3 side together with the protons generated in the proton conducting section 1, where they are supplied to the flow path 17 from the inlet 16. Then, it reacts with oxygen (air) 19 toward the waste outlet 18, and thereby a desired electromotive force is taken out.

  Since the ionic conductor based on this invention is used for the proton conduction part 1, the fuel cell of this structure has the same effect as mentioned above.

  Hereinafter, the present invention will be specifically described based on examples.

Example 1
As the derivative, a sulfonic acid-based fullerene derivative as shown in FIG. 12 was used, and as a polymer of the substance having the basic group, polyvinylimidazole shown in FIG. 8 (p) was used. Polyvinylimidazole was prepared based on the synthesis method of the document Macromolec. Syn., 1974, 5, 43.

  The sulfonic acid-based fullerene derivative and polyvinylimidazole were each uniformly dissolved in a methanol solution, and then the two solutions were mixed. Simultaneously with the mixing, an ionic complex is formed by the sulfonic acid-based fullerene derivative and polyvinylimidazole, so that it becomes insoluble in the methanol solution and a precipitate is formed. The precipitate was collected and vacuum-dried at 40 ° C. for 12 hours to immerse the ionic conductor according to the present invention in water or a methanol solution, but it did not dissolve even after one week.

  The ionic conductor obtained as described above was pressed in one direction so as to form a circular pellet having a diameter of 4 mm. As a result, although this powder did not contain any binder resin or the like, it was excellent in moldability and could be easily pelletized.

  Then, the conductivity was measured by the alternating current impedance method using this molded pellet. In the measurement, first, both sides of the pellet produced above were sandwiched between 4 mm diameter metal plates, an AC voltage (amplitude 100 mV) from 10 MHz to 1 Hz was applied thereto, and the complex impedance at each frequency was measured. In addition, the measurement was performed in two ways under a dry atmosphere and a humidified atmosphere.

  FIG. 13 is a Cole-Cole plot of a sample mixed at a ratio of sulfonic acid-based fullerene derivative: polyvinylimidazole = 6: 1 at 25 ° C. in a dry atmosphere.

  As is apparent from FIG. 13, a very clean single semicircular arc can be seen. This indicates that some charged particle conduction behavior exists inside the pellet. Furthermore, in the low frequency region, a rapid increase in the imaginary part of the impedance was observed. This indicates that blocking of charged particles occurs with the gold electrode as it gradually approaches the DC voltage. Naturally, the charged particles on the gold electrode side are electrons, so It can be seen that the particles are not electrons or holes but other charged particles, that is, ions (protons).

  This ionic conductivity can be obtained from the X-axis intercept of the arc seen on the high frequency side of the Cole-Cole plot of FIG. The temperature dependence of the ionic conductivity is shown in FIG. As is clear from FIG. 14, the ionic conductor according to the present invention showed high ionic conductivity in a wide temperature range even in a dry atmosphere, and the ionic conductivity increased with increasing temperature.

Next, the conductivity of the sample mixed at a ratio of sulfonic acid-based fullerene derivative: polyvinylimidazole = 4: 1 was measured by the alternating current impedance method, and the humidity dependency of the conductivity was measured. Specifically, both sides of the prepared pellet are sandwiched between 4 mm diameter metal plates, placed in a constant temperature and humidity chamber maintained at a predetermined humidity and 25 ° C., and an alternating voltage from 1 MHz to 1 Hz (amplitude 100 mV) is applied. The complex impedance at each frequency was measured. Since the complex impedance changed with time and was almost constant after 3 hours, the humidity was changed and measured after 4 hours. From the X-axis intercept of the arc seen on the high frequency side of the Cole-Cole plot, This ionic conductivity was determined. The results are shown in FIG. As is apparent from FIG. 15, the ionic conductivity increased with an increase in humidity, and a high ionic conductivity of 4.5 × 10 ⁻² (S / cm) was exhibited at a relative humidity of 95%.

Example 2
After mixing the monomer vinyl imidazole (VIm) and the fullerene methanophosphate (MPF), an attempt was made to polymerize by heating. The melting point of VIm is about 82 ° C., and the monomer is present as a liquid at high temperature, and the polymerization can be performed without adding a solvent or initiator separately for two reasons that the phosphate group can be an initiator for cationic polymerization. Tried. The mixture was mixed so that the ratio of VIm to phosphate group was 3: 1 and 9: 1 and kept at 100 ° C. for 16 hours. It was visually confirmed that when VIm was dissolved, it was mixed uniformly. After 16 hours, the mixture was allowed to cool to room temperature. When water was added to the obtained solid, it was confirmed that MPF was gradually dissolved in water, and although it was not completely insolubilized, it was found that it was considerably less soluble than single MPF.

  About the ionic conductor based on this invention obtained as mentioned above, the ionic conductivity was measured in the dry atmosphere at room temperature. The results are shown in FIG. As is clear from FIG. 16, the ionic conductivity decreases when VIm: phosphate group = 3: 1 and increases when 9: 1 compared to MPF alone. This result is presumed to be due to the difference in the amount of unreacted monomer remaining after polymerization. The more unreacted monomer remains, the higher ionic conductivity is likely. Furthermore, when the polymerization temperature was 150 ° C., insolubilization further progressed.

  As is clear from Example 1 and Example 2, the ionic conductor according to the present invention is a polymerization of the fullerene derivative as the derivative having the ion dissociable group and the substance having the basic group. Since an ion complex is formed with the formed compound, the fullerene derivative that was soluble in water or methanol solution can be insolubilized, and the proton conductivity is good even at low temperatures such as room temperature and in a dry state. Could be expressed. For this reason, if the ionic conductor according to the present invention is used as a proton exchange membrane, it is insoluble in water or methanol solution, so that an electrochemical device such as a fuel cell that is physically stable and can be started up when drying is used. Can be realized.

Example 3
In a mixed solution having a sulfonic acid-based fullerene derivative as shown in FIG. 12 and polyvinylimidazole as shown in FIG. 8 (p), a polyimide porous membrane (film thickness 30 μm, porosity 60%, average pore diameter 0.5 μm) Was immersed to fill the pores with the solution. Thereafter, the solvent was gradually removed to increase the solution concentration, and finally the solvent was completely removed to produce an ionic conductor according to the present invention. However, there is no problem even if the solvent remains in the polyimide porous membrane. The ionic conductor based on the present invention obtained as described above had good film formability and mechanical strength.

About the ion conductor produced as mentioned above, the conductivity was measured by the alternating current impedance method. In the measurement, first, both surfaces of the ion conductor prepared above are sandwiched between 4 mm diameter metal plates, and this is put in a constant temperature and humidity chamber maintained at a predetermined humidity and 25 ° C., and an AC voltage from 10 MHz to 1 Hz ( Amplitude 100 mV) was applied, the complex impedance at each frequency was measured, and the ionic conductivity was calculated. FIG. 17 is a Cole-Cole plot at 25 ° C. When the ionic conductivity was calculated from the Cole-Cole plot of FIG. 17, it was 6.8 × 10 ⁻⁴ Scm ⁻¹ at 30% relative humidity, 1.6 × 10 ⁻³ Scm ⁻¹ at 60% relative humidity, and relative The humidity was 5.2 × 10 ⁻³ Scm ⁻¹ at 95% humidity. As is apparent from the Cole-Cole plot in FIG. 17, as the humidity increases, the resistance value (intersection with the impedance (real part) Z ′) decreases and the ionic conductivity increases.

Example 4
In a solution having a sulfonic acid-based fullerene derivative as shown in FIG. 12, a vinyl imidazole as a polymer precursor (monomer) of the substance having the basic group, and an initiator, the same as in Example 3 The polyimide porous membrane was immersed, and the solution was filled in the pores. Then, it thermally polymerized and the solvent was removed and the ionic conductor based on this invention was produced. The ionic conductor based on the present invention obtained as described above had good film formability and mechanical strength.

About the ion conductor produced as mentioned above, the conductivity was measured by the alternating current impedance method. In the measurement, first, both sides of the ion conductor produced above are sandwiched between 4 mm diameter metal plates and placed in a constant temperature and humidity chamber maintained at a relative humidity of 60% and 25 ° C. AC voltage from 10 MHz to 1 Hz. (Amplitude 100 mV) was applied, the complex impedance at each frequency was measured, and the ionic conductivity was calculated. FIG. 18 is a Cole-Cole plot at 25 ° C. When the ionic conductivity was calculated from the Cole-Cole plot of FIG. 18, it was 1.6 × 10 ⁻³ Scm ⁻¹ at a relative humidity of 60%.

  While the present invention has been described with reference to the embodiments and examples, the above examples can be variously modified based on the technical idea of the present invention.

  For example, the example in which the derivative to which the ion dissociable group is bonded and the polymer of the substance having the basic group are mixed has been described above. In the carbon substance composed of at least one selected from the group consisting of the fullerene molecule, the cluster mainly composed of carbon, and the structure of linear or cylindrical carbon, the ion dissociable group and The basic group may be bonded.

  In addition, in the electrochemical device based on the present invention such as the fuel cell, the shape, configuration, material and the like can be appropriately selected without departing from the present invention.

Furthermore, the ion conductor based on this invention can be used for ion conduction of lithium ions other than the above-mentioned proton (H ⁺ ), and can be applied to alkaline secondary batteries and the like.

1 is a schematic diagram of an ionic conductor according to the present invention, according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing fullerene molecules serving as a base in the ion conductor of the present invention. FIG. 4 is a schematic diagram showing various examples of carbon clusters that are the base in the ion conductor of the present invention. It is a schematic diagram which shows the other example (partial fullerene structure) of a carbon cluster equally. It is a schematic diagram which shows the other example (diamond structure) of a carbon cluster similarly. It is a schematic diagram which shows the other example (what cluster has couple | bonded) of the carbon cluster similarly. FIG. 2 is a schematic view of carbon nanotubes and carbon fibers serving as a matrix of the ion conductor of the present invention. It is the structural formula of the material that can be used as the polymer of the substance having the basic group. FIG. 2 is a structural formula of an example of the polymer of the substance having the basic group. FIG. 2 is a schematic diagram showing the proton conduction mechanism of the fuel cell. It is a schematic sectional drawing which shows an example of a fuel cell. It is a schematic diagram of a sulfonic acid-based fullerene derivative as the derivative used in Example 1 according to an example of the present invention. It is a graph which shows the measurement result of the complex impedance of the ion conductor based on this invention similarly. It is a graph which shows the measurement result of the ionic conductivity of the ion conductor based on this invention similarly. It is a graph which shows the humidity dependence of the ionic conductivity of the ionic conductor based on this invention similarly. It is a graph which shows the temperature dependence of the ionic conduction of the ionic conductor based on this invention similarly. It is a graph which shows the measurement result of the complex impedance of the ion conductor based on this invention similarly. It is a graph which shows the measurement result of the complex impedance of the ion conductor based on this invention similarly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ion conductor (proton conduction part), 2 ... 1st pole (negative electrode), 2a ... Catalyst,
3 ... 2nd pole (positive electrode), 3a ... Catalyst, 8, 9 ... Terminal, 12 ... Inlet (for hydrogen),
13 ... outlet (for hydrogen), 14 ... Fuel (H _2), 15 ... flow path (for hydrogen),
16 ... Inlet (for oxygen), 17 ... Channel (for oxygen), 18 ... Outlet (for oxygen),
19 ... Oxygen (air)

Claims (11)

A derivative in which an ion dissociable group represented by the following structural formula is bonded directly or indirectly to a carbon material composed of a fullerene molecule; a polymer composed of polyvinyl imidazole having a basic group; and a porosity as a binder and a polymer material quality; was containing organic, the derivative and the polymer that is held in the pores of the polymeric material of the porous, ion conductor.
Ion dissociable groups:
_{-SO 3 M, -PO (OM)} 2, -SO 2 NMSO 2 -, - SO 2 NM 2, -COOM, = CPO (OM) 2 , and _{= C (SO 3 M) 2} ( where, M is a cation At least one selected from the group consisting of:   The ion conductor according to claim 1, wherein the derivative having the ion dissociable group bonded thereto and the polymer having the basic group are mixed.   The ionic conductor according to claim 1, wherein at least one of the ion dissociable groups is an acidic functional group.   2. The ionic conductor according to claim 1, wherein a ratio of the ion dissociable group to the basic group (the basic group / the ion dissociable group) is 20 or less in terms of a molar ratio. And a functional group having at least the ionic dissociative group is bonded to the carbon material, the functional group _{-A-SO 3 M, -A-} PO (OM) 2, -A-SO 2 NMSO 2 -R ⁰ , -A-SO ₂ NM ₂ and -A-COOM [where A is -O-, -R-, -O-R-, -R-O-, -O-R-O- or -R- O—R′— (R and R ′ may be the same or different from each other, and are represented by CxHy or CxFyHz (1 ≦ x ≦ 20, 1 ≦ y ≦ 40, 0 ≦ z ≦ 39). An alkyl moiety or a fluorinated alkyl moiety), M is a group that becomes a cation, and R ⁰ is —CF ₃ or —CH ₃ . The ionic conductor according to claim 1, which is at least one selected from the group consisting of: The ionic conductor according to claim 1 , wherein the porous polymer material is a polyimide. And wherein said derivative of said carbon material according to claim 1, and said polymer of claim 1 is dissolved in a solvent, to the resulting solution, by immersing the porous body of polymeric material serving as the binder The method for producing an ionic conductor , wherein the solution is filled in the pores of the porous body, and then the solvent is removed. The derivative of the carbon substance according to claim 1 and the vinylimidazole having the basic group according to claim 1 are dissolved in a solvent, and the obtained solution is made of a polymer material that becomes the binder. The porous body is immersed, the solution is filled in the pores of the porous body, and then the vinylimidazole is polymerized to form the polymer according to claim 1, and further the solvent is removed . The manufacturing method of an ion conductor. The method for producing an ionic conductor according to claim 7 or 8, wherein the ionic conductor according to any one of claims 2 to 6 is produced. An electrochemical device in which the ion conductor according to any one of claims 1 to 6 is sandwiched between a first electrode and a second electrode. The electrochemical device according to claim 10 configured as a fuel cell.

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