Metal-air battery

Abstract

The present invention provides a metal-air battery that can maintain charge / discharge performance for a long period of time with a simpler configuration and fewer manufacturing steps. The metal-air battery 10 includes a fuel cell 12, a fuel material body 14, and a joint body 16. The joint body 16 is disposed between the fuel cell 12 and an airtight container 16a to join them, and includes glass. The airtight container 16a accommodates the fuel material body 14 in an airtight manner, and the air electrode 12b of the fuel cell 12 is airtightly fixed to a part of its wall in a state where it is exposed to the outside. The fuel cell 12 and the fuel material body 14 are heated and maintained at their respective predetermined temperatures. The glass of the joint body 16 including glass has a crystallization temperature higher than the predetermined temperature of the fuel cell 12. The metal-air battery 10 is manufactured so that the joint body 16 including glass does not exceed the crystallization temperature, and is used in a temperature range in which crystallization of the joint body 16 including glass is not promoted.

Description

[Technical field]

[0001] The present invention relates to a metal-air battery which is capable of charging as well as discharging, and in particular to a metal-air battery which uses metal powder such as iron powder to regenerate fuel gas within the system. [Background technology]

[0002] A fuel cell is a means of generating electricity by supplying fuel gas to a power generator. Among fuel cells, solid oxide fuel cells (SOFCs), which use an inorganic solid electrolyte with oxygen ion conductivity, are known to be clean and highly efficient power generating devices. Metal-air batteries have also been developed that have a mechanism for restoring fuel gas consumed by the discharge of the fuel cell and can be used as secondary batteries. Furthermore, technology has been developed to prevent leakage of fuel gas in order to prevent a decrease in charge / discharge performance when the consumption and restoration of fuel gas is repeated over a long period of time.

[0003] Patent Document 1 describes a metal-air battery having a flat electrode composite, a negative electrode fuel material, and a metallic sealed container, which is provided with a glass membrane that covers an oxide layer formed on at least one of the outer and inner surfaces of the sealed container in order to improve hydrogen permeation suppression performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6865993 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, an oxide layer must be formed between the surface of the sealed container and the glass film, which makes the structure complicated. In addition, the sealed container must be fired in air to form the oxide layer, which increases the number of manufacturing steps.

[0006] The present invention has been made in consideration of the above-mentioned problems in the conventional art, and an object of the present invention is to provide a metal-air battery that has a simpler configuration and requires fewer manufacturing steps and is capable of maintaining charge / discharge performance for a long period of time. [Means for solving the problem]

[0007] That is, a first aspect of the present invention is a metal-air battery comprising a fuel cell having an air electrode, which reduces oxygen in the air to oxygen ions during discharge, on one surface of a solid oxide film that conducts oxygen ions, and an anode, which oxidizes hydrogen gas to water vapor by the oxygen ions during discharge, on the other surface; a fuel material body that reacts with water vapor to generate hydrogen gas and becomes an oxide itself; and an airtight container in which the fuel material body is airtightly contained, the airtight container having the air electrode of the fuel cell airtightly fixed to a part of its wall in a state where it is exposed to the outside, and a joint including glass disposed between the fuel cell and the airtight container for joining the fuel cell and the airtight container, the fuel cell and the fuel material body being heated and maintained at their respective predetermined temperatures, the glass of the joint including glass has a crystallization temperature higher than the predetermined temperature of the fuel cell, the metal-air battery is manufactured so that the joint including glass does not exceed the crystallization temperature, and the metal-air battery is mainly used in a temperature range in which crystallization of the joint including glass is not promoted. The predetermined temperature of the fuel cell is 450 to 800°C, and the crystallization temperature of the glass is 820 to 900°C. The present invention provides a metal-air battery that uses

[0008] A second embodiment of the present invention is a metal-air battery comprising a fuel material which reacts with water vapor to produce hydrogen gas and which itself becomes an oxide, a first internal space in which the fuel material is hermetically contained, and a second internal space constituted by a flat fuel cell and a main body, the fuel cell and the main body being hermetically joined by a joint containing glass arranged between them, the second internal space being constituted by a fuel cell which reacts with water vapor to produce hydrogen gas and which itself becomes an oxide, a first internal space in which the fuel material is hermetically contained and which is provided with an air electrode on one surface of a solid oxide film which conducts oxygen ions, the air electrode reducing oxygen in the air to oxygen ions during discharge, and a fuel electrode which oxidizes hydrogen gas to water vapor by the oxygen ions during discharge, the second internal space being constituted by a fuel cell and a main body, the fuel cell and the main body being hermetically joined by a joint containing glass arranged between them, the second internal space being further constituted by a flow path arranged between them for communicating the first internal space and the second internal space, the metal-air battery being manufactured so that the joint containing glass does not exceed its crystallization temperature, and the metal-air battery being mainly used in a temperature range in which crystallization of the joint containing glass is not promoted. The predetermined temperature of the fuel cell is 450 to 800°C, and the crystallization temperature of the glass is 820 to 900°C. The present invention provides a metal-air battery that uses Effect of the Invention

[0010] The metal-air battery of the present invention can maintain charge / discharge performance for a long period of time with a simpler configuration and fewer manufacturing steps. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing a metal-air battery according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing a fuel cell constituting the metal-air battery of FIG. 1 and its periphery. [Diagram 3] FIG. 2 is a cross-sectional view showing a metal-air battery according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The metal-air battery of the present invention will be described in detail below with reference to the preferred embodiments shown in the accompanying drawings. First, a first embodiment of the metal-air battery of the present invention will be described. Fig. 1 is a cross-sectional view showing the first embodiment of the metal-air battery of the present invention, and Fig. 2 is a cross-sectional view showing a fuel cell constituting the metal-air battery of Fig. 1 and its periphery.

[0013] The metal-air battery 10 includes a fuel cell 12, a fuel material 14, and a joint 16. The fuel cell 12 includes an air electrode 12b on one surface of a solid oxide membrane 12a that conducts oxygen ions, and an anode 12c on the other surface. The air electrode 12b reduces oxygen in the air to oxygen ions during discharge. The anode 12c oxidizes hydrogen gas to water vapor by the oxygen ions during discharge. The fuel material 14 reacts with water vapor to generate hydrogen gas, and becomes an oxide itself. The joint 16 is disposed between the fuel cell 12 and the airtight container 16a to join them, and includes glass. The airtight container 16a airtightly contains the fuel material 14, and the air electrode 12b of the fuel cell 12 is airtightly fixed to a part of its wall in a state where it is exposed to the outside. The fuel cell 12 and the fuel material 14 are heated and maintained at their respective predetermined temperatures. The glass of the glass-containing assembly 16 has a crystallization temperature higher than the predetermined temperature of the fuel cell 12. The metal-air battery 10 is manufactured so that the glass-containing assembly 16 does not exceed its crystallization temperature, and is used in a temperature range in which crystallization of the glass-containing assembly 16 is not promoted. The cover 16b is preferably disposed between the outer surface of the airtight container 16a and the external environment to insulate the two. By adopting such a configuration, the metal-air battery of the present invention can maintain charge / discharge performance for a long period of time with a simpler configuration and fewer manufacturing steps.

[0014] Next, a second embodiment of the metal-air battery of the present invention will be described below. Fig. 3 is a cross-sectional view showing the second embodiment of the metal-air battery of the present invention. The metal-air battery 30 has a fuel material body 14, a first internal space 32, and a second internal space 34. The fuel material body 14 reacts with water vapor to generate hydrogen gas and becomes an oxide. The first internal space 32 accommodates the fuel material body 14 in an airtight manner. The second internal space 34 is composed of a flat fuel cell 12 and a main body 34a. The fuel cell 12 has an air electrode 12b on one surface of a solid oxide film 12a that conducts oxygen ions, and a fuel electrode 12c on the other surface. The air electrode 12b reduces oxygen in the air to oxygen ions during discharge. The fuel electrode 12c oxidizes hydrogen gas to water vapor by the oxygen ions during discharge. The fuel cell 12 and the main body 34a are airtightly joined by a joint 16 containing glass disposed between them. The metal-air battery 30 further has a flow path 36. The flow path 36 is disposed between the first internal space 32 and the second internal space 34 to communicate with each other. The metal-air battery 30 is manufactured so that the glass-containing joined body 16 does not exceed its crystallization temperature, and is used in a temperature range in which crystallization of the glass-containing joined body 16 is not promoted.

[0015] The fuel section 32a has a first internal space 32 therein. It is preferable that the first covering body 32b is disposed between the outer surface of the fuel section 32a and the external environment, the second covering body 34b is disposed between the outer surface of the main body section 34a and the external environment, and the flow path covering body 36a is disposed between the outer surface of the member constituting the flow path 36 and the external environment, in order to provide thermal insulation between the outer surface of the member and the external environment. By adopting such a configuration, the metal-air battery of the present invention can maintain charge / discharge performance for a long period of time with a simpler configuration and fewer manufacturing steps.

[0016] Next, the fuel material constituting the metal-air battery of the present invention will be described. The fuel material body 14 is not particularly limited as long as it reacts with water vapor to generate hydrogen gas and becomes an oxide itself, but is preferably a pellet-shaped body made of iron particles or iron powder and a shape-retaining material. The shape-retaining material is made of a material that is difficult to sinter or a mixture thereof. Examples of the material that is difficult to sinter are aluminum oxide, silicon dioxide, magnesium oxide, and zirconium oxide. At least a part of the surface of the fuel material body 14 is covered with the shape-retaining material, and the mass ratio of the shape-retaining material to the fuel material body 14 is 0.1% or more and 5% or less. If this mass ratio is less than 0.1%, the surface of the fuel material body 14 may sinter and the oxidation-reduction reaction may not occur, and if it exceeds 5%, the oxidation-reduction rate may be excessively suppressed. The diameter of the pellet is, for example, 2 to 10 mm.

[0017] Next, the operating temperature of the metal-air battery of the present invention will be described. The crystallization temperature of the glass may be 820 to 900°C. In that case, the temperature of the fuel cell 12 may be 450 to 800°C, and the temperature of the fuel material body 14 may be 300 to 1000°C. That is, if the temperature of the fuel cell 12 is less than 450°C or the temperature of the fuel material body 14 is less than 300°C, the metal-air batteries 10 and 30 may not operate. If the temperature of the fuel cell 12 exceeds 800°C or the temperature of the fuel material body 14 exceeds 1000°C, the output may decrease due to the aggregation of the fuel material body 14. In addition, when the temperature inside the airtight container 16a rises from, for example, 22°C to 730°C, the volume does not change, so the internal pressure increases by about 3.4 times according to Boyle's law. Therefore, if the thickness of the fuel cell 12 is the same, the larger the size of the fuel cell 12, the more likely the fuel cell 12 is to be damaged. The same applies to the first internal space 32 and the second internal space 34 that are connected to each other.

[0018] Next, the state of the metal-air battery of the present invention during charging will be described. During charging, the fuel material 14 reacts with hydrogen gas to produce water vapor and becomes a pure metal, the fuel electrode 12c reduces the water vapor to hydrogen gas, the solid oxide film 12a conducts oxygen ions, and the air electrode 12b oxidizes the oxygen ions to oxygen and releases it into the air.

[0019] Next, the state of the metal-air battery of the present invention during discharge will be described. During discharge, the air electrode 12b reduces oxygen in the air to oxygen ions, the solid oxide film 12a conducts the oxygen ions, the fuel electrode 12c oxidizes hydrogen gas to water vapor, and the fuel material 14 reacts with the water vapor to produce hydrogen gas and becomes an oxide itself.

[0020] Next, the effect of gravity on the metal-air battery of the present invention will be described. When the flat fuel cell 12 is arranged vertically, it is necessary to prevent the assembly 16 (if it is liquid and not solid) from moving downward due to gravity. On the other hand, when the flat fuel cell 12 is arranged horizontally, hydrogen gas, water vapor, and nitrogen tend to gather from the top due to gravity, and if left for a long time, the gas molecules will approach a state of being separated into layers. Therefore, in order to supply hydrogen gas to the fuel material 14 during charging and water vapor during discharging, and to supply water vapor to the fuel cell 12 during charging and hydrogen gas during discharging, it is preferable that the vertical length of the internal space of the airtight container 16a, the first internal space 32, and the second internal space 34 is as short as possible. In addition, it is preferable that the first internal space 32 and the second internal space 34 are arranged at the same vertical position (height) as much as possible. Since the flow path 36 generates a pipe resistance, it is preferable that it is as wide and short as possible, and it is preferable that it is arranged horizontally without inclining. Furthermore, if the temperature of the gas in each space is not uniform, convection is likely to occur. Specifically, when the heater is placed above, convection is likely to occur only in the gas above, whereas when the heater is placed below, convection is likely to occur not only in the gas above but in the entire gas. The metal-air battery of the present invention is basically constructed as described above. EXAMPLES

[0021] Next, the present invention will be described in more detail with reference to specific examples. First, as Example 1, a metal-air battery A was produced using glass A. Glass A has a crystallization temperature of 800 to 900° C. and a thermal expansion coefficient of 105 to 115×10 -7 / ℃. Next, as Example 2, a metal-air battery B was produced using glass B. Glass B has a crystallization temperature of 800 to 900° C. and a thermal expansion coefficient of 95 to 105×10 -7 / ℃.

[0022] Next, as Comparative Example 1, a metal-air battery C was produced using glass C. Glass C has a crystallization temperature of 700 to 800° C. and a thermal expansion coefficient of 110 to 120×10 -7 / ℃. Next, as Comparative Example 2, a metal-air battery D was produced using glass D. Glass D has a crystallization temperature of 700 to 800° C. and a thermal expansion coefficient of 90 to 100×10 -7 / ℃.

[0023] <Discharge capacity measurement> As an indicator of whether charge / discharge performance is maintained over a long period of time, the number of repeated charge / discharge cycles under conditions where 90% or more of discharge capacity is maintained was set, with the target range being 10 or more repeated charge / discharge cycles. First, metal-air battery A was charged and discharged in a furnace at 730°C, then cooled to room temperature, and heated again to repeatedly charge and discharge, and the discharge capacity at that time was measured. As a result, metal-air battery A maintained 100% of its discharge capacity until the 30th charge / discharge, which was within the preset target range. Similarly, metal-air battery B was measured, and as a result, metal-air battery B maintained 100% of its discharge capacity until the 10th charge / discharge, which was within the preset target range.

[0024] In contrast, metal-air battery C was similarly measured, and the discharge capacity of metal-air battery C was 0% after the sixth charge / discharge, which was outside the preset target range. Similarly, metal-air battery D was similarly measured, and the discharge capacity of metal-air battery D was 0% after the third charge / discharge, which was outside the preset target range. From these results, it is clear that by constructing a metal-air battery in the same manner as in Examples 1 and 2, it is possible to maintain charge / discharge performance for a long period of time with a simpler configuration and fewer manufacturing steps.

[0025] The metal-air battery of the present invention has been described in detail above with reference to Examples 1 and 2. However, the present invention is not limited to the above description, and various improvements and modifications may be made without departing from the spirit and scope of the present invention. [Industrial Applicability]

[0026] INDUSTRIAL APPLICABILITY The metal-air battery of the present invention has an advantageous effect of being able to maintain charge / discharge performance for a long period of time with a simpler configuration and fewer manufacturing steps, and is therefore industrially useful. [Explanation of symbols]

[0027] 10, 30 Metal-air battery 12 Fuel cell 12a Solid oxide film 12b Air electrode 12c fuel electrode 14 Fuel material body 16 Zygote 16a Airtight container 16b Covering 32 1st interior space 32a Fuel section 32b First covering 34 Second interior space 34a Main body 34b Second covering 36 Flow Path 36a Channel covering

Claims

1. a fuel cell comprising an air electrode, which reduces oxygen in the air to oxygen ions during discharge, on one surface of a solid oxide film that conducts oxygen ions, and a fuel electrode, which oxidizes hydrogen gas to water vapor by the oxygen ions during discharge, on the other surface; a fuel material that reacts with the water vapor to produce the hydrogen gas and that becomes an oxide; the fuel material body is provided with an airtight container in which it is airtightly contained, the airtight container having a part of a wall to which an air electrode of the fuel cell is airtightly fixed with the air electrode exposed to the outside, and a joining body including glass is disposed between the fuel cell and the airtight container to join them, a metal-air battery in which the fuel cell and the fuel body are heated and maintained at respective predetermined temperatures; the glass of the glass-containing bonded body has a crystallization temperature higher than a predetermined temperature of the fuel cell; The metal-air battery is manufactured so that the temperature of the bonded body including the glass does not exceed a crystallization temperature, and the metal-air battery is mainly used in a temperature range in which crystallization of the bonded body including the glass is not promoted; the predetermined temperature of the fuel cell is 450 to 800° C., A metal-air battery, wherein the crystallization temperature of the glass is 820 to 900°C.

2. A fuel substance that reacts with water vapor to produce hydrogen gas and becomes an oxide itself; a first internal space in which the fuel material is hermetically contained; a second internal space constituted by a main body and a flat fuel cell having an air electrode, which reduces oxygen in the air to oxygen ions during discharge, on one surface of a solid oxide film that conducts oxygen ions, and a fuel electrode, which oxidizes hydrogen gas to water vapor by the oxygen ions during discharge, on the other surface of the solid oxide film; A metal-air battery in which the fuel cell and the main body are hermetically joined by a joint containing glass disposed between the fuel cell and the main body, Further, a flow path is disposed between the first internal space and the second internal space to communicate with each other, The metal-air battery is manufactured so that the temperature of the bonded body including the glass does not exceed a crystallization temperature, and the metal-air battery is mainly used in a temperature range in which crystallization of the bonded body including the glass is not promoted; the predetermined temperature of the fuel cell is 450 to 800° C., A metal-air battery, wherein the crystallization temperature of the glass is 820 to 900°C.

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