JP2007117893A - Electrochemical cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniaturized electrochemical cell with enhanced heat efficiency. <P>SOLUTION: This electrochemical cell 1 having electrodes 3, 4 disposed on both faces of an electrolyte 2 is integrally provided with gas permeable heat reflection layers 6, 7 on the outside of the electrodes 3, 4. The heat reflection layers 6, 7 are provided with porous metal layers 20 with a surface emissivity of 0.1 or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat retention structure of an electrochemical cell.

  Conventionally, an electrochemical cell that can separate and selectively take out oxygen from an oxygen-containing mixed gas such as air is known, and in recent years, utilizing the oxygen separation action of such an electrochemical cell, Toxic gases such as NOx and hydrocarbons discharged from factories and automobiles are being purified, and in general electrical equipment, oxygen enrichers using electrochemical cells are installed in the equipment. Attempts have been made to create a simple oxygen-enriched atmosphere in the room by mounting (see Patent Document 1 and Patent Document 2).

Patent Document 1 includes an oxygen pump element and a heating means (electric heater) for heating the oxygen pump element to an operating temperature (approximately 400 to 800 ° C.) in a space surrounded by a heat-insulating material having air permeability. An oxygen pump is disclosed, and Patent Document 2 discloses an oxygen pump in which heat reflection means for radiating heat rays from the heating means is provided on the inner wall of the heat insulating material.
JP 2003-215094 A JP 2003-212515 A

  By the way, the disclosed technologies according to Patent Documents 1 and 2 are all intended to improve the thermal efficiency of the heating means to the oxygen pump by preventing the oxygen pump element and the heating means from coming into direct contact with the atmosphere by the heat insulating material. However, the heat dissipation from the surface of the oxygen pump element to the heat insulation space has deteriorated the thermal efficiency, which is a factor that slows down the start time of the oxygen pump, and the power consumption by the heating means is large accordingly. It was an obstacle to energy saving. In addition, as in Patent Documents 1 and 2, the heat retaining structure surrounded by the heat insulating material leads to an increase in the size of the oxygen pump.

  The present invention has been made in view of the above problems, and is an electrochemical cell in which a gas-permeable heat reflection layer is provided on a cell electrode to suppress heat radiation from the cell, thereby improving thermal efficiency and miniaturization. The purpose is to provide.

  That is, the present invention according to claim 1 is an electrochemical cell including a cell in which electrodes are arranged on both sides of an electrolyte, and a heat reflecting layer having gas permeability is integrally provided outside the electrode. It is said.

  The present invention according to claim 2 is the electrochemical cell according to claim 1, wherein the heat reflecting layer includes a porous metal layer made of a metal having a surface emissivity of 0.1 or less. It is characterized by that.

  According to a third aspect of the present invention, in the electrochemical cell according to the second aspect, the metal layer is made of Ag or Au.

  Moreover, the present invention according to claim 4 is the electrochemical cell according to claim 2 or 3, wherein the metal layer is a thin plate, a vapor deposition layer, a sputtering layer, a plating layer, or a powder baking layer. It is characterized by comprising at least one kind.

  The present invention according to claim 5 is the electrochemical cell according to any one of claims 1 to 4, wherein an electrically insulating layer is provided on one surface of the heat reflecting layer. It is said.

  Moreover, the present invention according to claim 6 is the electrochemical cell according to any one of claims 1 to 5, wherein the cell uses an oxygen permeation using a solid electrolyte having oxygen ion conductivity as the electrolyte. It is characterized by being a cell.

  The present invention according to claim 7 is the electrochemical cell according to any one of claims 1 to 5, wherein the cell uses a hydrogen ion conductive solid electrolyte as the electrolyte. It is characterized by being a cell.

According to invention of Claims 1-4, by providing a heat | fever reflection layer integrally in the outer side of an electrode, radiation | emission of the heat | fever from a cell is suppressed and thermal efficiency can be improved. As a result, the temperature of the cell can be increased efficiently, and rapid start-up becomes possible. Further, even during operation, the cell can be kept at the operating temperature at all times, thereby enabling the heat independent operation. In addition, since the heat reflecting layer is gas permeable, it does not adversely affect the ventilation performance of oxygen and / or air. In addition, since the heat reflecting layer is in close contact with the electrode, a space can be saved and the size can be reduced.
As the heat reflection layer, an Ag material or an Au material having excellent heat resistance (high temperature oxidation resistance) and emissivity is used at a temperature of about 400 to 800 ° C., and a thin plate, a vapor deposition layer, a sputter layer, a plating layer, It is preferable to be composed of at least one powder baking layer.

  According to the fifth aspect of the present invention, in the configuration in which the heat reflecting layer is used as a feeding electrode or a collecting electrode by providing an electrical insulating layer on one surface of the heat reflecting layer, the metal layer It is possible to prevent a short circuit to other members while maintaining good heat radiation without affecting the heat emissivity, thereby improving the reliability.

  Hereinafter, an embodiment of an electrochemical cell according to the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the electrochemical cell 1 according to the present embodiment includes a cell 5 in which an electrode (cathode) 3 and an electrode 4 (anode) are arranged on both surfaces of a solid electrolyte 2, and an electrode 3 and an electrode 4, respectively. The heat reflection layers 6 and 7, the gas diffusion layers 8 and 9 disposed outside the heat reflection layers 6 and 7, and the separators 10 and 11 outside the heat diffusion layers 6 and 7 are configured.

When the cell 5 is used as an oxygen permeable cell, for example, a structure in which electrodes 3 and 4 made of LSC: La _0.6 Sr _0.4 CoO ₃ are arranged on both surfaces of a solid electrolyte 2 made of yttria-added zirconia (YSZ), or cobalt A solid electrolyte 2 made of added lanthanum gallate (LSGMC) is used in which electrodes made of SSC: Sm _0.5 Sr _0.5 CoO ₃ are arranged on both surfaces.
In the oxygen permeable cell, as shown in FIG. 7, by applying a DC voltage (V) between the electrodes 3 and 4, external air selectively permeates only oxygen from the cathode side to the anode side of the cell 5. Thereby, the oxygen concentration in the space on the anode side can be increased.

When the cell 5 is used as a hydrogen permeable cell, for example, a solid electrolyte 2 made of SrCeO ₃ and electrodes 3 and 4 made of Pt—ZrO ₂ are arranged on both surfaces, or a solid electrolyte 2 made of BaZrCeGaO _3. Are used in which electrodes 3 and 4 made of Pt are arranged on both sides.
In the hydrogen permeable cell, as shown in FIG. 8, by applying a DC voltage (V) between the electrodes 3 and 4, external air (including water vapor) is directed from the anode side to the cathode side of the cell 5. Only hydrogen can be selectively permeated, whereby the oxygen concentration in the cathode-side space can be increased.

  The gas diffusion layers 8 and 9 are made of a foam metal and contribute to the diffusion and distribution of gas (external air and oxygen). In particular, when the cell 5 is an oxygen permeable cell, foamed Ag, foamed SUS, foamed inconel, or the like is used. When the cell 5 is a hydrogen permeable cell, foamed Ni is present in the gas diffusion layer 8 on the cathode side, Foamed Ag is used for the gas diffusion layer 9. The separators 10 and 11 are made of SUS or the like, and include gas flow passages (not shown) through which external air and oxygen that has passed through the cells 5 circulate.

By the way, in this embodiment, as shown in FIG. 1, gas permeability (a ventilation function) was provided between the electrode 3 and the outer gas diffusion layer 8 and between the electrode 4 and the outer gas diffusion layer 9. Heat reflection layers 6 and 7 are provided.
These heat reflection layers 6 and 7 are disposed so as to be in close contact with the electrodes 3 and 4, and reflect and retain the radiant heat of the cell 5 operating at a temperature of approximately 400 to 800 ° C. Since it is necessary to act so that 5 is always kept at a suitable operating temperature, a material having excellent emissivity and heat resistance is used.

FIG. 2 shows a first embodiment of the heat reflecting layers 6 and 7. In this embodiment, the thin plate 20 (that is, the porous metal layer 20) made of Ag or Au provided with a large number of small holes 21 is heated. The reflective layers 6 and 7 are used. These Ag and Au are excellent in heat resistance (high-temperature oxidation resistance), and have excellent emissivity (radiation rate) at the operating temperature of the cell. In the present embodiment, the emissivity of the surface of the metal plate is specified to be at least 0.1 or less, preferably 0.05 or less, so that an excellent heat retaining action by the heat reflecting layers 6 and 7 can be obtained.
Incidentally, the emissivity on the polished surface of Ag or Au material is about 0.03 at a temperature around 500 ° C.

FIG. 3 shows a second embodiment of the heat reflecting layers 6 and 7. In this embodiment, a porous metal layer 20 made of Ag or Au as shown in FIG. As shown in b), the porous metal layer 20 has a two-layer structure in which a porous glass layer 22 (electrical insulating layer 22) is bonded. In this case, it is desirable to arrange the glass layer 22 so as to face the gas diffusion layers 8 and 9.
As described above, by providing the glass layer 22 on one surface of the porous metal layer 20, in the configuration in which the heat reflecting layers 6 and 7 are used as a feeding electrode or a collecting electrode, the emissivity of the metal layer 20 is affected. Can prevent short circuit to other members (gas diffusion layers 8 and 9 and separators 10 and 11) while maintaining good heat radiation effect, thereby improving the reliability of the electrochemical cell 1 it can.

  FIG. 4 shows a third embodiment of the heat reflecting layers 6 and 7. In this embodiment, an Ag layer or an Au layer is formed on one of the porous glass layers 22 by surface treatment. The surface treatment layer 23 made of Ag or Au can be formed by a method such as vapor deposition, sputtering, electroless plating, or powder baking.

  FIG. 5 shows a fourth embodiment of the heat reflecting layers 6 and 7. In this embodiment, the heat reflecting layers 6 and 7 of the first to third embodiments described above and the electrode 3 in contact therewith, 4 is joined by a baking layer 24 of Ag paste or Au paste. In this structure, since the heat | fever reflection layers 6 and 7 and the electrodes 3 and 4 can be joined reliably, the radiant heat from the cell 5 can be suppressed more reliably.

  FIG. 6 shows a fifth embodiment of the heat reflecting layers 6, 7. In this embodiment, scale-like Ag powder or Au powder is applied to the electrodes 3, 4 and / or the gas diffusion layers 8, 9. The heat reflection layers 6 and 7 are formed by baking.

  In the first to fifth embodiments, Ag or Au is used as the material of the metal layer, but Pt, Ir, or an alloy of Au, Ag, Pt, Ir, or the like can be used as another metal material. It is.

  As described above, according to the present invention, by integrally providing the gas permeable heat reflecting layers 6 and 7 outside the electrodes 3 and 4, heat radiation from the cell 5 is suppressed, which contributes to an improvement in thermal efficiency. it can. Thereby, at the time of start-up, the temperature of the cell 5 can be efficiently increased by the heat ray of the attached heating means (not shown), and the electrochemical cell 1 can be rapidly started.

  Further, during operation, the Joule heat generated in the cell 5 by the heat reflecting layer 6 can be efficiently retained, and the cell 5 can be always kept at a suitable operating temperature. Therefore, it is possible to perform a self-sustained operation that maintains the operating temperature of the cell 5 with only the heat generated by itself without adding heat, and this contributes to energy saving.

  In addition, since the heat reflecting layers 6 and 7 are gas permeable, the provision of these heat reflecting layers 6 and 7 does not affect the ventilation performance of oxygen and / or air. In addition, since the heat reflecting layers 6 and 7 are extremely thin and are in close contact with the electrodes 4 and 5, space is not required and the size can be reduced.

  Further, in addition to the heat reflection layers 6 and 7, as shown in FIG. 1, for example, a plating layer 25 made of Ag or Au is formed on the surfaces of the separators 10 and 11, so that the waste from the separators 10 and 11 is wasted. Thermal radiation can be suppressed, and the heat retention effect of the cell 5 by the heat reflecting layers 6 and 7 can be made more reliable.

Sectional drawing which shows the basic composition of the electrochemical cell which concerns on this invention. The figure which shows the structure of the heat | fever reflection layer by 1st Embodiment of this invention. The figure which shows the structure of the heat | fever reflection layer by 2nd Embodiment of this invention. The figure which shows the structure of the heat | fever reflection layer by 3rd Embodiment of this invention. It is principal part sectional drawing of the electrochemical cell which concerns on this invention, and shows the structure of the heat | fever reflection layer by 4th Embodiment. It is principal part sectional drawing of the electrochemical cell which concerns on this invention, and shows the structure of the heat | fever reflection layer by 5th Embodiment. The figure which shows the structure of an oxygen permeable cell. The figure which shows the structure of a hydrogen permeable cell.

Explanation of symbols

1 Electrochemical cell 2 Electrolyte (solid electrolyte)
3 electrodes (cathode)
4 electrodes (anode)
5 cells 6, 7 heat reflective layer 22 electrically insulating layer (glass layer)

Claims (7)

In an electrochemical cell comprising a cell with electrodes on both sides of the electrolyte,
An electrochemical cell characterized in that a heat-reflecting layer having gas permeability is integrally provided outside the electrode. The electrochemical cell according to claim 1, wherein the heat reflection layer includes a porous metal layer made of a metal having a surface emissivity of 0.1 or less. The electrochemical cell according to claim 2, wherein the metal layer is made of Ag or Au. 4. The electrochemical cell according to claim 2, wherein the metal layer is composed of at least one of a thin plate, a vapor deposition layer, a sputtering layer, a plating layer, and a powder baking layer. The electrochemical cell according to any one of claims 1 to 4, wherein an electrically insulating layer is provided on one surface of the heat reflecting layer. The electrochemical cell according to any one of claims 1 to 5, wherein the cell is an oxygen permeable cell using an oxygen ion conductive solid electrolyte as the electrolyte. The electrochemical cell according to any one of claims 1 to 5, wherein the cell is a hydrogen permeable cell using a hydrogen ion conductive solid electrolyte as the electrolyte.

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