JP5854522B2 - Adhesive composition - Google Patents

Description

  The present invention relates to an adhesive composition.

  An electrochemical reaction device such as a solid oxide fuel cell or a solid oxide water vapor electrolysis device is configured with a cell composed of a solid electrolyte and two electrodes respectively provided on both sides thereof as a basic unit. One of these two electrodes is called an anode electrode, and the other is called a cathode electrode. For example, in a solid oxide fuel cell including a cell configured as described above, a fuel gas such as hydrogen gas is supplied to the anode electrode from the outside, and an oxidizing gas such as air is supplied to the cathode electrode from the outside. The solid oxide fuel cell is configured to generate electric energy by the electrochemical reaction of the supplied gas.

  The generation of this electric energy is usually performed at an operating temperature of 800 ° C. to 1200 ° C., but in recent years, improvements have been made to solid electrolytes that exhibit good ionic conductivity even at low temperatures, whereby 300 ° C. to 700 ° C. Solid oxide fuel cells have been developed that can generate electrical energy even at operating temperatures.

  Actually, the solid oxide fuel cell is configured to obtain a desired current by stacking a plurality of the cells via a separator. When the cell is a flat plate type, a fuel gas passage is provided between one surface of the solid electrolyte on which the anode electrode is formed and a separator provided opposite the one surface (between the cell and the separator). The fuel gas is bonded so that the fuel gas does not leak outside. Similarly, between the other surface of the solid electrolyte on which the cathode electrode is formed and the separator provided opposite to the other surface (between the cell and the separator), an oxidation gas passage is secured and oxidation is performed. Bonded so that gas does not leak outside.

  Further, in the case of a solid oxide fuel cell, when the cell is cylindrical, a plurality of cells are connected in the axial direction (cells), or both ends of the connected cells are closed with caps (cell and current collecting electrode). In addition, the cells are connected in series (stacked) by connecting the cells in the radial direction (cells).

  The adhesion between such cells, between the cell and the separator, and between the cell and the current collecting electrode requires both electrical conductivity due to electrical connection and airtightness depending on the adhesion location. Conventionally, such adhesion that requires both conductivity and airtightness at the same time is achieved by directly connecting cells, between the cell and the separator, and by directly connecting the cell and the current collecting electrode, A glass as an adhesive composition melted by applying heat was applied, cooled and cured to form a sealing material as an adhesive, thereby ensuring airtightness (for example, Patent Document 1). In particular, Patent Document 1 discloses that by dispersing ceramic fibers in glass, even if the glass contained in the sealing material is softened at the operating temperature of the solid oxide fuel cell, the softened glass is made of ceramic fibers. By remaining, the effect that the sealing material can be prevented from flowing out from a predetermined position is exhibited. Also known as adhesive compositions are those made of silver paste or platinum paste in which silver or platinum is dispersed in a solvent, or those containing a lanthanum chromite oxide.

JP 2006-185775 A

  However, even in the above-described Patent Document 1, when the end of a cylindrical cell is closed with a cap, there is a problem that a gap is generated between the cell and the cap, making it difficult to obtain an electrical connection. there were.

  Also, when silver paste or platinum paste is used as the adhesive composition, the solvent evaporates by firing, so the volume of the sealing material formed by firing is significantly reduced compared to the adhesive composition before firing. In addition, a gap is generated on the circumference of the cell, and it is more difficult to obtain an electrical connection. Therefore, the adhesive composition has to be repeatedly applied to fill the gap, which increases the work man-hours. Furthermore, the adhesive composition containing a lanthanum chromite oxide has a low conductivity of the lanthanum chromite oxide, so that it is difficult to efficiently generate electrical energy when used in a solid oxide fuel cell. There was a problem of being.

  An object of this invention is to provide the adhesive composition which can adhere | attach the adhesive part which needs electroconductivity reliably in view of an above-described problem.

In order to achieve the above object, the invention according to claim 1 is an adhesive composition comprising a metal powder and a glass powder dispersed in a liquid, and having airtightness and conductivity by firing after drying. The metal powder has a melting point higher than the operating temperature of the solid oxide fuel cell or the solid oxide steam electrolyzer, and further does not oxidize at the heating temperature when firing the metal powder; and Oxidizing at the heating temperature at the time of firing the metal powder comprises an expanding material powder whose volume expands to compensate for the volume reduced by the evaporation of the liquid, and the expanding material powder includes titanium, zirconium, is either europium, and aluminum, the glass powder, the metal powder are those having a softening point lower than the heating temperature at the time of firing, the adhesive composition after firing before Liquid is not included, and the volume after firing of the adhesive composition is larger than the volume after drying, the ratio of the volume after baking relative to the volume after drying, characterized in that it is 1.14 at the maximum.

  The invention according to claim 2 is characterized in that the conductive material powder is one of platinum, gold and silver, or an alloy mainly composed of these.

The invention according to claim 3 is characterized in that the metal powder and the glass powder are dispersed and formed into a sheet shape.

According to the adhesive composition of the first aspect of the present invention, the adhesive portion that requires electrical conductivity is securely adhered, and the solid portion does not melt even at the operating temperature of the solid oxide fuel cell. Since the state can be maintained, the airtightness of the bonded portion can be maintained without being affected by the pressure of the supplied fuel gas or the like. Moreover, since it is stable without being oxidized even at the operating temperature, the conductivity can be reliably maintained. Furthermore, since the oxide produced by oxidizing the expanding material powder is stable without being reduced even if it is exposed to a reducing gas, the airtightness can be reliably maintained. Moreover, since the volume expand | swells because the expansion | swelling material powder contained in an adhesive composition oxidizes, the reduction | decrease of the volume by the evaporation of a liquid can be supplemented. Therefore, the adhesive formed by firing the adhesive composition has a volume after expansion that is larger than that of the adhesive composition before firing by making up for the volume that the expansion material powder has expanded and reduced by evaporation of the liquid. Since the volume of the adhesive is prevented from decreasing, the airtightness of the bonded portion can be maintained without being affected by the pressure of the supplied fuel gas or the like. In addition, since the volume of the adhesive composition expands when the expansion material powder is oxidized, the gap of the adhesive portion can be filled. Furthermore, since the glass powder can be softened by heating for baking to densify the adhesive, the adhesive composition can be reliably sealed.

  Moreover, according to the adhesive composition of Claim 2, since it is stable without being oxidized at an operating temperature, electroconductivity can be reliably hold | maintained.

  Moreover, according to the adhesive composition of Claim 3, the efficient solid oxide fuel cell which can seal an adhesion part by a slurry coat method can be obtained.

It is a perspective view which shows the structure of the cylindrical cell of the solid oxide fuel cell which concerns on 1st Embodiment. It is a cross-sectional perspective view which shows the structure of a cell same as the above. It is sectional drawing which shows the usage example as a sealing material of an adhesive composition same as the above, (a) The state before joining, (b) It is a figure which shows the state after joining. It is sectional drawing which shows the usage example as an interconnector of an adhesive material composition same as the above. It is a perspective view which shows the structure of the cylindrical cell of the solid oxide steam electrolysis apparatus which concerns on 2nd Embodiment.

(1) Embodiment (1) -1 First Embodiment A preferred embodiment of the present invention will be described below with reference to the drawings. A cell 1 shown in FIG. 1 has a cylindrical shape, has a desired length, and is closed by a bottomed cylindrical cap 2 to constitute a solid oxide fuel cell.

  As shown in FIG. 2, the cell 1 includes a cathode electrode 3, an interconnector 4, a solid electrolyte 5, and an anode electrode 6. The cell 1 is formed by forming an interconnector 4, a solid electrolyte 5 and an anode electrode 6 as adhesives on the outside of a cathode electrode 3 formed by extrusion molding. In the cell 1, the anode electrode 6 and the solid electrolyte 5 are cut out in a slit shape on one surface to expose the cathode electrode 3, and the interconnector 4 is provided in the exposed portion. Although not shown, the cell 1 has a current collecting electrode bonded thereto, and is connected to an external circuit via the current collecting electrode.

  In the solid oxide fuel cell including the cell 1 configured as described above, a fuel gas such as hydrogen gas is supplied to the anode electrode 6 from the outside, and an oxidizing gas such as air is supplied to the cathode electrode 3 from the outside. In the cathode electrode 3, oxygen atoms receive electrons and generate oxygen ions. When the generated oxygen ions pass through the solid electrolyte 5 and reach the anode electrode 6, the oxygen ions are combined with hydrogen molecules to release electrons, and water is generated and discharged. At that time, the emitted electrons are supplied to the cathode electrode 3 via an external circuit (not shown). In this way, power is generated in the solid oxide fuel cell, and electric power can be taken out in an external circuit.

Each part which comprises the cell 1 is not specifically limited, It can form with the material similar to the past. For example, the anode electrode 6 is based on NiO (nickel oxide) -YSZ (yttria stabilized zirconia) cermet, the solid electrolyte 5 is based on YSZ (yttria stabilized zirconia), and the cathode electrode 3 is based on lanthanum manganate (LaMnO ₃ ). It can be formed of a perovskite oxide or the like.

  As shown in FIG. 3, the cell 1 is characterized by the configuration of the adhesive composition used for the bonded portion and the bonding method thereof. That is, the adhesive composition is thinly applied to the seal portion 10 as an adhesive portion formed between the outer peripheral surface of the end portion of the cell 1 and the inner periphery of the cylindrical portion of the cap 2, and is fired. The sealing material 11 is formed as an adhesive material that is airtight and also has electrical conductivity.

  The adhesive composition is produced by dispersing, in a liquid, a metal powder composed of an expansion material powder that retains airtightness and a conductive material powder that retains electrical conductivity, and glass powder. The liquid in which the metal powder and the glass powder are dispersed may be a vehicle obtained by dissolving a resin in a solvent.

The expanding material powder is a material having a melting point higher than 300 ° C. to 700 ° C. which is an operating temperature of a solid oxide fuel cell or a solid oxide steam electrolyzer, and whose volume expands by oxidation, such as titanium, zirconium can be composed of any of Yoo Ropiumu and aluminum.

  The conductive material powder is a material which has a melting point higher than the operating temperature and does not oxidize at the operating temperature, and can be composed of, for example, platinum, gold, silver, or an alloy mainly composed of these.

  The glass powder is composed of a glass material having a melting point higher than 300 ° C. to 700 ° C., which is the operating temperature of the solid oxide fuel cell, and having a softening point lower than the heating temperature when firing the metal powder. Can do.

  Next, an adhesion method for sealing the seal portion 10 using the adhesive composition configured as described above will be described. First, the adhesive composition is applied to the seal portion 10 between the cell 1 and the cap 2. The applied sealing composition is left to dry, whereby the solvent evaporates. Next, the seal composition applied to the seal portion 10 between the cell 1 and the cap 2 is baked at a predetermined heating temperature. By firing, the glass powder softens during firing by having a softening point lower than the heating temperature. Thereby, the gap generated in the seal portion 10 can be filled, and the denseness of the seal material 11 can be improved, so that the seal can be surely performed.

  In addition, since the liquid contained in the adhesive composition evaporates, the volume of the adhesive composition decreases accordingly. Incidentally, in the conventional adhesive composition, when the volume of the adhesive composition is reduced, a gap is generated in the seal portion 10, and it is necessary to repeatedly apply the adhesive composition to the seal portion 10 in order to fill the gap. .

  However, in the adhesive composition of the present invention, the expansion material powder contained in the adhesive composition is oxidized to expand its volume, so that it is possible to compensate for the decrease in volume caused by the evaporation of the liquid. Therefore, the sealing material 11 formed by firing the adhesive composition is fired in comparison with the adhesive composition before firing by making up for the volume reduced by the evaporation of the liquid by expanding the volume of the expanding material powder. Since the volume of the subsequent sealing material 11 is prevented from decreasing, the airtightness of the seal portion 10 can be maintained without being affected by the pressure of the supplied fuel gas or the like. Thus, according to the adhesive composition of the present invention, if the adhesive composition is provided on the seal portion 10 and the adhesive composition is baked, the seal portion 10 can be reliably sealed. Since it is not necessary to repeatedly provide the adhesive composition on the seal portion 10 as described above, the number of work steps can be significantly reduced. Moreover, the sealing material 11 can hold | maintain the electroconductivity of the cell 1 and the cap 2 because an adhesive material composition contains a electrically conductive material powder.

  In the adhesive composition, since the expansion material powder and the conductive material powder have melting points higher than the operating temperature of the solid oxide fuel cell, the adhesive material does not melt even at the operating temperature of the solid oxide fuel cell. Can maintain a solid state. Therefore, the adhesive formed from the adhesive composition can maintain the airtightness of the bonded portion without being affected by the pressure of the supplied fuel gas or the like.

  As described above, according to the adhesive composition of the present invention, even the seal portion 10 having a large gap can be reliably sealed. In particular, in the case of the cylindrical cell 1, the gap between the end of the cell 1 and the cap 2 is large, and is easily affected by the volume change of the sealing material 11. However, according to the present invention, the volume of the adhesive composition expands when the expandable powder is oxidized, so that the gap of the seal portion 10 can be filled. Furthermore, since the glass powder can be softened by heating for baking and the sealing material 11 can be densified, the adhesive composition can be reliably sealed.

  In addition, the adhesive composition can seal the adhesive portion by a slurry coating method by dispersing the metal powder and the glass powder in a vehicle obtained by dissolving a resin in a solvent.

  Further, since the expansion material powder is stable without being reduced even when exposed to the reducing gas at the operating temperature, the airtightness can be more reliably maintained.

  In addition, since the conductive material powder is stable without being oxidized even at the operating temperature, the conductivity can be reliably maintained.

  The sealing material 11 can also be used for sealing a seal portion (not shown) between the single cells when the single cells (not shown) are connected to each other.

  Further, as shown in FIG. 4, the cells 1 can be connected in series by an interconnector 4. That is, a plurality of cells 1A (1) and 1B (1) are arranged in the radial direction, and the adhesive composition is applied between the cathode electrode 3 of one cell 1A and the anode electrode 6 of the other cell 1B. . The applied adhesive composition is baked. Since the adhesive composition contains an expanding material powder that oxidizes and expands in volume, the volume of the interconnector 4 formed by firing the adhesive composition does not decrease compared to the adhesive composition before firing. . Therefore, the cells 1 can be connected in series without changing the positional relationship between the cells 1 before and after firing. Moreover, since the interconnector 4 can hold | maintain electroconductivity reliably by containing a conductive material powder, it can be made into a reliable stack.

  Moreover, the adhesion part of the cell 1 and the electrode for current collection is equipped with the adhesive formed by baking an adhesive composition. Thereby, the cell 1 and the current collecting electrode can be reliably electrically connected.

(1) -2 Second Embodiment Next, a case where the adhesive composition is applied to a solid oxide steam electrolysis apparatus will be described. In addition, the same code | symbol is attached | subjected about the structure similar to the cell in the case of the above-mentioned solid oxide fuel cell, and description is abbreviate | omitted for simplicity. As shown in FIG. 5, the cell 21 constituting the solid oxide steam electrolyzer is composed of an anode electrode 22, a solid electrolyte 5 and a cathode electrode 23. Further, although not shown, the cell 21 has a power supply electrode bonded thereto and is connected to an external power supply via the power supply electrode.

  In the solid oxide steam electrolyzer configured as described above, by introducing high-temperature steam into the cathode electrode 23, the steam is decomposed into hydrogen molecules and oxygen ions at the cathode electrode 23. Hydrogen molecules decomposed at the cathode electrode 23 are collected as hydrogen gas. On the other hand, the decomposed oxygen ions pass through the solid electrolyte 5, release electrons at the anode electrode 22, and are collected as oxygen gas. When the cells 21 configured as described above are connected and both ends thereof are closed with the cap 2, the seal portion 24 between the cells 21 and the cap 2 is formed by the sealing material 11 formed by firing the adhesive composition. Can be sealed. Thereby, the same effect as described above can be obtained. Of course, the adhesive composition can also be used to connect the cells 21 together.

  Moreover, the adhesion part of the cell 1 and the electrode for power supplies is equipped with the adhesive material formed by baking the adhesive composition. Thereby, the cell 1 and the power supply electrode can be reliably electrically connected.

  The present invention is not limited to this embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, in the above-described embodiment, the case where the adhesive composition contains a metal powder composed of an expansion material powder and a conductive material powder is described, but the present invention is not limited thereto, and the metal powder includes lanthanum and Chrome may be used. As a result, the adhesive composition has a high electrical conductivity and does not melt even at the operating temperature of the solid oxide fuel cell or the solid oxide steam electrolyzer without using a precious metal with few resources. Therefore, it is possible to form a sealing material that can maintain the hermeticity of the seal portion without being affected by the pressure of the supplied fuel gas or the like.

  An alkaline earth metal may be added to the lanthanum chromite oxide. As an alkaline earth metal, any one or two or more of magnesium, calcium, strontium, and barium can be added. Thereby, the compatibility between the chemical stability and other constituent materials can be improved.

  In the above-described embodiment, the case where the cell is a cylindrical type has been described. However, the present invention is not limited to this and can be applied to a flat plate type cell (not shown). In this case, between one surface of the solid electrolyte on which the anode electrode is formed and the separator provided opposite to the one surface (between the cell and the separator), a fuel gas passage is secured, Bonding can be performed so that the fuel gas does not leak to the outside.

  In the above-described embodiment, the case where a cell formed to have a desired length has been described. However, the present invention is not limited to this, and a plurality of unit length unit cells are connected in the axial direction to form a cell. It is good. In this case, it is good also as connecting a single cell to an axial direction with the sealing material formed with the adhesive composition.

  Further, in the above-described embodiment, the adhesive composition is described in the case where the metal powder and the glass powder are prepared by dispersing in a vehicle in which a resin is dissolved in a solvent. However, the adhesive may be formed by directly sintering the metal powder at the bonding portion.

  The adhesive composition may be prepared by dispersing metal powder and glass powder in a liquid in which resin is not dissolved. Thereby, the adhesive composition can seal an adhesion part by a slurry coat method.

  Further, the adhesive composition may be formed into a sheet by dispersing the metal powder and the glass powder. Thereby, it can seal easily according to the shape of an adhesion part.

(2) Example As an example, the volume ratio between the adhesive composition and the sealing material formed by firing the adhesive composition was examined. The adhesive composition according to Sample 1 was prepared by adding glass powder to Ti as an expanding material powder and Ag as a conductive material powder, and dispersing it in a solvent containing a resin and a surfactant. Sample 1 produced in this manner was dried and then fired to obtain a sealing material. The results of examining the weight ratio, volume ratio, etc. of the sample before and after firing are shown in Table 1.

  As shown in Table 1, although the resin, the surfactant and the solvent evaporate by drying and firing, the volume ratio (after firing / after drying) was 1.14. It has been found that the volume of the sealing material becomes larger than the adhesive composition because the weight and volume increase.

  Further, the adhesive composition according to Sample 2 was prepared by adding glass powder to Al as the expansion material powder and Ag as the conductive material powder and dispersing in a solvent containing a resin and a surfactant. Sample 1 produced in this manner was dried and then fired to obtain a sealing material. Table 2 shows the results of examining the weight ratio, volume ratio, and the like of the sample before and after firing.

  As shown in Table 2, although the resin, surfactant and solvent evaporate by drying and firing, the volume ratio (after firing / after drying) was 1.10. It has been found that the volume of the sealing material becomes larger than that of the adhesive composition because the weight and volume increase.

  From the above results, since the volume of the expansion material powder expands due to oxidation by containing the expansion material powder, the adhesive composition can form a sealing material having a volume larger than that of the adhesive composition. I understood.

1 cell (solid oxide fuel cell)
2 Cap (solid oxide fuel cell)
11 Sealing material (adhesive)

Claims (3)

A metal powder and glass powder are dispersed in a liquid, and an adhesive composition having airtightness and conductivity by firing after drying ,
The metal powder is
A conductive material powder having a melting point higher than the operating temperature of the solid oxide fuel cell or solid oxide steam electrolyzer, and not oxidized at the heating temperature when firing the metal powder;
Oxidizing at the heating temperature at the time of firing the metal powder, to make up the volume reduced by the evaporation of the liquid, so as to make up the expanding material powder, the volume expands,
The expanding material powder is any of titanium, zirconium, europium and aluminum,
The glass powder has a softening point lower than the heating temperature when firing the metal powder,
The adhesive composition after firing does not contain the liquid, and the volume after firing of the adhesive composition is larger than the volume after drying, and the ratio of the volume after firing to the volume after drying is the maximum. 1. Adhesive composition characterized by being 14.14 .   The adhesive composition according to claim 1, wherein the conductive material powder is any one of platinum, gold, and silver, or an alloy mainly composed of these.   The adhesive composition according to claim 1 or 2, wherein the metal powder and the glass powder are dispersed and formed into a sheet shape.

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