Electrochemical Devices

Abstract

To provide an electrochemical element that enables predetermined gas to be efficiently separated and captured, in an energy-saved manner and with a small-scale facility.SOLUTION: An electrochemical element according to an embodiment of the present invention comprises: an external wall; and a bulkhead which is arranged inside the external wall, and defines a plurality of cells extending from a first end face to a second end face. Each of the plurality of cells has a first cell and a second cell. A functional electrode including a first active material is formed on a surface of the bulkhead defining the first cells and a counter electrode including second active material is arranged inside the second cells.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrochemical device. [Background technology]

[0002] The development of technologies for separating and recovering a specific gas from a gas mixture is being continuously advanced. In particular, in recent years, it has become necessary to suppress carbon dioxide (CO2) emissions in order to mitigate global warming, and efforts have been made to separate and recover carbon dioxide from gas mixtures. A representative example of such efforts is the Carbon Dioxide Capture, Utilization and Storage (CCUS) cycle. Here, for example, chemical adsorption, physical adsorption, cryogenic separation, membrane separation, and electrochemical recovery methods are known for recovering carbon dioxide. However, at present, all of these technologies have insufficient carbon dioxide recovery capacity, require a very large amount of energy for recovery, and require large-scale facilities for recovery, and various issues remain to be considered for practical application. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2018-533470 Summary of the Invention [Problem to be solved by the invention]

[0004] A primary object of the present invention is to provide an electrochemical element capable of efficiently separating and recovering a specified gas using energy-saving and small-scale equipment. [Means for solving the problem]

[0005] An electrochemical element according to an embodiment of the present invention includes an outer peripheral wall and a partition wall disposed inside the outer peripheral wall and defining a plurality of cells extending from a first end face to a second end face. The plurality of cells includes a first cell and a second cell, a functional electrode including a first active material is formed on a surface of the partition wall defining the first cell, and a counter electrode including a second active material is disposed inside the second cell. In one embodiment, the first cells and the second cells are arranged in an alternating manner. In one embodiment, the first cell includes a gas flow path, and the functional electrode is formed on the partition wall so as to surround the gas flow path. In one embodiment, the second cell is filled with the counter electrode. In one embodiment, the counter electrode comprises a conductive substrate and the second active material dispersed in the substrate. In one embodiment, the substrate comprises a carbonaceous material. In one embodiment, the counter electrode further comprises an ionic liquid. In one embodiment, the partition wall is impregnated with an ionic liquid, and the ionic liquid is the same as the ionic liquid contained in the counter electrode. In one embodiment, the first active material comprises anthraquinone and the second active material comprises polyvinylferrocene. Effect of the Invention

[0006] According to an embodiment of the present invention, an electrochemical element capable of efficiently separating and recovering a predetermined gas with energy saving and small-scale equipment can be realized. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic perspective view of an electrochemical device according to one embodiment of the present invention. [Diagram 2] 2 is a schematic cross-sectional view of the electrochemical device of FIG. 1 in a direction parallel to the extending direction of the cell. [Diagram 3]3 is an enlarged schematic cross-sectional view of a main part of the electrochemical element of FIG. 1 and FIG. 2 in a direction perpendicular to the extending direction of the cells. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments.

[0009] A. Overall configuration of the electrochemical element An electrochemical device according to an embodiment of the present invention separates and recovers a predetermined gas (eg, carbon dioxide) from a gas mixture using an electrochemical process.

[0010] Fig. 1 is a schematic perspective view of an electrochemical element according to one embodiment of the present invention; Fig. 2 is a schematic cross-sectional view parallel to the direction in which the cells of the electrochemical element of Fig. 1 extend; and Fig. 3 is an enlarged schematic cross-sectional view of a main part of the electrochemical element of Fig. 1 and Fig. 2 in a direction perpendicular to the direction in which the cells extend. The electrochemical element 100 of the illustrated example has an outer peripheral wall 10 and partition walls 40 disposed inside the outer peripheral wall 10 and defining a plurality of cells 30, 30, ... extending from a first end face 20a to a second end face 20b.

[0011] In the embodiment of the present invention, the plurality of cells 30, 30, ... have a first cell 30a and a second cell 30b. A functional electrode 50 containing a first active material is formed on the surface of the partition wall 40 that defines the first cell 30a. With this configuration, it is possible to greatly increase the contact area between the functional electrode and a gas mixture at a predetermined flow rate (substantially, the gas to be separated and collected) while ensuring sufficient strength. As a result, it is possible to separate and collect a predetermined gas (e.g., carbon dioxide) with extremely high efficiency. Furthermore, it is possible to efficiently separate and collect a predetermined gas (e.g., carbon dioxide) with a small-scale facility, and the energy required for separating and collecting the gas can be significantly reduced. Thus, according to the embodiment of the present invention, by adopting the so-called honeycomb structure as described above as the basic structure of the electrochemical element, it is possible to efficiently separate and collect gas with energy saving and small-scale facility. A gas flow path 70 is formed in the center (i.e., the portion where the functional electrode 50 is not formed) of the first cell 30a in the cross section perpendicular to the cell extension direction. The functional electrode 50 may be formed on the entire surface of the partition wall 40 (i.e., so as to surround the gas flow channel 70) as in the illustrated example, or may be formed on a part of the surface of the partition wall. In consideration of the efficiency of gas separation and recovery, it is preferable that the functional electrode 50 is formed on the entire surface of the partition wall 40. A counter electrode 60 containing a second active material is disposed inside the second cell 30b. The second cell 30b is typically filled with the counter electrode 60.

[0012] The arrangement pattern of the first cells 30a and the second cells 30b may be appropriately set according to the purpose as long as the effect of the embodiment of the present invention can be obtained. In the illustrated example, the first cells 30a and the second cells 30b are arranged alternately (i.e., in a checkerboard pattern). With such a configuration, the counter electrode can function well, and therefore the electrochemical reaction in the functional electrode can be performed well. Although not illustrated, for example, the ratio of the second cells 30b in the multiple cells 30, 30, . . . may be reduced as long as the number (ratio) in which the counter electrode can function is secured. That is, the ratio of the first cells 30a (effectively, the functional electrode 50 and the gas flow channel 70) may be increased. For example, the second cells 30b may be arranged so as not to be adjacent to each other. Here, "not adjacent to each other" means that the two cells do not share any side or vertex of the partition wall that defines each cell. With this configuration, the contact area between the gas mixture at a given flow rate (substantially the gas to be separated and collected) and the functional electrode can be further increased, and as a result, the gas separation and collection performance can be further improved. In this case, the first cell 30a can typically share the partition wall 40 with at least one second cell 30b.

[0013] The shape of the electrochemical element can be appropriately designed depending on the purpose. The electrochemical element 100 in the illustrated example is cylindrical (the cross-sectional shape in the direction perpendicular to the cell extension direction is circular), but the electrochemical element may be a columnar shape with an elliptical or polygonal (e.g., rectangular, pentagonal, hexagonal, octagonal) cross-sectional shape. The length of the electrochemical element can be appropriately set depending on the purpose. The length of the electrochemical element can be, for example, 5 mm to 500 mm. The diameter of the electrochemical element can be appropriately set depending on the purpose. The diameter of the electrochemical element can be, for example, 20 mm to 500 mm. In addition, when the cross-sectional shape of the electrochemical element is not circular, the diameter of the maximum inscribed circle inscribed in the cross-sectional shape (e.g., polygonal) of the electrochemical element can be set as the diameter of the electrochemical element. The aspect ratio (diameter:length) of the electrochemical element is, for example, 1:12 or less, for example, 1:5 or less, or for example, 1:1 or less. If the aspect ratio is within this range, the current collection resistance can be set within an appropriate range.

[0014] The operation of the electrochemical element will be outlined below. For example, the case will be described in which the gas to be separated and collected is carbon dioxide, the first active material of the functional electrode 50 contains anthraquinone, and the second active material of the counter electrode 60 contains polyvinylferrocene. The anthraquinone of the functional electrode can be reduced in the charging mode (the functional electrode is the negative electrode).

[0015] When a gas mixture containing carbon dioxide is passed through the gas flow path 70 of the electrochemical element, the following reaction (1) occurs between the anthraquinone in a reduced state on the functional electrode 50 and carbon dioxide, and the carbon dioxide is captured by the anthraquinone. In this way, carbon dioxide can be recovered. [ka]

[0016] At this time, the polyvinylferrocene of the counter electrode 60 can be oxidized, i.e., the polyvinylferrocene can function as an electron source for the reduction of anthraquinone in the charging mode.

[0017] Also, the anthraquinone in the functional electrode 50 can be oxidized in the discharge mode (functional electrode is positive).

[0018] When the anthraquinone that has captured carbon dioxide is oxidized in the functional electrode 50, the following reaction (2) occurs, and the carbon dioxide captured by the anthraquinone is released from the bond with the anthraquinone. In this way, the carbon dioxide can be released from the functional electrode 50 to the gas flow path 70. [ka]

[0019] At this time, the polyvinylferrocene of the counter electrode 60 can be reduced, i.e., the polyvinylferrocene can function as an electron acceptor during the oxidation of anthraquinone in the discharge mode.

[0020] As described above, by switching the polarity of the functional electrode (and necessarily the counter electrode), the electrochemical element (effectively, the functional electrode) can capture (capture, adsorb) and release carbon dioxide. In particular, by utilizing anthraquinone in a reduced state in the charging mode, carbon dioxide can be separated and captured (captured) from a gas mixture. For example, exhaust gas from factories and thermal power plants contains about 10% carbon dioxide, and by passing a gas mixture having the same composition as such exhaust gas through an electrochemical element according to an embodiment of the present invention, the carbon dioxide concentration can be reduced to 0.1% or less.

[0021] The components of the electrochemical device will be specifically described below.

[0022] B. Periphery walls and bulkheads The outer peripheral wall 10 and the partition wall 40 are typically made of a porous body containing insulating ceramics. The insulating ceramic typically contains silicon carbide and silicon (hereinafter, sometimes referred to as silicon carbide-silicon composite). The ceramic contains silicon carbide and silicon in a total amount of, for example, 90% by mass or more, for example, 95% by mass or more. With such a configuration, the volume resistivity of the outer peripheral wall and the partition wall at 400°C can be sufficiently increased, and leakage current caused by electronic conductivity can be suppressed. Therefore, only the desired electrochemical reaction can be favorably performed over the entire functional electrode 50 and the counter electrode 60. The ceramic may contain a substance other than the silicon carbide-silicon composite. An example of such a substance is strontium.

[0023] The silicon carbide-silicon composite typically contains silicon carbide particles as aggregates and silicon as a binder for binding the silicon carbide particles. In the silicon carbide-silicon composite, for example, a plurality of silicon carbide particles are bound by silicon so as to form pores (voids) between the silicon carbide particles. That is, the partition wall 30 and the outer peripheral wall 40 containing the silicon carbide-silicon composite may be, for example, a porous body.

[0024] In one embodiment, the voids of the partition 30 and the outer peripheral wall 40 are impregnated with an ionic liquid. With this configuration, the partition and the outer peripheral wall (particularly the partition) can function well as a separator between the functional electrode and the counter electrode. Furthermore, by being impregnated with the ionic liquid, electronic conductivity can be suppressed, and only the desired electrochemical reaction can be efficiently performed. As the ionic liquid, any appropriate ionic liquid can be used depending on the purpose, the configuration of the electrochemical element, and the like. The ionic liquid can typically contain an anion component and a cation component. Examples of the anion component of the ionic liquid include halides, sulfuric acid, sulfonic acid, carbonate, bicarbonate, phosphoric acid, nitric acid, hydrochloric acid, acetic acid, PF6, and the like. - , BF4 -, triflates, nonaflates, bis(triflyl)amides, trifluoroacetic acids, heptafluorobutanoic acids, haloaluminates, triazolides, and amino acid derivatives (e.g., proline where the proton on the nitrogen has been removed). Cationic components of ionic liquids include, for example, imidazolium, pyridinium, pyrrolidinium, phosphonium, ammonium, sulfonium, thiazolium, pyrazolium, piperidinium, triazolium, pyrazolium, oxazolium, guanadinium, and dialkylmorpholinium. Ionic liquids include, for example, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim] + [BF4] - When the gas species to be separated and recovered is carbon dioxide, water may be electrolyzed due to the potential window, so it is preferable to use a non-aqueous ionic liquid.

[0025] The silicon content in the silicon carbide-silicon composite material is preferably 10% by mass to 40% by mass, more preferably 15% by mass to 35% by mass. If the silicon content is too low, the strength of the outer peripheral wall and the partition walls may be insufficient. If the silicon content is too high, the outer peripheral wall and the partition walls may not be able to maintain their shape during firing.

[0026] The average particle diameter of the silicon carbide particles is preferably 3 μm to 50 μm, more preferably 3 μm to 40 μm, and further preferably 10 μm to 35 μm. When the average particle diameter of the silicon carbide particles is in this range, the volume resistivity of the outer peripheral wall and the partition walls can be set to the appropriate range as described above. If the average particle diameter of the silicon carbide particles is too large, the raw material may clog the die when forming the outer peripheral wall and the partition walls. The average particle diameter of the silicon carbide particles can be measured, for example, by a laser diffraction method.

[0027] The average pore diameter of the outer peripheral wall 10 and the partition walls 40 is preferably 2 μm to 20 μm, and more preferably 10 μm to 20 μm. When the average pore diameter of the outer peripheral wall and the partition walls is within this range, the ionic liquid can be impregnated well. If the average pore diameter is too large, the carbonaceous material in the counter electrode or the functional electrode may flow into the partition walls, which may result in an internal short circuit. The average pore diameter can be measured, for example, by a mercury porosimeter.

[0028] The porosity of the outer peripheral wall 10 and the partition walls 40 is preferably 15% to 60%, and more preferably 30% to 45%. If the porosity is too small, the outer peripheral wall and the partition walls may be significantly deformed during firing. If the porosity is too large, the strength of the outer peripheral wall and the partition walls may be insufficient. The porosity can be measured, for example, by a mercury porosimeter.

[0029] The thickness of the partition wall 40 can be appropriately set depending on the purpose. The thickness of the partition wall 40 can be, for example, 50 μm to 1.0 mm, or, for example, 70 μm to 600 μm. When the thickness of the partition wall is within this range, the mechanical strength of the electrochemical element can be made sufficient, and the opening area (the total area of ​​the cells in the cross section) can be made sufficient, and the gas separation and recovery efficiency can be significantly improved.

[0030] The density of the partition walls 40 can be appropriately set depending on the purpose. The density of the partition walls 40 is, for example, 0.5 g / cm 3 ~5.0g / cm 3 If the density of the partition wall is in this range, the electrochemical device can be made lighter and have sufficient mechanical strength. The density can be measured by, for example, the Archimedes method.

[0031] In one embodiment, the thickness of the outer peripheral wall 10 is greater than the thickness of the partition walls 40. With such a configuration, it is possible to suppress the outer peripheral wall from being broken, broken, cracked, or the like due to an external force. The thickness of the outer peripheral wall 10 is, for example, 0.1 mm to 5 mm, and can be, for example, 0.3 mm to 2 mm.

[0032] The cells 30, 30, ... have any appropriate cross-sectional shape in a direction perpendicular to the cell extension direction. In the illustrated example, the partition walls 40 that define the cells are perpendicular to each other, and define cells having a quadrangular (square in the illustrated example) cross-sectional shape except for the part in contact with the outer peripheral wall 10. The cross-sectional shape of the cells may be a square, a circle, an ellipse, a triangle, a pentagon, a hexagon or more polygon, etc. In one embodiment, the cross-sectional shape of the cells is a quadrangle of the same shape (for example, a square, a rectangle, a parallelogram, a rhombus). With such a configuration, it is easy to form the functional electrode and the counter electrode, and there is an advantage that the pressure loss when the gas flows is small and the separation and recovery performance is excellent.

[0033] The cell density in the direction perpendicular to the cell extension direction (i.e., the number of cells 30, 30, ... per unit area) can be appropriately set depending on the purpose. The cell density is, for example, 4 cells / cm 2 ~320 cells / cm 2 If the cell density is within this range, the contact area between the gas mixture at a given flow rate (essentially, the gas to be separated and recovered) and the functional electrode can be made extremely large. As a result, a given gas (e.g., carbon dioxide) can be separated and recovered with extremely high efficiency. For example, if the mounting density of a flat gas separation element in which a functional electrode and a counter electrode are opposed to each other via a separator is 0.2 m 2 / L, whereas the above configuration is 2m 2 / L (approximately 10 times) can be secured. As a result, it becomes possible to efficiently separate and capture a specific gas (e.g., carbon dioxide) using small-scale equipment, and the energy required to separate and capture the gas can be significantly reduced. Furthermore, by securing such a high level of mounting density, it may become possible to separate and capture carbon dioxide from the atmosphere (Direct Air Capture: DAC).

[0034] C. Functional electrode As described above, the functional electrode includes a first active material and is configured to collect and release a predetermined gas (e.g., carbon dioxide). A representative example of the first active material is anthraquinone. Anthraquinone can collect (capture, adsorb) and release carbon dioxide by the electrochemical reaction described in the above section A. Anthraquinone may be polyanthraquinone (i.e., a polymer). Examples of polyanthraquinone include poly(1,4-anthraquinone), poly(1,5-anthraquinone), poly(1,8-anthraquinone), and poly(2,6-anthraquinone) represented by the following formula (I). These may be used alone or in combination. [ka]

[0035] The first active material may be any suitable material other than anthraquinone, so long as it can capture and release (particularly capture) a predetermined gas (e.g., carbon dioxide). Examples of such materials include tetrachlorohydroquinone (TCHQ), hydroquinone (HQ), dimethoxybenzoquinone (DMBQ), naphthoquinone (NQ), tetracyanoquinodimethane (TCNQ), dihydroxybenzoquinone (DHBQ), and polymers thereof.

[0036] The functional electrode may further include a substrate. Here, the term "substrate" refers to a component that shapes an electrode (layer) and maintains its shape. Furthermore, the substrate may support a first active material. The substrate is typically conductive. Examples of the substrate include carbonaceous materials. Examples of the carbonaceous materials include carbon nanotubes (e.g., single-walled carbon nanotubes, multi-walled carbon nanotubes), carbon black, KetjenBlack, carbon black Super P, and graphene. By using such a carbonaceous material as the substrate, electron transfer can be easily performed, so that the oxidation-reduction reaction of the first active material can be performed well. For example, when anthraquinone or polyanthraquinone is used as the first active material, the average pore diameter of the substrate is preferably 2 nm to 50 nm, more preferably 2 nm to 20 nm, and even more preferably 3 nm to 10 nm. If the average pore diameter is too small, the first active material may not be supported inside. If the average pore diameter is too large, the first active material may fall off during operation of the functional electrode. The average pore diameter of the substrate may vary depending on the first active material. For example, when naphthoquinone is used as the first active material, the average pore diameter is preferably about 2 / 3 of the above size. The average pore diameter can be calculated, for example, by using BJH analysis in the nitrogen gas adsorption method.

[0037] The content of the first active material in the functional electrode may be, for example, 10% by mass to 70% by mass, or, for example, 20% by mass to 50% by mass, based on the total mass of the functional electrode. When the content of the first active material is within such a range, good gas recovery and release performance can be achieved.

[0038] The thickness of the functional electrode may be, for example, 20 μm to 300 μm, or may be, for example, 100 μm to 200 μm. If the thickness of the functional electrode is in this range, a desired gas flow path can be secured while maintaining good gas recovery and release performance.

[0039] The functional electrode can be formed, for example, by applying a functional electrode-forming material containing a first active material, a substrate, and a binding binder to the partition wall surface under reduced pressure and then subjecting the functional electrode-forming material to a heat treatment.

[0040] D. Counter electrode As described above, the counter electrode can function as an electron source for the reduction of the first active material, and can also function as an electron receiver for the oxidation of the first active material. That is, the counter electrode plays an auxiliary role for the functional electrode to function well. As described above, the counter electrode includes a second active material. As the second active material, any appropriate material can be used as long as it can perform electron exchange well with the functional electrode. Examples of the second active material include polyvinylferrocene, poly(3-(4-fluorophenyl)thiophene), and the like.

[0041] The counter electrode may further comprise a substrate, as described above in section C for the functional electrode. In one embodiment, the counter electrode comprises a second active material dispersed in the substrate. The second active material dispersed in the substrate provides Excellent electronic conductivity can be achieved within the electrode.

[0042] The counter electrode may further contain an ionic liquid. When the counter electrode contains an ionic liquid, the counter electrode can function three-dimensionally, and the capacity of donating and receiving electrons can be increased. The ionic liquid is as described above in section B regarding the outer wall and the partition wall. In one embodiment, the ionic liquid contained in the counter electrode is the same as the ionic liquid contained in the outer wall and the partition wall (particularly, the partition wall). With this configuration, the electrochemical element can be manufactured simply and easily, and adverse effects on the electrochemical reaction of the functional electrode can be prevented.

[0043] The counter electrode is disposed inside the cell 30b as described above, and typically fills the cell 30b. By filling the cell 30b with the counter electrode, the electrolyte (ionic liquid) can be continuously supplied to the functional electrode for a long period of time.

[0044] The content of the second active material in the counter electrode may be, for example, 10% by mass to 90% by mass, or, for example, 30% by mass to 70% by mass, based on the total mass of the counter electrode. If the content of the second active material is within this range, the amount of electrolyte (ionic liquid) used can be reduced, and the second active material in the counter electrode can be effectively utilized.

[0045] When the counter electrode contains an ionic liquid, the content thereof may be, for example, 10% by mass to 90% by mass, or, for example, 30% by mass to 70% by mass, based on the total mass of the counter electrode. If the content of the ionic liquid is within such a range, the electrolyte (ionic liquid) can be continuously supplied to the functional electrode for a long period of time.

[0046] The counter electrode can be formed, for example, by placing in a cell (typically, by filling the cell) a counter electrode-forming material including a second active material, a substrate, preferably an ionic liquid, and optionally a solvent or dispersion medium. [Industrial Applicability]

[0047] Electrochemical devices according to embodiments of the present invention may be suitably used for separating and recovering a specific gas from a gas mixture, and may be suitably used in a carbon dioxide capture, utilisation and storage (CCUS) cycle in particular. [Explanation of symbols]

[0048] 10 Peripheral wall 20a 1st end face 20b 2nd end face 30 cells 30a First cell 30b Second cell 40 Bulkhead 50 Functional Electrodes 60 Counter Electrode 70 Gas flow path 100 Electrochemical element

Claims

1. An outer perimeter wall; a partition wall disposed inside the outer peripheral wall and defining a plurality of cells extending from the first end surface to the second end surface; having the plurality of cells includes a first cell and a second cell; a functional electrode including a first active material is formed on a surface of the partition wall that defines the first cell; a counter electrode including a second active material is disposed within the second cell; the second cell is filled with the counter electrode; Electrochemical element.

2. The electrochemical device according to claim 1 , wherein the first cells and the second cells are arranged in an alternating manner.

3. The electrochemical device according to claim 1 or 2, wherein the first cell includes a gas flow path.

4. 4. The electrochemical element according to claim 3, wherein the functional electrode is formed on the partition wall so as to surround the gas flow channel.

5. 5. The electrochemical element according to claim 1, wherein the counter electrode comprises a conductive matrix and the second active material dispersed in the matrix.

6. The electrochemical device of claim 5 , wherein the substrate comprises a carbonaceous material.

7. The electrochemical device according to claim 5 or 6, wherein the counter electrode further comprises an ionic liquid.

8. 8. The electrochemical element according to claim 7, wherein the partition wall is impregnated with an ionic liquid, and the ionic liquid is the same as the ionic liquid contained in the counter electrode.

9. 9. The electrochemical device according to claim 1, wherein the first active material comprises anthraquinone and the second active material comprises polyvinylferrocene.

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