Electrolyte materials and electrolyte membranes

Abstract

This invention provides non-fluorine-based electrolyte materials and electrolyte membranes that exhibit excellent mechanical strength and ionic conductivity. [Solution] The electrolyte material according to the present invention is a non-fluorinated electrolyte material consisting of a carbon chain skeleton (alkane or benzene ring) having 1 to 11 carbon atoms, which includes an electron-withdrawing functional group and an ion-exchange group. Furthermore, the electrolyte membrane (1) according to the present invention has a porous substrate (20) and particles (10) formed by bonding the non-fluorinated electrolyte material to an inorganic substance, which are applied to the porous substrate, specifically, for example, filling the pores (21) of the porous substrate 20.

Description

Technical Field

[0001] The present invention relates to electrolyte materials and electrolyte membranes for fuel cells and electrolyzers having solid electrolytes.

Background Art

[0002] A fuel cell is an electrochemical device that converts chemical energy into electrical energy through the electrochemical reaction of hydrogen as fuel and oxygen in the air, and extracts electricity. Compared with conventional batteries, it has the advantage of high energy conversion efficiency and is used in various fields. The basic configuration of a fuel cell consists of an anode and a cathode, and an electrolyte membrane as a partition between the anode and the cathode. Fuel cells are classified into alkaline electrolyte fuel cells, solid polymer fuel cells, phosphoric acid fuel cells, etc., depending on the state and type of the electrolyte membrane. Among them, the solid polymer fuel cell has a shorter startup time and a lower operating temperature of 80°C to 100°C compared to other fuel cells, and is expected to be used as a power source for portable devices and vehicles.

[0003] In a solid polymer fuel cell, generally, an electrolyte membrane formed from an electrolyte material in which an ion exchange group is bonded to an organic polymer compound is used, and Nafion (registered trademark) of DuPont is cited as a typical electrolyte material. Nafion is composed of a polymer of perfluorosulfonic acid having a hydrophobic skeleton composed of carbon-fluorine (C-F) bonds and a perfluoro side chain having a sulfonic acid group. Due to the strong hydrophobicity of the C-F bond, it phase-separates from the hydrophilic sulfonic acid group, and a nanochannel in which protons are easily conducted is formed by the aggregated sulfonic acid groups. Due to such properties, electrolyte materials having C-F bonds have high ionic conductivity. Also, since fluorine has the highest electronegativity among all elements, it can stabilize the negative charge generated by the proton release of the ion exchange group and increase the ionic conductivity. Due to these features, not only Nafion, but in solid polymer fuel cells and electrolyzers, electrolyte materials composed of organic fluorine compounds containing C-F bonds in the skeleton part are widely used.

[0004] In recent years, several compounds belonging to the organic fluorine group, particularly those known as PFAS (Per and poly FluoroAlkyl Substances), have been identified as harmful to humans and other organisms. Moreover, because PFAS are highly persistent and bioaccumulative, there is a growing movement in various countries to ban or restrict their use and manufacture. The Stockholm Convention on Persistent Organic Pollutants (the so-called POPs Convention) already prohibits or restricts the use and manufacture of PFAS.

[0005] Therefore, in the development of electrolyte materials used in fuel cells, progress is being made in the development of electrolyte materials composed of fluorine-free organic compounds (non-fluorinated organic compounds). Non-fluorinated organic compounds, naturally, do not contain CF bonds in their main chain skeleton. Following the example of phase separation in fluorinated organic compounds, research has been conducted to achieve phase separation in non-fluorinated organic compounds, but a satisfactory level has not yet been reached. On the other hand, efforts have also been made to increase the ion exchange capacity in order to improve the ionic conductivity of fluorinated organic compounds. However, it has been pointed out that increasing the ion exchange capacity leads to significant water swelling of the electrolyte and a decrease in mechanical strength. For this reason, in the development of electrolyte materials composed of non-fluorinated organic compounds, the focus is usually on developing methods that increase the ion exchange capacity without reducing mechanical strength.

[0006] For example, Patent Document 1 describes an electrolyte membrane using a polyarylene polymer as the electrolyte material. In Patent Document 1, in order to obtain an electrolyte membrane with excellent mechanical strength, the above polyarylene polymer is used as a pore-filling membrane in which the pores of a porous substrate are filled. This polyarylene polymer has a structure in which two or more structural units are linked together, each unit consisting of a first group in which an aromatic group or aromatic ring having an ion exchange group is linked via a single bond, and a second group in which two or more aromatic rings without an ion exchange group are linked via a single bond or spiro atom. From the viewpoint of chemical durability of the pore-filling membrane and ease of filling into the pores, the weight-average molecular weight of the above polyarylene polymer is preferably 30,000 or more, and more preferably 100,000 or more.

[0007] Furthermore, for example, Patent Document 2 describes a method for increasing the mechanical strength of an electrolyte membrane by crosslinking the electrolyte material by active energy ray irradiation. This electrolyte membrane is formed by mixing a crosslinkable aromatic polymer electrolyte with a polymerizable monomer having ionic groups and a crosslinking agent without ionic groups in an appropriate composition ratio, filling the pores of a hydrophobic porous substrate with the mixture, and then forming a crosslinked structure by active energy ray irradiation. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. WO2023 / 223990 [Patent Document 2] Japanese Patent Publication No. 2016-207610 [Overview of the project] [Problems that the invention aims to solve]

[0009] In Patent Document 1, from the viewpoint of ease of filling a porous substrate with polyarylene polymer, it is preferable that the ion exchange group of the first group be bonded to the aromatic ring constituting the main chain of the polymer via a linking group having 6 or more carbon atoms. However, this has the problem that the ion exchange capacity cannot be sufficiently increased and the ionic conductivity is low. In addition, because there is a second group without an ion exchange group bonded to the first group with an ion exchange group on either side, the ion exchange capacity cannot be sufficiently increased and the ionic conductivity is low.

[0010] Patent Document 2 states that optimizing the composition ratio of a crosslinkable aromatic polymer electrolyte, a polymerizable monomer having an ionic group, and a crosslinking agent without an ionic group is important. However, unreacted monomers remaining after irradiation with active energy rays hinder ion conduction in the electrolyte. In addition, these unreacted monomers precipitate on the electrolyte surface over time, hindering ion conduction near the surface, resulting in a problem of low ionic conductivity.

[0011] The problem that this invention aims to solve is to provide a non-fluorine-based electrolyte material and electrolyte membrane that have excellent ionic conductivity without reducing mechanical strength. [Means for solving the problem]

[0012] The non-fluorine-based electrolyte material according to the present invention, which was developed to solve the above problems, It consists of a carbon chain skeleton with 1 to 11 carbon atoms, containing an electron-withdrawing functional group and an ion-exchange group.

[0013] The inventors of this invention diligently investigated methods to increase the ionic conductivity of non-fluorinated organic compounds and, as a result, discovered a method to realize electrolyte materials with high ionic conductivity by introducing electron-withdrawing groups, leading to the present invention. While the improvement of acid dissociation degree by using electron-withdrawing groups is a widely known phenomenon, there are many unknown aspects to the technology of enhancing the ionic conductivity of non-fluorinated organic compounds with electron-withdrawing groups other than fluorine. The inventors of this invention have investigated electron-withdrawing groups other than fluorine in detail and clarified their applicability to electrolyte materials.

[0014] Furthermore, regarding the improvement of ionic conductivity in electrolyte membranes made of non-fluorinated organic compounds, conventional techniques that relied on ion exchange capacity made it difficult to balance ionic conductivity and mechanical strength. However, in the present invention, by improving the quality of the ion exchange groups, it is possible to achieve high ionic conductivity without increasing the ion exchange capacity. By keeping the ion exchange capacity below a predetermined amount, it is possible to maintain high mechanical strength when used as an electrolyte membrane.

[0015] In the non-fluorinated electrolyte material according to the present invention, the carbon chain skeleton having 1 to 11 carbon atoms may be a linear structure, a branched structure, or a cyclic structure. Typical examples of the carbon skeleton include alkanes or benzene rings. Since the carbon chain skeleton has 1 to 11 carbon atoms and has a smaller molecular weight compared to conventional non-fluorinated electrolyte materials, the amount of ion exchange groups introduced per unit mass can be increased. Furthermore, the electrolyte material according to the present invention contains an electron-withdrawing functional group. The electron-withdrawing functional group attracts the negative charge that accumulates on the ion exchange group, thereby weakening the localization of the negative charge and stabilizing the molecule, which in turn increases the degree of acid dissociation of the ion exchange group (reduces the pKa). As a result, an electrolyte material with excellent ionic conductivity can be obtained even with a fluorine-free structure.

[0016] In the above-mentioned non-fluorinated electrolyte material, the ion exchange group is preferably one of a sulfonic acid group (-SO3H), a phosphate group (-H2PO4), a phosphonic acid group (-H2PO3), or a carboxylic acid group (-COOH). By introducing these acidic groups as ion exchange groups into the carbon chain skeleton, proton conductivity can be imparted to the electrolyte material.

[0017] Furthermore, examples of electron-withdrawing functional groups include chloro groups, bromo groups, iodine groups, nitro groups (-NO2), cyano groups (-CN), sulfonic acid groups, phosphate groups, phosphonic acid groups, or carboxylic acid groups. Here, sulfonic acid groups, phosphate groups, phosphonic acid groups, and carboxylic acid groups are both ion-exchange groups and electron-withdrawing groups. In other words, the electron-withdrawing functional groups may perform only the role of electron withdrawal, or they may perform both the role of electron withdrawal and ion exchange simultaneously.

[0018] Furthermore, the carbon chain skeleton preferably includes a saturated carbon chain skeleton with 1 to 8 carbon atoms or an aromatic hydrocarbon. Examples of such carbon chain skeletons include alkylene, phenylene, and xylylene. Furthermore, it is preferable that the carbon chain skeleton is a saturated carbon chain skeleton having 1 to 4 carbon atoms. By using the above-described structure for the carbon chain skeleton, the ionic conductivity of the electrolyte material can be increased.

[0019] The electrolyte membrane according to the present invention can be formed from the above-mentioned non-fluorinated electrolyte material. Furthermore, the electrolyte membrane according to the present invention may have a porous substrate and the non-fluorine-based electrolyte material applied to the porous substrate. In this case, the electrolyte membrane may be formed by filling the pores of the porous substrate with particles obtained by bonding the non-fluorine-based electrolyte material to an inorganic substance. Such electrolyte membranes can be used as partitions placed between the positive and negative electrodes of fuel cells and electrolytic devices. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide an electrolyte material and an electrolyte membrane that are excellent in ionic conductivity without reducing mechanical strength.

Brief Description of the Drawings

[0021] [Figure 1] A diagram showing a production example of an electrolyte membrane which is one embodiment of the present invention. [Figure 2] A diagram showing the chemical structure of the electrolyte material used in Experiment 1.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the electrolyte material and the electrolyte membrane according to the present invention will be described.

[0023] [Electrolyte Material] The electrolyte material according to the present invention is a non-fluorine-based electrolyte material composed of a carbon chain skeleton having 1 to 11 carbon atoms and containing a functional group having an electron-withdrawing property and an ion-exchange group. As can be understood from the name "non-fluorine-based electrolyte material", the electrolyte material according to the present invention is composed of a compound that does not contain fluorine.

[0024] Examples of the electrolyte material include hydrocarbon compounds having structures represented by the following general formulas (a1), (a2), and (a3).

Chemical formula

[0025] In the general formulas (a1) to (a3), a plurality of R1 are each independently a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or a functional group having an electron-withdrawing property. Examples of the functional group having an electron-withdrawing property include a chloro group, a bromo group, an iodo group, a nitro group, a cyano group, a sulfonic acid group (-SO3H), a phosphoric acid group (-H2PO4), a phosphonic acid group (-H2PO3), and a carboxylic acid group (-COOH). The plurality of R1 may be the same as each other or different from each other. In general formulas (a1) to (a3), R2 is a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an electron-withdrawing functional group. Examples of electron-withdrawing functional groups include chloro group, bromine group, iodo group, nitro group, cyano group, sulfonic acid group (-SO3H), phosphate group (-H2PO4), phosphonic acid group (-H2PO3), and carboxylic acid group (-COOH).

[0026] Furthermore, in general formulas (a1) to (a3), R3 is an ion exchange group. Examples of ion exchange groups in the case of proton-conducting electrolyte membranes include sulfonic acid groups, phosphate groups, phosphonic acid groups, and carboxylic acid groups, but other acidic functional groups can also be used. On the other hand, examples of ion exchange groups in the case of anion-conducting electrolyte membranes include quaternary ammonium groups and imidazolium groups.

[0027] Sulfonic acid groups, phosphate groups, phosphonic acid groups, and carboxylic acid groups are both ion exchange groups and electron-withdrawing functional groups. Therefore, if R3 is both an ion exchange group and an electron-withdrawing functional group, such as a sulfonic acid group, then the multiple R1 and R2 groups do not necessarily have to be electron-withdrawing functional groups.

[0028] [Electrolyte membrane] An electrolyte membrane can be formed by preparing a solution containing the electrolyte material and polymer raw materials described above, and then forming a film using this solution. In this case, a reactive functional group may be introduced into the electrolyte material, and this reactive functional group may be used to bond to the polymer as a side chain. Alternatively, if at least one of the multiple R1 and R2 groups is a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, or a carboxylic acid group, these acidic functional groups may be used to bond to the polymer without introducing additional reactive functional groups. In the configuration of the electrolyte membrane, the composition ratio of the electrolyte material and polymer described above can be appropriately adjusted according to the application of the electrolyte membrane. The film thickness of the electrolyte membrane can also be appropriately adjusted according to the application. From the viewpoint of mechanical strength of the electrolyte membrane, a larger film thickness is preferable, but from the viewpoint of reducing overpotential due to membrane resistance, a thinner film thickness is preferable.

[0029] Furthermore, an electrolyte membrane can be formed by preparing a solution containing the aforementioned electrolyte material and an appropriately selected reaction accelerator, impregnating a reinforcing material such as a nonwoven fabric or a porous substrate with this solution, and then drying it. Alternatively, an electrolyte membrane can be formed by preparing a polymer solution containing the aforementioned electrolyte material, impregnating a reinforcing material such as a nonwoven fabric or a porous substrate with this solution, and then drying it. An electrolyte membrane with such a structure is called a pore-filling membrane. By using a reinforcing material such as a nonwoven fabric or a porous substrate, the mechanical strength of the electrolyte membrane can be increased, allowing for a thinner film thickness. This makes it possible to reduce overvoltage based on membrane resistance. In view of the spirit of the present invention, the reinforcing material used in such an electrolyte membrane is preferably a resin made of a non-fluorinated organic compound, and is preferably formed from polyolefins such as polyethylene, polypropylene, polybutylene, polymethylpentene, copolymers of polypropylene and polyethylene, and heat-resistant crosslinked polyethylene, as well as polycarbonate, polyimide, polyester, polyethersulfone, polyetherketone, polyetheretherketone, polysulfone, polysulfide, polyamide, polyamideimide, polyphenylene, polyether, polyetherimide, and polyetheramide.

[0030] Furthermore, as shown in the example in Figure 1, an electrolyte membrane 1 can be formed by molding inorganic particles 10 containing the above-mentioned electrolyte material into the pores 21 of a porous substrate 20 having pores with an inner diameter of 10 to 1000 nm. In an electrolyte membrane with such a configuration, proton conduction by the so-called Packed-acid mechanism occurs, and behavior specific to the temperature and / or humidity dependence of ionic conductivity may be observed. In view of the spirit of the present invention, the porous substrate 20 used in the electrolyte membrane 1 is preferably a resin made of a non-fluorinated organic compound, and is preferably formed from polyolefins such as polyethylene, polypropylene, polybutylene, polymethylpentene, copolymers of polypropylene and polyethylene, and heat-resistant crosslinked polyethylene, as well as polycarbonate, polyimide, polyester, polyethersulfone, polyetherketone, polyetheretherketone, polysulfone, polysulfide, polyamide, polyamideimide, polyphenylene, polyether, polyetherimide, and polyetheramide.

[0031] The method for forming the inorganic particles 10 into the pores 21 of the porous substrate 20 is not particularly limited, but may be carried out as follows. In the following explanation, zirconium phosphonate-based inorganic particles will be used as an example, but the composition of the inorganic particles 10 is not limited thereto.

[0032] As a starting material, zirconium alkoxide, a chelating agent, and a catalyst are reacted in a solvent to produce a precursor in which the chelating agent is coordinated to zirconium. The precursor is dissolved in a suitable solvent, and the solution is applied to a porous substrate 20 to impregnate the precursor into the pores 21. Next, a diphosphonic acid compound corresponding to one form of the electrolyte material disclosed in the present invention is dissolved in a suitable solvent, and the solution is applied to the porous substrate 20 impregnated with the precursor, thereby converting the precursor into zirconium phosphonate-based inorganic particles. In this way, an electrolyte membrane 1 can be formed in which inorganic particles 10 are filled into the pores 21 of the porous substrate 20.

[0033] [Experiment 1] Next, in order to investigate the action and effects of the electrolyte material according to the present invention, the ionic conductivity of a sample consisting of six types of nonfluorine-based compounds represented by formulas (1) to (6) shown in Figure 2 was measured.

[0034] Of formulas (1) to (6), formulas (1) to (3) and (6) correspond to the general formula (a1) described above, formula (4) corresponds to general formula (a2), and formula (5) corresponds to general formula (a3). Formula (1) corresponds to the case in general formula (a1) where all R1 are chloro groups and both R2 and R3 are phosphonic acid groups. Formulas (2) to (5) correspond to the case in general formulas (a1) to (a3) ​​where all R1 are hydrogen atoms and both R2 and R3 are phosphonic acid groups. Formula (6) corresponds to the case in general formula (a1) where all R1 are hydrogen atoms, R2 is a methyl group, and R3 is a phosphonic acid group. In formula (6), one phosphonic acid group functions as both an ion exchange group and an electron-withdrawing functional group. In the following explanation, samples represented by formulas (1) to (6) will be referred to as samples (1) to (6), respectively.

[0035] Samples (1) to (6) were all purchased from Tokyo Chemical Industry Co., Ltd. All samples (1) to (6) are in powder form.

[0036] Ionic conductivity was measured using an AMETEK potentiostat (PARSTAT MC 1000) and the AC impedance measurement method. The measurement procedure is described below.

[0037] First, a cylindrical flat plate made of polyetheretherketone resin was prepared, with a diameter of 20 mm and a height of 10 mm, and having a through-hole with an inner diameter of 4 mm in the center. The flat plate was then fixed to the lower electrode of the potentiostat so that its flat upper surface was in close contact with the lower surface of the plate, and 10 mg of the six types of samples were loaded into the through-hole of the plate. Next, a bottomed cylindrical upper electrode with an outer diameter of 3 mm was inserted into the through-hole containing the sample and pressed down, compressing the sample inside the through-hole until its thickness reached 388 μm. The pressure applied by the upper electrode varied depending on the sample, but was approximately 860 atmospheres (about 87 MPa).

[0038] Next, an AC voltage of 100 mV was applied to the sample sandwiched between the upper and lower electrodes in a frequency band from 0.1 Hz to 1.0 MHz, and the current flowing through the sample was measured using the two-terminal method. From the current value obtained from the measurement, the electrical resistance R [Ω] was determined, and the ionic conductivity σ [S / cm] was calculated from this electrical resistance R using the following equation (1).

number

[0039] The measured ionic conductivity values ​​for each sample are shown in Table 1 below. Table 1 lists the samples and their measured values ​​in descending order of ionic conductivity.

[0040] [Table 1]

[0041] As can be seen from Table 1, samples (1) and (2), which consist of a carbon chain skeleton with 1 carbon atom, had significantly higher ionic conductivity compared to the other samples. In particular, sample (1), in which R1 is a chloro group (Cl) with electron-withdrawing properties, showed extremely high ionic conductivity. From this, it was inferred that the smaller the number of carbon atoms in the carbon chain skeleton, and that if R1, R2, and R3 bonded to the carbon chain skeleton are all either electron-withdrawing functional groups or ion-exchange groups, the ionic conductivity will improve.

[0042] On the other hand, samples (5) and (4), which contain benzene rings in their carbon chain skeleton, exhibited lower ionic conductivity compared to samples (1) and (2), but showed ionic conductivity 3 to 10 times greater than samples (3) and (6), which have a similar number of carbon atoms but are straight-chain hydrocarbons.

[0043] [Experiment 2] Based on the results of Experiment 1, the ionic conductivity of diphosphonic acid (with 2 ion exchange groups) or phosphonic acid (with 1 ion exchange group) samples with 1 to 8 carbon atoms in the carbon chain skeleton was measured to investigate the relationship between the number of carbon atoms in the carbon chain skeleton, the number of ion exchange groups, and ionic conductivity. The apparatus and measurement procedure used for measuring ionic conductivity were the same as in Experiment 1.

[0044] The structures and ionic conductivity of the samples used in Experiment 2 are shown in Table 2 below. The leftmost column in Table 2 shows the structure of the carbon chain skeleton of the sample, and the two rightmost columns show the ionic conductivity of diphosphonic acid and phosphonic acid having the carbon chain skeleton shown in the leftmost column. In Table 2, columns marked with "-" indicate that the ionic conductivity of the sample was not measured. Also, in Table 2, columns marked (1), (2), (3), (4), (5), and (6) indicate the measurement results of samples (1), (2), (3), (4), (5), and (6) from Experiment 1. For example, the diphosphonic acid with a carbon skeleton of "CCl2" shows the ionic conductivity of sample (1) measured in Experiment 1. Note that, except for sample (6), the phosphonic acid samples have a phosphonic acid group bonded to one end of the carbon chain skeleton and a hydrogen atom bonded to the other end.

[0045] [Table 2]

[0046] As can be seen from Table 2, diphosphonic acid and phosphonic acid samples, whose carbon chain skeleton is an alkylene group, showed a tendency for ionic conductivity to decrease as the number of carbon atoms increased. Considering that alkylene groups are electron-donating, the reason for this result is thought to be a negative effect: as the number of carbon atoms in the alkylene group increases, the negative charge of the ion exchange group becomes unstable, reducing the degree of acid dissociation and thus decreasing ionic conductivity.

[0047] Furthermore, when comparing diphosphonic acid and phosphonic acid with the same carbon chain skeleton, diphosphonic acid (compounds with two ion exchange groups) tended to have higher ionic conductivity than phosphonic acid (compounds with one ion exchange group). This tendency was observed only when the number of carbon atoms in the carbon chain skeleton was less than 6. The ratio of ionic conductivity between diphosphonic acid and phosphonic acid with the same carbon chain skeleton was not uniform, but varied between approximately 1 and 7 times depending on the number of carbon atoms. Regarding the relationship between the ionic conductivity and ion concentration of electrolytes, the Nernsto-Einstein equation holds true when the ion concentration is low, and conductivity and ion concentration are proportional. When the ion concentration is high, the interactions between ions become significant, and the increase in conductivity gradually slows down, eventually remaining almost constant or even decreasing. In short, it is expected that simply doubling the number of ion exchange groups will only double the ionic conductivity at most. In Experiment 2, the fact that diphosphonic acid, which has the same carbon chain skeleton, sometimes exhibited ionic conductivity more than twice that of phosphonic acid cannot be explained solely by the difference in the number of ion exchange groups between diphosphonic acid and phosphonic acid, suggesting a qualitative change in the ion exchange groups. As a possible cause of such a qualitative change, a mechanism was considered in which the two phosphonic acid groups of diphosphonic acid improve each other's acid dissociation degree through electron-withdrawing properties. Furthermore, since the ionic conductivity of diphosphonic acid and phosphonic acid only became equal when the number of carbon atoms increased to six, it was considered that the range affected by electron-withdrawing groups is limited to up to five carbon atoms, with the carbon atom to which the electron-withdrawing group is bonded being the first carbon atom, in the case of alkylene groups.

[0048] On the other hand, the ionic conductivity of diphosphonic acid samples (4) and (5), which contain a benzene ring in their carbon chain skeleton, was close to that of diphosphonic acid in a linear hydrocarbon with two fewer carbon atoms. Two reasons were considered for why the decrease in ionic conductivity with increasing carbon number was more gradual in carbon skeletons containing a benzene ring compared to alkylene groups. Specifically, in samples (4) and (5), the number of carbon atoms in the shortest path connecting the two phosphonic acids along the molecular structure was 4 and 6, respectively, which is 2 less than the total number of carbon atoms in samples (4) and (5). From this, it was considered that the number of carbon atoms in the shortest path between ion exchange groups and electron-withdrawing groups is what affects ionic conductivity. Furthermore, because the benzene ring exhibits a mesomeric effect due to its electron resonance structure, the ortho and para positions of the carbon to which the electron-withdrawing group is attached tend to exhibit electron-withdrawing properties. Thus, the property that the effect of electron-withdrawing groups propagates easily over long distances in benzene rings was also considered to be a reason why the decrease in ionic conductivity with respect to carbon number is gradual.

[0049] As described above, in electrolyte materials made of non-fluorinated organic compounds, a guideline obtained from the present invention is to keep the carbon chain skeleton between the ion exchange group and the electron-withdrawing group below a certain length in order to achieve high ionic conductivity by utilizing electron-withdrawing functional groups other than fluorine. This differs from the prior art, which required linking groups with 6 or more carbon atoms to be used when bonding ion exchange groups to the polymer main chain. Furthermore, the present invention also provides a technology for an electrolyte membrane in which an electrolyte material having a structure in which multiple acid functional groups are bonded to a short carbon chain skeleton is used, and at least one of these acid functional groups is used to bond the electrolyte material to inorganic particles, and the inorganic particles are filled into the pores of a porous substrate. [Explanation of Symbols]

[0050] 1...Electrolyte membrane 10...Inorganic particles 20...Porous base material 21…Pore

Claims

1. A non-fluorinated electrolyte material comprising a carbon chain skeleton having 1 to 11 carbon atoms, containing an electron-withdrawing functional group and an ion-exchange group.

2. The non-fluorinated electrolyte material according to claim 1, wherein the ion exchange group is one of a sulfonic acid group, a phosphate group, a phosphonic acid group, and a carboxylic acid group.

3. The non-fluorinated electrolyte material according to claim 1, wherein the electron-withdrawing functional group is a chloro group, a bromo group, an iodine group, a nitro group, a cyano group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, or a carboxylic acid group.

4. The non-fluorinated electrolyte material according to claim 1, wherein the carbon chain skeleton comprises a saturated carbon chain skeleton having 1 to 8 carbon atoms or an aromatic hydrocarbon.

5. The non-fluorinated electrolyte material according to claim 1, wherein the carbon chain skeleton is a saturated carbon chain skeleton having 1 to 4 carbon atoms.

6. An electrolyte membrane formed from a non-fluorinated electrolyte material according to any one of claims 1 to 5.

7. Porous substrate and The porous substrate is provided with the non-fluorine-based electrolyte material according to any one of claims 1 to 5, An electrolyte membrane having the following properties.

8. Porous substrate and The pores of the porous substrate are filled with particles obtained by bonding the non-fluorine-based electrolyte material according to any one of claims 1 to 5 to an inorganic substance. An electrolyte membrane having the following properties.

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