Electrochemical device

Abstract

To provide an electrode structure of an electrochemical cell, an electrochemical cell, and an electrochemical device capable of reducing the thickness of the electrochemical cell in the lamination direction and facilitating the assembly of the electrochemical device.SOLUTION: An electrode structure includes a sheet-like electrode base material 20 made of a porous material. The electrode base material 20 includes an electrode function part 21 and a seal function part 22. The electrode function part 21 has a diffusion layer and a catalyst layer. The seal function part 22 is arranged at least in the outer peripheral region of the electrode function part 21, and is formed by impregnating an elastomer into the electrode base material 20.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an electrode structure of an electrochemical cell, an electrochemical cell, and an electrochemical device.

Background Art

[0002] As an electrochemical device such as an electrolyzer or a fuel cell, there is known one that uses a stack in which a plurality of electrochemical cells are stacked, and electrolysis or power generation of a substance is performed by each electrochemical cell in the stack (for example, see Patent Document 1).

[0003] The electrochemical device described in Patent Document 1 is an electrolyzer for carbon dioxide, and an electrochemical cell having the following structure is used. The electrochemical cell includes an anode electrode and a cathode electrode, an electrolyte membrane disposed between these electrodes, and a separator disposed on the surfaces of each electrode on the side opposite to the side where the electrolyte membrane is present. Both electrodes and the electrolyte membrane are integrated, and in that state, the periphery is held by a holding frame. An anode solution flow path is formed between one separator and the anode electrode, and a CO2 gas flow path is formed between the other separator and the cathode electrode. The anode electrode and the cathode electrode are connected to a power source. An anode solution containing water is flowed through the anode solution flow path, and carbon dioxide gas is flowed through the CO2 gas flow path.

[0004] In this electrochemical cell, when a voltage of a power source is applied to the anode electrode and the cathode electrode, at the anode electrode, water in the anode solution is oxidized to generate oxygen gas and hydrogen ions. The hydrogen ions generated at this time permeate the electrolyte membrane and proceed to the cathode electrode side. At the cathode electrode, carbon monoxide is generated by the reduction reaction of carbon dioxide in the CO2 gas flow path, and reacts with the hydrogen ions that have permeated the electrolyte membrane to generate water. The carbon monoxide generated at the cathode electrode is taken out through an external discharge passage. In this type of electrochemical cell, an elastomeric seal is provided between the holding frame that holds the periphery of the electrode and the electrolyte membrane and the adjacent separator to seal the space between them. This prevents the leakage of solution and gas from the solution flow path and the gas flow path.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the above-described electrochemical cell, an elastomeric seal is provided to prevent fluid from leaking to the outside from the periphery of the flow path. The elastomeric seal is formed to bulge toward the mating contact member side to restrict the leakage of fluid. When the mating contact member is pressed, it is crushed and exhibits a sealing function in that state. In the above-described electrochemical cell, since the seal is formed to bulge in the stacking direction of the cell, the thickness of the electrochemical cell in the stacking direction tends to increase.

[0007] Further, in the above-described electrochemical cell, since the elastomeric seal is formed to bulge in the stacking direction of the cell, the total amount of crushing of each seal increases when a plurality of stacked electrochemical cells are fastened and fixed in the stacking direction. Therefore, it is difficult to firmly fasten a plurality of electrochemical cells when assembling the electrochemical device.

[0008] Therefore, the present invention aims to provide an electrode structure, an electrochemical cell, and an electrochemical device for an electrochemical cell that can reduce the thickness of the electrochemical cell in the stacking direction and facilitate the assembly of the electrochemical device. And the present invention contributes to the mitigation or reduction of the impact of climate change.

Means for Solving the Problems

[0009] In order to solve the above problems, the electrode structure, electrochemical cell, and electrochemical device according to the present invention adopt the following configurations. That is, the electrode structure of the electrochemical cell according to one aspect of the present invention includes a sheet-like electrode base material made of a porous material (for example, the electrode base material 20 in the embodiment), and the electrode base material is provided with an electrode functional part having a diffusion layer and a catalyst layer (for example, the electrode functional part 21 in the embodiment), and a seal functional part (for example, the seal functional part 22 in the embodiment) disposed at least in the outer peripheral region of the electrode functional part and impregnated with an elastomer in the electrode base material.

[0010] The electrochemical cell of this aspect is provided with an electrode functional part and a seal functional part surrounding at least the outer peripheral region of the electrode functional part on an electrode base material made of a porous material. And the seal functional part is configured by impregnating an elastomer into the porous material of the electrode base material. For this reason, the elastomer of the seal functional part is supported by the porous material of the electrode base material. Therefore, since the seal functional part is not easily crushed even when pressed against other members in the stacking direction, it is not necessary to previously bulge the seal part greatly in the stacking direction. Therefore, when the electrochemical cell of this aspect is adopted, the electrochemical cell can be thinned in the stacking direction, and when assembling the electrochemical device, a plurality of electrochemical cells can be easily fastened and fixed.

[0011] The seal functional part may be overlapped on the electrode base material to form a flow path for the electrochemical reaction fluid between the seal functional part and the electrode functional part (for example, the first separator 13 and the second separator 14 in the embodiment), or may be configured to be able to contact a holding frame of the separator (for example, the holding frame 30 in the embodiment).

[0012] In this case, since the seal functional part of the electrode structure contacts the adjacent separator or its holding frame, the seal functional part of the electrode structure can prevent the electrochemical reaction fluid from leaking out from the flow path between the separator and the electrode functional part.

[0013] At least a part of the outer edge of the electrode base material may be provided with an energization part (for example, the energization part 40 in the embodiment) that is electrically conductive to the electrode functional part and is not impregnated with the elastomer.

[0014] In this case, without adding a complicated energization structure, the electrode functional part of the electrode structure can be connected to an external electric circuit such as a power supply circuit through the energization part on the outer edge of the electrode structure.

[0015] An electrochemical cell according to an aspect of the present invention includes a pair of sheet-like electrode structures (for example, the electrode structures 11A and 11B in the embodiment), an electrolyte membrane (for example, the electrolyte membrane 12 in the embodiment) disposed between the pair of electrode structures and allowing permeation of ions, and a pair of separators (for example, the first separator 13 and the second separator 14 in the embodiment) disposed so as to overlap with the surfaces of each of the electrode structures on the side opposite to the side where the electrolyte membrane exists and forming a flow path for an electrochemical reaction fluid (for example, the anode-side flow path 15 and the cathode-side flow path 16 in the embodiment) between the electrode structures. The pair of electrode structures includes a sheet-like electrode base material (for example, the electrode base material 20 in the embodiment) made of a porous material, and the electrode base material is provided with an electrode functional part (for example, the electrode functional part 21 in the embodiment) having a diffusion layer and a catalyst layer, and a seal functional part (for example, the seal functional part 22 in the embodiment) disposed at least in the outer peripheral region of the electrode functional part and formed by impregnating the electrode base material with an elastomer. The seal functional part of each of the electrode structures is in contact with the separator or a holding frame of the separator (for example, the holding frame 30 in the embodiment).

[0016] An electrochemical device according to an aspect of the present invention includes a plurality of the electrochemical cells, a pair of end face plates (for example, the end face plate 2 in the embodiment) sandwiching the plurality of electrochemical cells from both sides in the stacking direction, and a fastening member (for example, the fastening member 3 in the embodiment) that fastens the pair of end face plates in the proximity direction to fix the plurality of electrochemical cells to each other.

Advantages of the Invention

[0017] According to the present invention, it is possible to reduce the thickness of the electrochemical cell in the stacking direction and facilitate the assembly of the electrochemical device. By adopting the present invention, it is possible to contribute to the mitigation or reduction of the impact of climate change.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the embodiments described below, the same reference numerals are given to the common parts, and some of the overlapping descriptions will be omitted.

[0020] FIG. 1 is a perspective view of the electrochemical device of the present embodiment. The electrochemical device of the present embodiment is an electrolysis device 1 that electrolyzes carbon dioxide into carbon compounds such as carbon monoxide. The electrolysis device 1 includes a plurality of electrochemical cells 10 (110, 210) laminated in the thickness direction, a pair of end plates 2 that sandwich the plurality of electrochemical cells 10 (110, 210) from both sides in the lamination direction, and a fastening member 3 (for example, a bolt and a nut) that fastens the pair of end plates 2 in the proximity direction to fix the plurality of electrochemical cells 10 (110, 210) to each other.

[0021] <First Embodiment> FIG. 2 is an exploded perspective view of the electrochemical cell 10 of the present embodiment, and FIG. 3 is an exploded front view of a part of the electrochemical cell 10. FIG. 4 is a view showing a cross section corresponding to the IV-IV cross section of FIG. 2, and FIG. 5 is a view showing a cross section corresponding to the V-V cross section of FIG. 2. The electrochemical cell 10 includes a pair of sheet-like electrode structures 11A and 11B, an electrolyte membrane 12 disposed between the pair of electrode structures 11A and 11B, a first separator 13 facing one side of one electrode structure 11A in the lamination direction, and a second separator 14 facing the other side of the other electrode structure 11B in the lamination direction. In the present embodiment, the electrode structures 11A and 11B, the electrolyte membrane 12, the first separator 13, and the second separator 14 are all formed in a horizontally long rectangular shape when viewed from the front. However, these shapes are not limited to this shape.

[0022] One of the electrode structures 11A constitutes an anode electrode, and the other electrode structure 11B constitutes a cathode electrode. One of the electrode structures 11A and the other electrode structure 11B are respectively connected to the positive electrode and the negative electrode of a power source (not shown). The detailed structure of the electrode structures 11A and 11B will be described in detail later.

[0023] The electrolyte membrane 12 is a membrane material such as a solid polymer membrane that allows ions to permeate between the anode electrode (one of the electrode structures 11A) and the cathode electrode (the other electrode structure 11B).

[0024] The first separator 13 is disposed so as to overlap with the surface of one electrode structure 11A on the side opposite to the side where the electrolyte membrane 12 is present. The first separator 13 forms a flow path 15 through which an electrochemical reaction fluid (for example, an anode solution containing water) flows between it and one electrode structure 11A. This flow path 15 formed between the first separator 13 and one electrode structure 11A is hereinafter referred to as the "anode-side flow path 15".

[0025] On one side in the width direction of the first separator 13, a fluid inlet 17i for introducing a fluid such as an anode solution into the anode-side flow path 15 is formed. On the other side in the width direction of the first separator 13, a fluid outlet 17o for discharging the fluid discharged from the anode-side flow path 15 to the outside together with products such as oxygen is formed. Both the fluid inlet 17i and the fluid outlet 17o penetrate the first separator 13 in the thickness direction.

[0026] At positions overlapping with the fluid inlet 17i and the fluid outlet 17o of other members laminated on the first separator 13, similar through-holes T1 and T3 are formed. For this reason, the fluid is introduced in parallel into each anode-side flow path 15 of the plurality of stacked electrochemical cells 10 through the through-hole T1 and the fluid inlet 17i. Further, the fluid and the products are discharged to the outside from each anode-side flow path 15 of the plurality of stacked electrochemical cells 10 through the fluid outlet 17o and the through-hole T3.

[0027] The second separator 14 is disposed so as to overlap with the surface of the other electrode structure 11B on the side opposite to the side where the electrolyte membrane 12 is present. The second separator 14 forms a flow path 16 through which an electrochemical reaction fluid (for example, carbon dioxide gas) flows between it and the other electrode structure 11B. This flow path 16 formed between the second separator 14 and the other electrode structure 11B is hereinafter referred to as the "cathode-side flow path 16".

[0028] On one side in the width direction of the second separator 14, a fluid inlet 18i for introducing a fluid such as carbon dioxide gas into the cathode-side flow path 16 is formed. On the other side in the width direction of the second separator 14, a fluid outlet 18o for discharging the fluid discharged from the cathode-side flow path 16 to the outside together with products such as carbon monoxide is formed. Both the fluid inlet 18i and the fluid outlet 18o penetrate the second separator 14 in the thickness direction.

[0029] At positions overlapping the fluid inlet 18i and the fluid outlet 18o of the other members laminated on the second separator 14, similar through-holes T2 and T4 are formed. For this reason, the fluid is introduced in parallel into each cathode-side flow path 16 of the plurality of laminated electrochemical cells 10 through the through-hole T2 and the fluid inlet 18i. Further, the fluid and the products are discharged to the outside from each cathode-side flow path 16 of the plurality of laminated electrochemical cells 10 through the fluid outlet 18o and the through-hole T4.

[0030] Next, the detailed structure of the electrode structures 11A and 11B will be described. Each of the electrode structures 11A and 11B includes a sheet-like electrode base material 20 made of a porous material such as carbon nonwoven fabric. The electrode base material 20 is formed in a rectangular shape having the same size as the electrolyte membrane 12. The electrode base material 20 is provided with an electrode functional part 21 having a diffusion layer and a catalyst layer (not shown), and a seal functional part 22 disposed in the outer peripheral region of the electrode functional part 21. The seal functional part 22 is formed by impregnating an elastomer such as rubber in the outer peripheral region of the electrode base material 20 made of a porous material. The elastomer of the seal functional part 22 is impregnated in the electrode base material 20 so as to cover the outer peripheral part of the electrode functional part 21 and the outer peripheral parts of the through-holes T1, R2, T3, and T4. Note that the electrode structures 11A and 11B and the electrolyte membrane 12 in the present embodiment are a membrane electrode assembly in which the electrode structures 11A and 11B are directly joined to the electrolyte membrane 12. However, the electrode structures 11A and 11B can also be used as a structure separate from the electrolyte membrane 12.

[0031] The seal function part 22 in which the outer peripheral region of the electrode base material 20 is impregnated with an elastomer is capable of contacting the adjacent first separator 13 and second separator 14 on the end face in the stacking direction. The seal function parts 22 of the respective electrode structures 11A and 11B are pressed against the outer peripheral regions of the first separator 13 and second separator 14 adjacent in the stacking direction when the electrolytic device 1 described later is assembled. As a result, the outer peripheral regions of the anode side flow path 15 and the cathode side flow path 16 are sealed by the seal function part 22, and the outer peripheral regions of the respective through-holes T1, T2, T3, and T4 are also sealed by the seal function part 22.

[0032] Next, the assembly of the electrolytic device 1 will be described. In advance, constituent members of a plurality of electrochemical cells 10 (a membrane electrode assembly composed of an electrolyte membrane 12 and electrode structures 11A and 11B, a first separator 13, and a second separator 14) are prepared. In this state, the electrochemical cell 10 in which the first separator 13, the membrane electrode assembly, and the second separator 14 are stacked in this order is superposed on the electrochemical cell 10 in which the constituent members are similarly stacked. In this state, a pair of end face plates 2 (see FIG. 1) are arranged at the ends in the stacking direction, and the pair of end face plates 2 are tightened by a fastening member 3 in a direction in which they approach each other. As a result, in each electrochemical cell 10 of the electrolytic device 1, the seal function parts 22 of the respective electrode structures 11A and 11B of the membrane electrode assembly are pressed against the adjacent separators. As a result, leakage of fluid from each flow path of each electrochemical cell 10 is prevented.

[0033] As described above, in the electrode structures 11A and 11B of the present embodiment, an electrode functional portion 21 and a seal functional portion 22 are provided on an electrode base material 20 made of a porous material. The seal functional portion 22 is disposed in a region surrounding the outer peripheral region of the electrode functional portion 21, and is configured by impregnating the porous material of the electrode base material 20 with an elastomer. In the electrode structures 11A and 11B of the present embodiment, since the elastomer of the seal functional portion 22 is supported by the porous material of the electrode base material 20, the seal functional portion 22 is not easily crushed even when pressed against other members in the stacking direction, and reliably adheres to the mating member. Therefore, it is not necessary to previously greatly bulge the seal functional portion 22 in the stacking direction for the electrode structures 11A and 11B. Therefore, when the electrode structures 11A and 11B, the electrochemical cell 10, and the electrolysis device 1 of the present embodiment are employed, the electrochemical cell 10 can be thinned in the stacking direction, and when assembling the electrolysis device 1 (electrochemical device), a plurality of electrochemical cells 10 can be easily fastened and fixed.

[0034] Further, in the electrode structures 11A and 11B of the present embodiment, the seal functional portion impregnated with the elastomer is adapted to contact the first separator 13 and the second separator 14. For this reason, in the electrochemical cell 10 employing the electrode structures 11A and 11B of the present embodiment, the seal functional portion 22 of the electrode structures 11A and 11B can surely prevent fluid from leaking to the outside from the anode-side flow path 15 and the cathode-side flow path 16 between the electrode functional portion 21 and the respective separators 13 and 14.

[0035] Furthermore, in the electrode structures 11A and 11B of the present embodiment, the elastomer is also impregnated in the peripheral regions of the through-holes T, T2, T3, and T4 of the electrode structures 11A and 11B. For this reason, leakage of fluid from the peripheral regions of the through-holes T, T2, T3, and T4 can also be surely prevented. Therefore, when this configuration is adopted, so-called cross leakage in which fluid flowing in one flow path mixes with fluid flowing in another flow path can also be surely prevented.

[0036] In addition, the electrode structures 11A and 11B of the present embodiment are formed to have substantially the same size as the outer edge portions of the first separator 13 and the second separator 14. Therefore, when assembling the electrolyzer 1, by aligning the outer edge portions of the electrode structures 11A and 11B with the outer edge portions of the adjacent separators 13 and 14, the electrode structures 11A and 11B can be easily positioned at the proper positions. Therefore, when adopting this configuration, the assembly work of the electrolyzer 1 becomes easier.

[0037] <Second Embodiment> FIG. 6 is a partially exploded front view of the electrochemical cell 110 of the present embodiment, and FIG. 7 is a cross-sectional view corresponding to FIG. 4 of the first embodiment of the electrochemical cell 110 of the present embodiment. Further, FIG. 8 is a cross-sectional view corresponding to FIG. 5 of the first embodiment of the electrochemical cell 110 of the present embodiment. The basic configuration of the electrochemical cell 110 of the present embodiment is substantially the same as that of the first embodiment, but the size of the electrolyte membrane 112 is formed to be slightly smaller than that of the electrode structures 11A and 11B. And the electrolyte membrane 112 is held by a rectangular holding frame 30 whose outer edge has the same size as the electrode structures 11A and 11B. The holding frame 30 is formed of, for example, a non-conductive material. The outer peripheral edge portions of each of the electrode structures 11A and 11B abut against the end faces in the stacking direction of the holding frame 30 in the seal function portion 22. Therefore, the seal function portion 22 of one of the electrode structures 11A is in close contact with the first separator 13 and one surface of the holding frame 30, and the seal function portion 22 of the other electrode structure 11B is in close contact with the second separator 14 and the other surface of the holding frame 30.

[0038] Although the seal function portions 22 at the outer peripheral edge portions of the electrode structures 11A and 11B of the electrochemical cell 110 of the present embodiment are in close contact with the holding frame 30 outside the electrolyte membrane 112, the same effects as those of the first embodiment described above can be obtained. Even when the electrochemical cell 110 of the present embodiment is adopted, the electrochemical cell 110 can be thinned in the stacking direction, and when assembling the electrolyzer 1 (electrochemical device), a plurality of electrochemical cells 110 can be easily fastened and fixed.

[0039] <Third Embodiment> FIG. 9 is an exploded front view of a part of the electrochemical cell of the present embodiment. The electrochemical cell 210 of the present embodiment has substantially the same basic configuration as that of the first embodiment. However, each of the electrode structures 211A and 211B is provided with a current-carrying portion 40 that is electrically connected to the power source 45 at a part of the outer peripheral edge of the electrode base material 20. The current-carrying portion 40 is electrically conductive to the electrode functional portion 21 in the central region and is not impregnated with an elastomer with respect to the porous material of the electrode base material 20.

[0040] Since the electrochemical cell 210 of the present embodiment has the same basic configuration as that of the first embodiment, the same effects as those of the first embodiment described above can be obtained. In addition, the electrochemical cell 210 of the present embodiment is provided with a current-carrying portion 40 that is electrically conductive to the electrode functional portion 21 and is not impregnated with an elastomer at a part of the outer edge of the electrode base material 20. Therefore, the electrode functional portion 21 can be easily connected to the power source 45 through the current-carrying portions 40 of the electrode structures 211A and 211B without adding a complicated current-carrying structure.

[0041] Note that the present invention is not limited to the above embodiments, and various design changes are possible without departing from the gist thereof. For example, in the above embodiments, fluid inlets 17i, 18i, fluid outlets 17o, 18o, through holes T1, T2, T3, T4, etc. are provided on both sides in the width direction of each electrochemical cell 10 to form a fluid introduction path and a discharge path. However, the fluid introduction path and the discharge path are not limited to this. Any other form may be used as long as fluid can be appropriately introduced into the anode-side flow path 15 and the cathode-side flow path 16 and the reacted fluid can be appropriately discharged from each flow path.

[0042] Further, in the above-described embodiment, the elastomer is impregnated only in the outer peripheral region of the electrode functional portion 21 of the electrode base material 20, but the impregnation region of the elastomer (sealing functional portion 22) may be at least in the outer peripheral portion of the electrode functional portion 21. For example, a part of the impregnation region of the elastomer (sealing functional portion 22) may enter in the direction of the electrode functional portion 21.

[0043] In the above-described embodiment, the electrolyzer 1 for carbon dioxide electrolysis, which is a form of the electrochemical device, has been described, but the electrochemical device is not limited thereto. The electrochemical device may be an electrolyzer that electrolyzes a substance other than carbon dioxide. Furthermore, the electrochemical device may be a fuel cell that generates power by supplying a fuel gas and an oxidant gas to an electrode structure, respectively.

Explanation of Reference Numerals

[0044] 1... Electrolyzer 2... End face plate 3... Fastening member 10, 110, 210... Electrochemical cell 11A, 11B, 211A, 211B... Electrode structure 12, 112... Electrolyte membrane 13... First separator (separator) 14... Second separator (separator) 15... Anode side flow path (flow path of electrochemical reaction fluid) 16... Cathode side flow path (flow path of electrochemical reaction fluid) 20... Electrode base material 21... Electrode functional portion 22... Sealing functional portion 30... Holding frame 40... Current conducting portion

Claims

【Claim 1】 A plurality of electrochemical cells, a pair of end plates that sandwich the plurality of electrochemical cells from both sides in the stacking direction, and a fastening member that fastens the pair of end plates in the approaching direction to fix the plurality of electrochemical cells to each other, wherein the electrochemical cell comprises a pair of sheet-like electrode structures, an electrolyte membrane disposed between the pair of electrode structures and allowing permeation of ions, and a pair of separators disposed to overlap the surfaces of each electrode structure on the side opposite to the side where the electrolyte membrane is present, and forming a flow path for an electrochemical reaction fluid between the separators and the electrode structures, wherein the pair of electrode structures comprises a sheet-like electrode base material made of a porous material, and on the electrode base material, there are provided an electrode functional part having a diffusion layer and a catalyst layer, and a sealing functional part disposed at least in the outer peripheral region of the electrode functional part and formed by impregnating the electrode base material with an elastomer, wherein the sealing functional part of each electrode structure is in contact with the separator or a holding frame of the separator, the separator is provided with a fluid inlet and a fluid outlet penetrating in the thickness direction, and at positions overlapping the fluid inlet or the fluid outlet in another member laminated on the separator, through holes similar to the fluid inlet or the fluid outlet are formed, and an outer peripheral region of the through hole is impregnated with the elastomer. An electrochemical device is characterized by this.

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