JP4840640B2 - Ionic conductor and energy device using the same - Google Patents

Description

  The present invention relates to an ionic conductor and an energy device using the same, and more particularly to an ionic conductor containing a polar substance, a cation component, and an anion component, and an energy device using the ionic conductor, particularly a fuel cell.

Conventionally, it has been proposed to apply an electrolyte containing a room temperature molten salt to a fuel cell.
Specifically, a proton conductor using a room temperature molten salt is applied, and one based on a non-humidifying operation has been proposed (see Patent Document 1).
Moreover, what applied the normal temperature molten salt which consists of a hydrophobic anion and a hydrophobic cation, and the thing which prevents mixing of the water to normal temperature molten salt is proposed (refer patent document 2).
JP 2003-123791 A Special table 2003-535450 gazette

  However, the ambient temperature molten salt electrolyte applied to the fuel cells described in Patent Document 1 and Patent Document 2 is assumed to be used without containing water. Has been reported to worsen.

  On the other hand, the present inventors have conducted research on these, and as a result, for example, by adding water to a hydrophilic ambient temperature molten salt, proton conductivity is improved, and performance as a fuel cell (for example, IV characteristics) is improved. New technical knowledge was obtained.

  The present invention has been made on the basis of such technical knowledge, and an object of the present invention is to provide an ion conductor capable of improving proton conductivity, and an energy device using the same, particularly a fuel cell. There is.

  As a result of further research on the above technical knowledge, the present inventors have found that the above object can be achieved by the coexistence of a polar substance, a cation component, and an anion component, and have completed the present invention.

That is, the ionic conductor of the present invention contains a room temperature molten salt composed of 1,2-diethyl-3-methyl-imidazolium cation and boron tetrafluoride anion, and water .

The energy device of the present invention uses the ionic conductor of the present invention.
Furthermore, a fuel cell can be mentioned as an example of the energy device of the present invention.

  According to the present invention, since a polar substance, a cation component, and an anion component are allowed to coexist, an ion conductor capable of improving proton conductivity, and an energy device using the same, particularly a fuel cell can be provided. .

Hereinafter, the ion conductor of the present invention will be described in detail.
As described above, the ionic conductor of the present invention contains a polar substance, a cation component, and an anion component.
With such a configuration, proton conductivity can be improved.

In the present invention, it is desirable that all or part of the cation component is a molecular cation and all or part of the anion component is a molecular anion.
By adopting such a configuration, it becomes possible to form a complex ion or the like with a polar substance, and proton conductivity can be further improved.
In particular, it is more desirable that all of the cation components are molecular cations and that all of the anion components are molecular anions from the viewpoint of easy formation of a polar substance and complex ions.
“Molecular cation” and “molecular anion” mean a polyatomic cation and a polyatomic anion, respectively.

Furthermore, in this invention, it is desirable to contain the normal temperature molten salt which contains a molecular cation and a molecular anion, and these form.
By containing such a room temperature molten salt, it has properties as a room temperature molten salt, and further has high ionic conductivity, whereby proton conductivity can be further improved.
On the other hand, if it is a room temperature molten salt, it is not necessary that both the cation component and the anion component to be formed are a molecular cation and a molecular anion, respectively.
Here, “room temperature molten salt” refers to a salt that melts at room temperature and does not evaporate at a high temperature and is a stable medium with high polarity and specific heat.
A typical example of such a room temperature molten salt is a Bronsted acid-base type. Details will be described later.

In the present invention, the molecular cation preferably has at least one heteroatom.
Such a molecular cation containing a heteroatom has high ionic conductivity and can further improve proton conductivity.

  In addition, a hetero atom is an atom other than a carbon atom (C) and a hydrogen atom (H), and typically an oxygen atom (O), a nitrogen atom (N), a sulfur atom (S), a phosphorus atom (P ), Fluorine atom (F), chlorine atom (Cl), bromine atom (Br), iodine atom (I), boron atom (B), cobalt atom (Co), antimony atom (Sb), and the like. .

Furthermore, in the present invention, it is desirable that all or part of the room temperature molten salt is a hydrophilic room temperature molten salt.
Such room temperature molten salt can improve the water retention ability in the ionic conductor when water is contained as a polar substance, which will be described in detail later, and can further improve the proton conductivity. It becomes possible.

Here, the cation component and the anion component used in the ion conductor of the present invention will be described in detail with specific examples.
In the present invention, the following cation component and anion component can be used in appropriate combination.

  Examples of the molecular cation which is a kind of the cation component include, for example, an imidazolium derivative cation, more specifically, a monosubstituted imidazolium derivative cation represented by the following formula (1):

(Wherein R ₁₁ represents a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably an alkyl group having 1 to 20 carbon atoms or an arylalkyl group).

  Specific examples of the hydrocarbon group include a methyl group and a butyl group.

  In addition, a disubstituted imidazolium derivative cation represented by the following formula (2) (Distributed Imidazol Derivatives Cation);

(In the formula, R ₂₁ and R ₂₂ may be the same or different and each represents a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably an alkyl group having 1 to 20 carbon atoms or an arylalkyl group. .).

Examples of R ₂₁ and R ₂₂ include any combination of the same groups as those described above for R _11, and in addition, ethyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group , Tetradecyl group, hexadecyl group, octadecyl group, benzyl group, γ-phenylpropyl group, and the like.

As specific examples of typical combinations of these groups, R ₂₁ is a methyl group, and R ₂₂ is a methyl group, ethyl group, butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group. , Tetradecyl group, hexadecyl group, octadecyl group, benzyl group, and γ-phenylpropyl group, and those in which R ₂₁ is an ethyl group and R ₂₂ is a butyl group.

  Furthermore, a trisubstituted imidazolium derivative cation represented by the following formula (3) (Tristubulated Imidazol Derivatives Cation);

(In the formula, R _{31 to} R ₃₃ may be the same or different and each represents a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably an alkyl group having 1 to 20 carbon atoms or an arylalkyl group. .).

Then, as the R ₃₁ to R _33, there may be mentioned those obtained by arbitrarily combining the same as R ₁₁ mentioned above, other ethyl group, a propyl group, a hexyl group, and the like hexadecyl .

Specific examples of typical combinations of these groups include those in which R ₃₁ is an ethyl group, R ₃₂ and R ₃₃ are methyl groups, R ₃₁ is a propyl group, and R ₃₂ and R ₃₃ are A methyl group, R ₃₁ is a butyl group, R ₃₂ and R ₃₃ are methyl groups, R ₃₁ is a hexyl group, R ₃₂ and R ₃₃ are methyl groups, R ₃₁ is hexadecyl And a group in which R ₃₂ and R ₃₃ are methyl groups.

  Moreover, the pyridinium derivative cation (Pyridinium Derivatives Cation) represented by following formula (4);

(In the formula, R _{41 to} R ₄₄ may be the same or different, and are hydrogen or a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably a C 1-20 alkyl group or arylalkyl group. Can be included).

Then, as the R ₄₁ to R _44, there may be mentioned those obtained by arbitrarily combining the same as R ₁₁ mentioned above, other hydrogen, ethyl group, hexyl group, and octyl group.

Specific examples of typical combinations of these groups include those in which R ₄₁ is an ethyl group, R _{42 to} R ₄₄ are hydrogen, R ₄₁ is a butyl group, and R _{42 to} R ₄₄ are hydrogen. R ₄₂ and R ₄₃ are hydrogen and R ₄₄ is a methyl group, R ₄₂ and R ₄₄ are hydrogen and R ₄₃ is a methyl group, R ₄₂ and R ₄₃ are methyl groups R ₄₄ is hydrogen, R ₄₂ and R ₄₄ are methyl and R ₄₃ is hydrogen, R ₄₂ and R ₄₃ are hydrogen and R ₄₄ is ethyl, R ₄₁ is hexyl R _{42 to} R ₄₄ are hydrogen, R ₄₂ and R ₄₃ are hydrogen and R ₄₄ is a methyl group, R ₄₂ and R ₄₄ are hydrogen and R ₄₃ is a methyl group, R ₄₁ is an octyl group, _{R 4} Those to R ₄₄ are those or hydrogen _{R 42} and _{R 43} are hydrogen _{R 44} is a methyl _group, an _{R 42} and _{R 44} are hydrogen _{R 43} can be exemplified such as a methyl group .

  Further, a pyrrolidinium derivative cation represented by the following formula (5) (Pyrrolidinium Derivatives Cation);

(In the formula, R ₅₁ and R ₅₂ may be the same or different and each represents a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably an alkyl group having 1 to 20 carbon atoms or an arylalkyl group. .).

Examples of R ₅₁ and R ₅₂ include those obtained by arbitrarily combining the same as R ₁₁ described above, and other examples include an ethyl group, a propyl group, a hexyl group, and an octyl group. .

Specific examples of typical combinations of these groups include those in which R ₅₁ is a methyl group, R ₅₂ is a methyl group, an ethyl group, a butyl group, or a hexyl group. , An octyl group, R ₅₁ is an ethyl group, R ₅₂ is a butyl group, and R ₅₁ and R ₅₂ are a propyl group, a butyl group, and a hexyl group.

  Moreover, the ammonium derivative cation (Ammonium Derivatives Cation) represented by following formula (6);

(In the formula, R _{61 to} R ₆₄ may be the same or different and each represents a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably an alkyl group having 1 to 20 carbon atoms or an arylalkyl group. .).

Then, as the R ₆₁ to R _64, there may be mentioned those obtained by arbitrarily combining the same as R ₁₁ mentioned above, other ethyl group, and octyl group.

Specific examples of typical combinations of these groups include those in which R _{61 to} R ₆₄ are a methyl group, an ethyl group, a butyl group, R ₆₁ is a methyl group, and R ₆₂ to R ₆₄ can be exemplified such as an octyl group.

  Furthermore, a phosphonium derivative cation represented by the following formula (7) (Phosphonium Derivatives Cation);

(In the formula, R _{71 to} R ₇₄ may be the same or different and each represents a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably an alkyl group having 1 to 20 carbon atoms or an arylalkyl group. .).

Then, as the R ₇₁ to R _74, there may be mentioned those obtained by combining arbitrarily the same as R ₁₁ mentioned above, other ethyl group, an isobutyl group, a hexyl group, an octyl group, a tetradecyl group, a hexadecyl group , Phenyl group, benzyl group and the like.

As specific examples of typical combinations of these groups, R ₇₁ is a methyl group, R _{72 to} R ₇₄ are butyl groups or isobutyl groups, R ₇₁ is an ethyl group, R _{72 to} R ₇₄ are butyl groups, R _{71 to} R ₇₄ are butyl groups or octyl groups, R ₇₁ is a tetradecyl group, and R _{72 to} R ₇₄ are butyl groups, Examples thereof include a hexyl group, R ₇₁ is a hexadecyl group, R _{72 to} R ₇₄ are butyl groups, R ₇₁ is a benzyl group, and R _{72 to} R ₇₄ are phenyl groups. it can.

  Further, a guanidinium derivative cation represented by the following formula (8) (Guanidinium Derivatives Cation);

(In the formula, R _{81 to} R ₈₆ may be the same or different, and are hydrogen or a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably a C 1-20 alkyl group or arylalkyl group. Can be included).

Then, as the R ₈₁ to R _86, there may be mentioned those obtained by arbitrarily combining the same as R ₁₁ mentioned above, other hydrogen, ethyl, propyl, and the like isopropyl group.

Specific examples of typical combinations of these groups include those in which all of R _{81 to} R ₈₆ are hydrogen or a methyl group, R ₈₁ is an ethyl group, and R _{82 to} R ₈₅ are methyl groups. R ₈₆ is hydrogen, R ₈₁ is isopropyl, R _{82 to} R ₈₅ are methyl, R ₈₆ is hydrogen, R ₈₁ is propyl, R _{82 to} R ₈₆ are methyl, etc. Can be mentioned.

  Furthermore, an isouronium derivative cation (Isouronium Derivatives Cation) represented by the following formula (9);

(In the formula, R _{91 to} R ₉₅ may be the same or different, and are hydrogen or a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably a C 1-20 alkyl group or arylalkyl group. And A ₉ represents an oxygen atom or a sulfur atom.).

Then, as the R ₉₁ to R _95, there may be mentioned those obtained by arbitrarily combining the same as R ₁₁ mentioned above, other hydrogen, and the like ethyl.

Specific examples of typical combinations of these groups include those in which A ₉ is an oxygen atom (O) and all of R _{91 to} R ₉₅ are methyl groups, R ₉₁ is an ethyl group, R ₉₂ those to R ₉₅ is a methyl group, _{a 9} is a sulfur atom _(S), and the like as _{R 91} is an ethyl _group, R 92 _{to R 95} is a methyl group.

On the other hand, as the molecular anion, for example, a sulfate anion [SO ₄ ²⁻ ], a hydrogen sulfate anion [HSO ₄ ⁻ ] or a sulfate ester anion (Sulfates anion) represented by the following formula (10);

(Wherein R ₁₀₁ represents a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably an alkyl group having 1 to 20 carbon atoms or an arylalkyl group).

Then, as R ₁₀₁ may include the same as R ₁₁ mentioned above, other ethyl group, a hexyl group, and octyl group.

Further, typical examples include those in which R ₁₀₁ is a methyl group, an ethyl group, a butyl group, a hexyl group, or an octyl group.

  Moreover, the sulfonate ester anion (Sulfonates anion) represented by following formula (11);

(Wherein R ₁₁₁ represents a monovalent organic group, preferably a monovalent hydrocarbon group, more preferably an alkyl group or arylalkyl group having 1 to 20 carbon atoms, and further a fluorine-substituted product thereof). be able to.

As typical examples, R ₁₁₁ is a fluorine-substituted methyl group (corresponding to a trifluoromethanesulfonate anion), and further a p-tolyl group (corresponding to a p-toluenesulfonic acid anion). Some can be mentioned.

  Further, an amide anion or an imide anion represented by the following formulas (12) to (14);

Can be mentioned.
The amide anion and imide anion are not necessarily limited to these.

  In addition, a methane anion represented by the following formula (15) or (16);

Can be mentioned.
The methane anion is not necessarily limited to these.

  In addition, boron-containing compound anions represented by the following formulas (17) to (23);

Can be mentioned.
Note that the boron-containing compound anion is not necessarily limited thereto.

  Furthermore, phosphorus-containing compound anions represented by the following formulas (24) to (32);

Can be mentioned.
The phosphorus-containing compound anion is not necessarily limited to these.

  And a carboxylate anion represented by the following formula (33) or (34):

Can be mentioned.
The carboxylate anion is not necessarily limited to these.

  And a metal element-containing anion represented by the following formula (35) or (36):

Can be mentioned.
The metal element-containing anion is not necessarily limited to these.

On the other hand, although not a molecular anion, as other anion components, a halide anion (halogenides anion) fluorine anion [F ⁻ ], chlorine anion [Cl ⁻ ], bromine anion [Br ⁻ ], iodine anion [I ⁻ ] Can also be mentioned.

Furthermore, in the present invention, a mixture of an imidazolium derivative cation, a pyridinium derivative cation, a pyrrolidinium derivative cation or an ammonium derivative cation, and a molecular cation according to any combination thereof, a boron tetrafluoride anion, a trifluoromethanesulfone, Nate anion, hydrogen fluoride anion [(HF _n ) F ⁻ (n is preferably a real number of 1 to 3)], monohydrogen sulfate anion or dihydrogen phosphate anion, and molecular properties related to any combination thereof It preferably comprises a mixture of anions.
This is because a combination of these molecular cations and molecular anions is a room temperature molten salt and exhibits good hydrophilicity.

  In the present invention, the polar substance to be used preferably functions as a polar solvent. In an electrically neutral substance, the arrangement of positive and negative charges is biased. In particular, positive and negative charges are present at both ends. It is desirable to be a compound having a structure like a wrinkle.

As such an index of polarity, polarity value, dipole moment, dielectric constant, hydrogen bondability, solubility parameter, etc. can be applied.
For example, the polar substance preferably has a polarity value greater than 30, more preferably greater than 40, and even more preferably greater than 50. When the polarity value is less than 30, the polarity is insufficient and it is difficult to obtain a sufficient function as a solvent.

  Table 1 shows solubility parameters (δ) and polarity values (Et) of typical substances. Table 1 is an excerpt from “New Experimental Chemistry Course”, author name: The Chemical Society of Japan, publisher: Maruzen Co., Ltd.

The solubility parameter in the table is the following (Equation 1).
δ = (E / V) ^1/2 (Formula 1)
(E in the formula is calculated from the cohesive energy of liquid molecules and V is the molecular volume.) The larger the value, the higher the solubility.
In the table

Furthermore, in the present invention, polar substances include water, methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, butylene glycol, acetone, acetonitrile, dimethyl sulfoxide, dimethylformamide, pyridine, α-picoline, methyl acetate, acetic acid. Polar substances relating to ethyl, propyl acetate, butyl acetate, acetic acid, ethylene oxide, polyethylene oxide or polypropylene oxide, and any combination thereof can be mixed and used suitably.
As the polar substance, a substance having a large molecular weight such as polyethylene glycol or polypropylene glycol can be used.
When such a high molecular weight polar substance is contained, it is desirable to add dimethyl sulfoxide, dimethylformamide, or the like.
In particular, water or the like can be more suitably used from the viewpoint of high polarity and solubility.

Moreover, in the ion conductor of this invention, it does not specifically limit as the manufacturing method, It can produce by a conventionally well-known method.
When mixing room temperature molten salt and water, which is an example of a polar substance, in the case of a highly viscous room temperature molten salt, for example, warm the temperature to about 50 to 80 ° C. and mix both to mix uniformly. It is possible to improve the proton conductivity by coexistence of both.

In addition, what is necessary is just to set the mixing ratio in this case as normal temperature molten salt and water by molar ratio (normal temperature molten salt: water) 100: 1-1: 5.
By setting it as such a value, the improvement effect of proton conductivity can be exhibited further.

  The production method of the room temperature molten salt to be used is not particularly limited, but can be produced by, for example, a conventionally known neutralization method.

Next, the energy device of the present invention will be described in detail.
As described above, the energy device of the present invention uses the ionic conductor of the present invention. The form can be appropriately adjusted according to the mode of use.
More specifically, an ion conductor as described above can be applied to a fuel cell, a secondary battery, a capacitor, or the like.

The fuel cell is a device that can directly convert the chemical energy of the fuel into electric energy and can be expected to have high energy conversion efficiency.
When the ion conductor of the present invention is applied as an electrolyte to a single cell of a fuel cell, it is possible to adjust the proton transmission field and the affinity at the three-phase interface, and to improve the IV characteristics.

In addition, the above-described ionic conductor exhibits excellent thermal stability (non-volatile, zero vapor pressure, liquid in a wide temperature range), high ion density, large heat capacity, and the like, so that the intermediate temperature range (120 Operation at about ℃).
In a system incorporating such a fuel cell, the radiator load can be reduced compared to a conventional polymer electrolyte fuel cell, and the size of the radiator can be reduced.
As a result, the system volume can be reduced, and the weight of the system can be reduced.

  Furthermore, by applying the ion conductor of the present invention to a secondary battery, particularly a lithium battery, the non-volatile and non-flammable properties are effective, and the battery can be endured to be enlarged or used at a relatively high temperature. It becomes possible.

  Furthermore, when applied to a capacitor, the same effect as that of a secondary battery can be obtained.

Here, as an example of the energy device of the present invention, a case where an ion conductor is applied to a fuel cell will be described with reference to the drawings.
FIG. 1 is an explanatory diagram showing a configuration of a fuel cell which is an example of an energy device.
As shown in the figure, a pair of electrodes 20 that face each other with an ion conductor 10 functioning as an electrolyte in between are provided. The electrode 20 includes a catalyst layer 22 and a gas diffusion layer 24.

In addition, a pair of separators 30 that are opposed to each other are provided.
Thus, the gas flow path 26 is formed in each electrode 20 by the separator 30, and hydrogen (or a fuel gas containing hydrogen) and oxygen (or an oxidizing gas containing oxygen) are supplied. ing.
Note that the electrode 20 has an anode on the side supplied with the fuel gas and a cathode on the side supplied with the oxidizing gas.

When power is generated by this fuel cell, each gas is supplied from the gas flow path 26 to the catalyst layer 22 through the gas diffusion layer 24, and the following electrochemical reaction proceeds.
H ₂ → 2H ⁺ + 2e ⁻ (Formula 2)
2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (Formula 3)
H ₂ + (1/2) O ₂ → H ₂ O (Formula 4)

(Equation 2) shows the reaction on the cathode side of the fuel cell.
(Equation 3) shows the reaction on the anode side of the fuel cell.
(Equation 4) is a reaction performed in the entire fuel cell.

  Hereinafter, the present invention will be described in more detail with reference to some examples and comparative examples, but the present invention is not limited to such examples.

Example 1
Room temperature molten salt (2 EtEMImBF ₄ ) composed of 1,2-diethyl-3-methyl-imidazolium cation, which is a kind of imidazolium trisubstituted derivative cation, and boron tetrafluoride anion, which is a kind of boron-containing compound anion, and polarity Water, which is an example of the substance, was mixed at a molar ratio of room temperature molten salt: water = 1: 1 to obtain an ionic conductor of this example.

(Comparative Example 1)
Except that water was not mixed, the same operation as in Example 1 was repeated to obtain an ion conductor of this example.

[Performance evaluation]
Using the ionic conductors of the above examples, a power generation apparatus simulating a fuel cell was produced. FIG. 2 is an explanatory diagram illustrating a configuration of the power generation device.
Specifically, the ion conductor 10 was held between the electrodes 20 made of carbon paper coated with a catalyst metal such as platinum.
Then, hydrogen was supplied from the back surface of one electrode 10 and oxygen (air) was supplied from the back surface of the other electrode 10 to evaluate the power generation performance (IV characteristics).
FIG. 3 shows the power generation performance (relationship between current and voltage), which is the obtained result.

  From FIG. 3, compared with the case of Comparative Example 1 (only room temperature molten salt) indicated by a broken line, the case of Example 1 (mixed room temperature molten salt and polar substance (water)) indicated by a solid line is It can be seen that the IV characteristics are excellent.

It is explanatory drawing which shows the structure of a fuel cell. It is explanatory drawing which shows the structure of the electric power generating apparatus which imitated the fuel cell. It is a graph which shows the electric power generation performance of Example 1 and Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ion conductor 20 Electrode 22 Catalyst layer 24 Gas diffusion layer 26 Gas flow path 30 Separator

Claims (3)

An ionic conductor comprising a room temperature molten salt composed of a 1,2-diethyl-3-methyl-imidazolium cation and a boron tetrafluoride anion, and water . An energy device using the ionic conductor according to claim 1 . A fuel cell using the ionic conductor according to claim 1 .

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