Fuel cell, electrolysis cell, and assembled cell

Abstract

To solve a problem of a conventional fuel cell, an electrolytic cell, or the like, in which heat storage and temperature uniformization are not achieved, leading to excessive heat generation or heat reduction due to endothermic reaction, in addition, since the conventional electrolytic cell is significantly deteriorated, and it is also a problem to realize stability to withstand long-term use.SOLUTION: Provided is a fuel cell / electrolytic cell having heat storage or heat equalization function, in which a particulate heat storage or heat equalization material containing a phase change material is disposed.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a fuel cell, electrolysis cell, cell assembly, etc. that can be included in a power generation system, and more particularly to a fuel cell, electrolysis cell, etc. that includes a heat storage or heat equalization material. [Background technology]

[0002] In recent years, renewable energy has been considered essential to realizing the desired carbon-neutral society. However, renewable energy generally has low energy density and large fluctuations in power generation. Therefore, in order to resolve and level out the imbalance in supply and demand of renewable energy, it is necessary to store and level out renewable energy.

[0003] From this perspective, electrolytic cells and the like are used, which generate hydrogen with high efficiency when power is supplied from renewable energy sources. Meanwhile, power generation is also being carried out using fuel cells such as solid oxide fuel cells (SOFCs). Power generation systems that reversibly combine these electrolysis and power generation reactions are known, and one example is a power generation system equipped with a reversible fuel cell module that has an electrolysis function that generates combustible gas when power is supplied from renewable energy sources, and a fuel cell function that generates electricity from the combustible gas (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0004] Patent document 1: WO2015 / 063170 publication Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, in recent years, there has been growing expectation for power generation systems that enable reversible operation of power generation and electrolysis using fuel cells and the like, but conventional fuel cells and the like have significant temperature non-uniformity during operation, and problems such as performance degradation and accelerated device deterioration have arisen due to the occurrence of heat spots, etc. For example, while it is expected that high energy conversion efficiency and energy storage efficiency can be achieved by using conventional solid oxide cells that function as fuel cells and high-temperature electrolysis cells, problems arise in that heat is generated when operated as a fuel cell, which can result in excessive heat, while an endothermic reaction occurs when performing steam electrolysis, which can result in a heat shortage. In other words, conventional fuel cells and electrolysis cells do not store heat or achieve uniform temperature distribution, resulting in problems caused by excessive heat generation or heat loss due to endothermic reactions. On the other hand, electrolysis cells still suffer from significant degradation, and realizing a stable cell that can withstand long-term use is also a challenge. [Means for solving the problem]

[0006] The present invention includes, for example, the following. [1] A fuel cell / electrolysis cell with heat storage or heat distribution function, in which particulate heat storage or heat distribution material containing a phase change material is arranged. [2] The fuel cell / electrolysis cell according to [1] above, which comprises a fuel cell capable of reversible operation of power generation and electrolysis. [3] The fuel cell / electrolysis cell according to [1] or [2] above, for example [1] above, wherein the melting temperature of the phase change material is in the range of 500 to 650°C. [4] The fuel cell / electrolysis cell according to any one of the above [1] to [3], for example the above [1], wherein the phase change material has an endothermic peak in the range of 450 to 600°C in DSC measurement. [5] Any of the above [1] to [4], for example the fuel cell / electrolysis cell according to the above [1], which is a solid oxide fuel cell or electrolysis device comprising an oxygen ion conductor or proton conductor as an electrolyte. [6] A cell assembly including at least the fuel cell or electrolysis cell according to any one of the above [1] to [5], for example, the above [1], in which the heat storage or heat equalization material is installed inside or outside. [7] A heat storage or isothermal material for a fuel cell / electrolysis cell according to any one of [1] to [5] above, for example, the heat storage or isothermal material according to [1] above, characterized in that the phase change material covered by the outer shell is a heat storage or isothermal material containing an aluminum alloy and is electrically insulated by the outer shell. [8] The heat storage or heat equalizing material for a fuel cell / electrolysis cell according to [7] above, wherein the outer shell comprises any one of alumina, aluminum nitride, silicon nitride and silicon carbide. [9] A power generation system having any of the above [1] to [5], for example, the fuel cell / electrolysis cell according to the above [1], or the combined cell according to the above [6].

[10] A method for suppressing temperature changes in a cell, in which a heat storage or isothermal material is placed in contact with the fuel cell / electrolysis cell to suppress temperature changes due to heat generation or absorption by the fuel cell / electrolysis cell.

[11] The temperature change suppression method according to

[10] above, wherein the internal temperature difference during operation of the fuel cell / electrolysis cell is within 20°C. [Effects of the Invention]

[0007] In the present invention, a heat storage or heat release medium is combined with a fuel cell or electrolysis cell, and the temperature of the cell during operation can be easily and reliably adjusted. For example, in a solid oxide cell surrounded by a heat storage material or a heat equalization material, heat handling becomes possible, and the temperature during operation of the cell can be made uniform and long-term stability can be improved.

[0008] In the fuel cell / electrolysis cell of the present invention, excess internal heat is stored in a heat storage material, making it possible to adjust the temperature to maintain an appropriate level even when the operation mode is changed and an endothermic reaction is occurring, and localized heat spots can be removed during heat generation, allowing the reversible operation of the cell to proceed easily and reliably. Furthermore, such a fuel cell / electrolysis cell is less susceptible to heat-related degradation and is expected to have improved long-term stability. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an outline of the manufacturing process of heat storage / radiation particles and the high-speed airflow impact device. [Figure 2] FIG. 1 is a diagram showing an SEM image of the heat storage / radiation particles used in the examples in a state before use. [Figure 3] 1 is a graph showing the results of differential scanning calorimetry of various heat storage / radiation particles. [Figure 4] FIG. 1 is a diagram schematically showing a cell in which a heat storage / heat distribution material is arranged. [Figure 5] FIG. 2 is a diagram schematically showing a cylindrical cell and the like used in the examples. [Figure 6] FIG. 2 is a diagram schematically illustrating cells and current collecting lines in an example and a comparative example. [Figure 7] 1 is a graph showing power generation curves of cells of an example and a comparative example. [Figure 8] 1 is a graph showing impedance plots of cells of an example and a comparative example. [Figure 9] 1 is a graph showing the temperature dependence of the IV / IP curve of the cell of the example. [Figure 10] 1 is a graph showing the analysis results of the internal resistance of the cell of the example by the impedance method. [Figure 11] 1 is a graph showing IV curves in steam electrolysis of cells of an example and a comparative example. [Figure 12] 1 is a graph showing impedance plots of cells of an example and a comparative example. [Figure 13] 1 is a graph showing the results of a comparison test of the SOFC performance and the SOEC performance of the cell. [Figure 14(a)] 1 is a graph showing the time-voltage relationship in an SORC test up to 100 cycles using the cell of Comparative Example 1. [Figure 14(b)] 1 is a graph showing the time-voltage relationship in SORC testing up to 100 cycles for the cell of Example 1. [Figure 15]1 is a graph showing the time-voltage relationship during one cycle and the temperature distribution within the cycle for an example and a comparative example. [Figure 16] 1 is a graph showing impedance plots of cells before and after 100-cycle SORC measurements of Examples and Comparative Examples. [Figure 17] FIG. 1 is a diagram showing an SEM image of the heat storage / radiation particles used in the examples after use. [Figure 18] 1 is a graph showing the results of XRD measurements of the PCM powder of the example before and after testing. [Figure 19] 1 shows SEM images of the cross section and surface of the electrodes of an example and a comparative example after 100 cycles of SORC testing. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following exemplary embodiments. In this specification, "A to B" (A and B are numerical values) means "greater than or equal to A and less than or equal to B."

[0011] <1. Fuel cell / electrolysis cell> 1-1.Cell types The fuel cell / electrolysis cell of the present invention includes various types of cells used as fuel cells or electrolysis devices. For example, the fuel cell / electrolysis cell includes a fuel cell cell, an electrolysis cell, and a combination cell thereof. The fuel cell / electrolysis cell preferably includes a fuel cell capable of reversible operation of power generation and electrolysis. Examples of fuel cells include, but are not limited to, polymer electrolyte fuel cells (PEFCs), phosphoric acid fuel cells (PAFCs), molten carbonate fuel cells (MCFCs), and solid oxide fuel cells (SOFCs), with preferred examples including SOFCs from the standpoint of operating temperature. The types of SOFCs are also not limited to, but include oxide ion conductive ceramic fuel cells and proton conductive ceramic fuel cells, with preferred examples including proton conductive ceramic fuel cells.

[0012] The electrolytic cell is not particularly limited, but examples thereof include alkaline water electrolysis cells, solid polymer water electrolysis cells, and steam electrolysis cells, and preferred specific examples thereof include high-temperature steam electrolysis cells and intermediate-temperature steam electrolysis cells (SOECs). SOECs are preferred specific examples from the viewpoint of operating temperature, etc. The cells to which the present invention is applied may also be, for example, fuel cells in home cogeneration systems, etc. In this case, for example, in the endothermic reaction of obtaining hydrogen from methane and water, the heat stored in the heat storage material described below can be effectively utilized.

[0013] The cell configuration in a specific example of a preferred embodiment will be described below using a solid oxide fuel cell as an example. 1-2. Electrolyte layer The electrolyte in the fuel cell / electrolysis cell preferably contains an oxygen ion conductor or a proton conductor. First, the electrolyte layer formed of an oxygen ion conductor will be described below. In an oxide-ion conducting SOFC that uses an oxygen ion conductor as the electrolyte, the material of the electrolyte layer is not particularly limited as long as it is a material that can conduct ions such as oxide ions generated by the electrode reaction at the oxygen electrode. Among these, the material of the electrolyte layer is preferably a material represented by the following composition formula (1) (LSGM) or YSZ (YO-stabilized ZrO): La 1-s Sr s Ga 1-t Mg t O 3-d (0.05 <s<0.25、0.05<t<0.25) …(1) In the above composition formula (1), La represents lanthanum, Sr represents strontium, Ga represents gallium, Mg represents magnesium, and O represents oxygen. Also, in the above composition formula (1), 1-s represents the atomic ratio of La, s represents the atomic ratio of Sr, 1-t represents the atomic ratio of Ga, t represents the atomic ratio of Mg, and 3-d represents the atomic ratio of O. In the above compositional formula (1), s represents a real number satisfying the relationship 0.05 < s < 0.25, and t represents a real number satisfying the relationship 0.05 < t < 0.25.

[0014] Here, in the above compositional formula (1), when s is a real number satisfying the relationship 0.05 < s < 0.25, the oxide ion conductivity of the electrolyte tends to be excellent when the electrolyte of the solid oxide fuel cell is formed using the metal oxide powder represented by the compositional formula (1). When s represents a real number of 0.25 or more, the content of Sr in the electrolyte becomes too large, other phases are formed, and the oxide ion conductivity of the electrolyte tends to decrease.

[0015] Also, in the above compositional formula (1), when t is a real number satisfying the relationship 0.05 < t < 0.25, the oxide ion conductivity of the electrolyte tends to be excellent when the electrolyte of the solid oxide fuel cell is formed using the metal oxide powder represented by the compositional formula (1). When t represents a real number of 0.25 or more, the content of Mg in the electrolyte becomes too large, other phases are formed, and the oxide ion conductivity of the electrolyte tends to decrease.

[0016] Hereinafter, the electrolyte layer in a proton-conducting SOFC using a proton-conducting material as the electrolyte will be described. The electrolyte made of a proton-conducting material is preferably a perovskite-type oxide, and has a dense layer to prevent gas cross-leakage, and the entire electrolyte may be a dense body. The relative density of the dense layer of the electrolyte may be 90 to 100% by volume, and the thickness of the dense layer of the electrolyte may be 0.1 μm to 300 μm. In order to make the electrolyte thin while preventing gas cross-leakage, it is desirable that the entire electrolyte is a dense body.

[0017] The proton-conducting material of the electrolyte can be an oxide represented by the following formula (2), or a mixture or solid solution of the oxides represented by the following formula (2). A 2 a B 2 b C 2 cO 3-δ2 Formula (2) In the above formula (2), A 2 represents at least one element selected from the group consisting of barium (Ba), calcium (Ca), and strontium (Sr). In the above formula (2), B 2 represents at least one element selected from the group consisting of cerium (Ce) and zirconium (Zr). In the above formula (2), C 2 represents at least one element selected from the group consisting of yttrium (Y), ytterbium (Yb), erbium (Er), holmium (Ho), thulium (Tm), gadolinium (Gd), indium (In), and scandium (Sc). In particular, B 2 is preferably yttrium (Y), which results in higher proton conductivity in the electrolyte.

[0018] In the above formula (2), a can be 0.85 to 1, more preferably 0.88 to 0.98, and even more preferably 0.90 to 0.97. When a is 0.85 or more, high proton conductivity is exhibited. Furthermore, when a is 1 or less, chemical stability is improved. In the above formula (2), b can be 0.50 or more and less than 1, more preferably 0.70 to 0.95, and even more preferably 0.75 to 0.90. When b is 0.50 or more, precipitation of a phase that inhibits proton conduction can be suppressed. Furthermore, when b is less than 1, the conductivity of the electrolyte is further increased. In the above formula (2), c can be a number that satisfies 1-b. In the above formula (2), δ is the amount of oxygen deficiency, which is determined depending on the values ​​of a and b and the atmosphere.

[0019] The proton-conducting material of the electrolyte is Ba, among the compounds represented by formula (2). d Zr e Ce f Y 1-e-f O3-δ3 (where d is a number satisfying 0.85≦d≦1, e is a number satisfying 0≦e≦1, f is a number satisfying 0≦f≦1, δ3 is the amount of oxygen vacancy, and e and f cannot be 0 at the same time) is more preferable.

[0020] The thickness of the electrolyte is not particularly limited, and may be, for example, about 3 μm or more and 100 μm or less. By making the thickness of the electrolyte 3 μm or more, it is possible to increase the strength and prevent gas leakage. Furthermore, by making the thickness of the electrolyte 100 μm or less, it is possible to reduce the resistance. From these viewpoints, the thickness of the electrolyte is more preferably 4 μm or more and 50 μm or less, and even more preferably 5 μm or more and 30 μm or less. The electrolyte may be formed in multiple layers using multiple types of materials.

[0021] 1-3. Electrode The electrodes in the fuel cell / electrolysis cell are selected appropriately depending on the type of cell, etc. First, a preferred embodiment of an electrode in an oxygen ion conducting SOFC will be described below. The fuel electrode is not particularly limited as long as it is made of a material that can emit electrons by reacting with ions such as oxide ions that have been conducted through the electrolyte, and can be made of a porous metal substrate such as a Ni-Fe alloy. The thickness of the fuel electrode can be, for example, 200 μm to 3000 μm.

[0022] A reaction suppression layer for suppressing the reaction between the electrolyte and the anode may be provided between the electrolyte and the anode. The reaction suppression layer is not particularly limited as long as it is made of a material that can suppress the reaction. For example, it is preferably made of a material (SDC) represented by the following composition formula (3):

[0023] Sm y Ce 1-y O 2-(y / 2) (0≦y<0.5) …(3) In the above composition formula (3), Sm represents samarium, Ce represents cerium, and O represents oxygen. In addition, y represents the atomic ratio of Sm, 1-y represents the atomic ratio of Ce, and 2-(y / 2) represents the atomic ratio of O. Here, in the above composition formula (3), when y is a real number that satisfies 0≦y<0.5, the metal oxide in the reaction suppression layer tends to maintain a fluorite-type crystal structure, which tends to further improve the performance of the solid oxide fuel cell.

[0024] The oxygen electrode is, for example, SSC (Sm 0.5 Sr 0.5 CoO 3-d The oxygen electrode can be produced by, for example, a conventionally known citric acid method using SSC powder. The oxygen electrode is preferably formed on the surface of the electrolyte layer.

[0025] Next, a preferred embodiment of an electrode for a proton-conducting SOFC will be described. (air electrode) In a preferred embodiment, the air electrode (cathode) is provided on the opposite side of the electrolyte from the fuel electrode, and air or oxygen gas, etc., can be supplied to the air electrode during operation of the fuel cell. Any conventionally known material can be used for the air electrode, as long as it has catalytic function, electronic conductivity, gas permeability, stability under high-temperature conditions, etc. The material for the air electrode is not particularly limited, but examples include lanthanum strontium cobalt iron composite oxide (LSCF), lanthanum strontium manganese composite oxide (LSM), lanthanum strontium cobalt composite oxide (LSC), lanthanum strontium iron composite oxide (LSF), samarium strontium cobalt composite oxide (SSC), and barium lanthanum cobalt composite oxide (BLC). The thickness of the air electrode can be adjusted depending on the application of the oxide proton conducting fuel cell.

[0026] (Fuel electrode) In a preferred embodiment, the fuel electrode (anode) is located on the opposite side of the electrolyte from the air electrode, and hydrogen gas and the like can be supplied during operation of the fuel cell. Any conventionally known material can be used for the fuel electrode, as long as it has catalytic activity for redox reactions, electronic conductivity, gas permeability, and stability under high-temperature conditions. The material for the fuel electrode is not particularly limited, but may include, for example, nickel (Ni), palladium (Pd), platinum (Pt), ruthenium (Ru), Ni-Fe alloy, Ni-Co alloy, Fe-Co alloy, Ni-Cu alloy, Pd-Pt alloy, a mixture of nickel and zirconia-based oxide, a mixture of nickel and ceria-based oxide, and a mixture of nickel and barium zirconate-based oxide. Furthermore, a small amount of manganese and cerium oxide or cerium oxide may be added to the fuel electrode. The thickness of the fuel electrode can be adjusted depending on the application of the oxide proton conducting fuel cell.

[0027] <2. Cell Group> The cell assembly of the present invention includes at least one of a fuel cell and an electrolysis cell, and other types of cells are not particularly limited. For example, the cell assembly may include either a fuel cell or an electrolysis cell and another cell, and preferably includes both a fuel cell and an electrolysis cell.

[0028] <3. Heat storage material / heat equalization material> In cells such as fuel cells and electrolysis cells, it is preferable that a heat storage material or a heat isotropy material is contained to provide a heat storage or heat isotropy function. It is more preferable that a heat storage / heat isotropy material capable of both heat storage and heat isotropy is used in the cells, and it is preferable that the heat storage material or heat isotropy material contains a phase change material. Furthermore, a particulate material containing a phase change material is preferably used as the heat storage / heat isotropy material. The heat storage / heat isotropy material will be described below.

[0029] 3-1. Core particle The particulate heat storage material or heat isotropy material includes, for example, core particles. The core particle component is preferably Al (aluminum) or an alloy containing Al. The alloy containing Al is preferably an alloy containing Al as the main component. In this specification, the term "main component" refers to a proportion of the entire core particle of 50 mass % or more. As the core particle, it is preferable to use a phase change material (PCM) that can utilize the latent heat of solid-liquid phase change.

[0030] The core particle preferably contains, as a main component, an element (e.g., a metal element) that is more easily oxidized than the dopant described below. Preferred components of the core particle include Al or an alloy of Al with Cu, Si, Zn, or the like. The Cu content in the core particle is not particularly limited as long as it is more than 0% by mass and less than 100% by mass based on the total weight of the core particle. For example, the Cu amount can be in the range of 10% by mass or more and 90% by mass or less, and the Cu content may be 10% by mass or more and 25% by mass or less. The Si content in the core particles is not particularly limited as long as it is more than 0% by mass and less than 100% by mass based on the total weight of the core particles. For example, the Si amount can be in the range of 10% by mass or more and 90% by mass or less, and the Si content may be 10% by mass or more and 25% by mass or less. In addition, the contents of secondary components other than Al, such as Zn, can also be set as described above.

[0031] The average particle size of the core particles is preferably 10 μm or more and 200 μm or less. The average particle size of the core particles is more preferably 15 μm or more and 150 μm or less, even more preferably 20 μm or more and 100 μm or less, and particularly preferably 25 μm or more and 50 μm or less. According to this embodiment, latent heat storage particles having a size on the order of microns and having core particles (PCM) containing the above components can be realized. The "average particle size" referred to in this specification is a value measured using a laser diffraction particle size distribution analyzer (e.g., HORIBA LA-920). More specifically, the volume distribution of the particle group is measured using the laser diffraction particle size distribution analyzer, and the cumulative 50% by volume diameter (D50) is defined as the average particle size.

[0032] In the particles of the heat storage / dissipation material according to this embodiment, the core particles preferably contain one or more elements from Groups 1 to 15 as a dopant, which is different from Al or an alloy containing Al. The dopant contained in the core particles can, for example, serve as a heterogeneous nucleation site during solidification of the PCM, thereby modifying the PCM constituting the core particles and changing its temperature characteristics. As a result, for example, supercooling during temperature reduction in the heat storage cycle, which occurs in particles of conventional heat storage / dissipation materials, can be suppressed, enabling precise control of the solid-liquid temperature hysteresis. As described above, the dopant is not limited to an element that forms an alloy or compound with the components of the core raw material particle, as long as it is incorporated into the core and serves as a heterogeneous nucleation site during solidification of the PCM. For example, if the core particle is composed of an Al-Si alloy, "different from the contained Al or alloy containing Al" refers to one or more elements from Groups 1 to 15 other than Al and Si.

[0033] The dopant is preferably one or more elements selected from the group consisting of Ti, Zr, V, B, Ni, Si, Mn, Cr, Zn, P, Fe, Co, Pb, Cu, Na, and Sr. From the viewpoint of further suppressing supercooling of the heat storage / dissipation material particles, one or more elements selected from the group consisting of Ti, Zr, V, B, and Ni are more preferred, and Ti is particularly preferred.

[0034] The dopant is preferably an element whose standard free energy of formation of the oxide at temperatures between 880°C and 1230°C is higher than the standard free energy of formation of Al2O3. Such an element is preferred because during heat treatment, the child particles of the oxide, which is the raw material for the dopant, are easily reduced by Al in the core raw particle, making it easier for the dopant to be incorporated into the core particle. Note that the standard free energy of formation ΔG of Al2O3 is0 is expressed as the following formula (5) in the oxidation reaction of Al below, where T in formula (5) represents temperature (°C). 4 / 3Al(l) + O2(g) = 2 / 3Al2O3(s) ΔG 0 =-1126890+218.81T(J)···(5)

[0035] The content of the dopant contained in the particles of the heat storage / dissipation material may be, for example, in the range of more than 0 mass % and not more than 5 mass %, which is not more than the proportion of the added child particles.

[0036] The presence of dopants contained in heat storage / dissipation particles can be confirmed by EDS analysis (energy dispersive X-ray spectroscopy) of the cross section of the heat storage / dissipation particle. The dopant inside the core particle can exist as a compound with the components of the core particle. It is believed that by forming a compound in this way and bringing the dopant and core particle components into contact, it becomes easier to control the hysteresis temperature. If the dopant is located inside or outside the coating, it is thought that there is no effect from including the dopant, and hysteresis temperature control is not possible.

[0037] 3-2. Outer shell (coating) The coating may be made of any electrically insulating material, preferably a compound layer with high thermal conductivity. It is preferably an oxide film, nitride, or carbide containing Al. Examples of oxide films containing Al include α-Al2O3, β-Al2O3, and θ-Al2O3. Examples of nitrides include AlN (aluminum nitride) and Si3N4 (silicon nitride), and examples of carbides include SiC (silicon carbide).

[0038] The coating of the particles of the heat storage and dissipation material according to this embodiment may have a thickness in the range of 10 nm to 3 μm. The coating may be, for example, a coating layer with a thickness of 1 to 2 μm. The thickness of the outer shell (coating) is not particularly limited depending on the material, but for example, an oxide coating containing Al may have a thickness in the range of 10 nm to 3 μm, or may be 500 nm to 2.5 μm, 700 nm to 2.2 μm, or 1.0 μm to 2.0 μm, etc.

[0039] The coating portion of the particles of the heat storage and dissipation material according to this embodiment may cover at least a portion of the surface of the core particle. The coverage of the coating portion on the surface of the core particle is preferably 50 area% or more. The coverage is more preferably 70 area% or more, even more preferably 80 area% or more, even more preferably 90 area% or more, and most preferably 100 area%.

[0040] In this embodiment, it is preferable to use particles of the heat storage / radiation material described above as the heat exchange material. The particles of the heat storage / radiation material according to this embodiment may constitute at least a part of the heat exchange material, and examples of the heat exchange material include a form in which the heat storage / radiation material particles are dispersed and contained in a thermal base material, and a form in which the heat storage / radiation material particles are dispersed and supported in a porous material. Examples of heat exchange materials include, but are not limited to, heat storage bricks, heat storage ceramic balls, and porous ceramic filters.

[0041] 3-3. Manufacturing method of heat storage and heat dissipation material particles A preferred method for producing the heat storage / dissipation material particles in this embodiment is (i) preparing a core raw material particle whose component is Al or an alloy containing Al, and a child particle whose component is an oxide of one or more elements selected from Groups 1 to 15, which is different from the Al or alloy containing Al; (ii) subjecting the core material particles and the child particles to collision in a high-speed airflow impact method to hybridization in which the child particles are fixed to the surfaces of the core material particles, thereby obtaining hybridization-treated particles; (iii) performing a chemical conversion coating treatment on the hybridization-treated particles to obtain chemical conversion-coated particles; and (iv) The chemical conversion coated particles are subjected to a heat treatment at 880°C or more and 1230°C or less.

[0042] Specific examples of the process of introducing a dopant into core particles by the above-mentioned manufacturing method will be described using schematic drawings, but the manufacturing method according to this embodiment is not limited to this. Furthermore, the manufacturing method of the particles of the heat storage and dissipation material according to this embodiment is not limited to the method shown in the schematic drawings, and they can also be manufactured by other methods.

[0043] FIG. 1 is a schematic diagram illustrating the manufacturing process of heat storage / dissipation particles 10A in which Cu is introduced as a dopant 21 into core particles 22 (mainly composed of Al). Note that the components in FIG. 1 differ from their actual sizes and amounts. In manufacturing the heat storage / dissipation particles, core raw material particles and child particles for dopant insertion are first prepared as raw material particles. As shown in FIG. 1(a), child particles (CuO particles) 9A are collided with core raw material particles 8 using a high-velocity airflow impact method. As shown in FIG. 1(b), hybridization-treated particles 25 are obtained in which child particles (CuO particles) 9A are fixed to the surfaces of core raw material particles 8. Next, the hybridization-treated particles 25 are subjected to a chemical conversion coating treatment to obtain chemically coated particles 26 in which a chemical conversion coating 24 is formed on the surfaces of core raw material particles 8, as shown in FIG. 1(c). The chemical conversion-treated particles 26 are then heat-treated. FIG. 1(d) is a diagram showing a particle at an early stage of heat treatment, and the dashed line portion is an enlarged schematic cross-sectional view of a portion of the particle near its surface.

[0044] As shown in the enlarged cross-sectional schematic diagram of Figure 1(d), during the heat treatment, it is believed that Cu, a component of child particles (CuO particles) 9A present on the surface of core raw material particle 8, is reduced by Al, a component constituting core raw material particle 8, and the resulting Cu is incorporated into the core raw material particle. As a result, as shown in Figure 1(e), it is believed that heat storage / dissipation material particle 10A is obtained in which Cu is present as dopant 21 within core particle 22 and is coated with an α-Al2O3 film, which is an oxide film 23 of Al, a component of the core particle. Each step will be described in detail below.

[0045] (i) Preparation of raw material particles As raw material particles, core raw material particles and child particles for dopant insertion are prepared. The core raw material particles may have an average particle diameter of, for example, 10 μm or more and 200 μm or less, corresponding to the core particles of the desired heat storage / heat dissipation material particles. The average particle diameter may be, for example, 100 μm or less, or even 50 μm or less. The average particle diameter of the child particles is preferably 0.1 μm or more and 2 μm or less, and the ratio (average particle diameter of child particles / average particle diameter of core raw material particles) is preferably 0.001 or more and 0.2 or less. The average particle diameter of the child particles may be 1.0 μm or less, or even 0.4 μm or less. The components of the core raw material particles are the same as those of the core particles of the heat storage / heat dissipation material particles, and are as described above for the components of the core particles of the heat storage / heat dissipation material particles.

[0046] The component of the child particles is an oxide of one or more elements from Groups 1 to 15 that is different from the Al or Al-containing alloy contained therein. Preferred elements constituting the oxide are as described above for the dopant of the latent heat storage particles, and the component of the child particles is preferably an oxide of one or more elements selected from the group consisting of Ti, Zr, V, B, Ni, Si, Mn, Cr, Zn, P, Fe, Co, Pb, Cu, Na, and Sr. More preferably, the component is an oxide of one or more elements selected from the group consisting of Cu, Ti, Zr, V, B, and Ni, and particularly, oxides of Cu and Ti such as CuO and TiO2 are preferred.

[0047] The blending ratio of core material particles and child particles fed into the device can be set such that the ratio of child particles to (core material particles + child particles) is in the range of 0.5% by mass or more and 10% by mass or less. The above ratio is preferably 1.0% by mass or more. From the viewpoint of facilitating the chemical conversion coating treatment described below, the above ratio is preferably 8% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. The above ratio is preferably, for example, in the range of 1.0% by mass or more and 5% by mass or less.

[0048] (ii) Hybridization of core particles and daughter particles by impact in high-speed airflow In this embodiment, core raw particles and daughter particles for forming the coating portion are used, and the daughter particles are mechanically struck against the surface of the core raw particle using a high-speed airflow impact method, followed by a dry mechanical method to obtain hybridization-treated particles in which the daughter particles are adhered to the surface of the core raw particle. The "adhesion" mentioned above includes physical adhesion due to changes in the shape of the daughter particles, as well as adhesion due to a chemical reaction between the core raw particle and the daughter particles. The degree of adhesion of the daughter particles is not limited, as long as at least a portion of the surface of the core particle is coated.

[0049] Hereinafter, the high-velocity air current impact method used in the manufacturing method according to this embodiment will be described using the high-velocity air current impact device shown in FIG. 1(f), but the present invention is not limited to this embodiment.

[0050] 1(f) is a schematic cross-sectional view of a high-velocity airflow impact device 100 for carrying out hybridization by the high-velocity airflow impact method. The high-velocity airflow impact device 100 is equipped with a raw material particle inlet 1, a high-speed rotating rotor 2, blades 3, a stator 4, a circulation circuit 5, a discharge valve 6, and a discharge port 7.

[0051] In the high-velocity airflow impact method, first, powder core raw material particles 8 and fine powder child particles 9 are fed into the impact chamber through a sample inlet 1. Then, as the rotor 2 rotates, the core raw material particles 8 and child particles 9 in the impact chamber are scattered while rotating at high speed within the impact chamber, during which time the child particles 9 collide with the surfaces of the core raw material particles 8. Some of the raw material particles enter one connection port of a circulation circuit 5 connected to the collision chamber, circulate, and are then introduced back into the collision chamber through the other connection port. This circulation circuit 5 allows repeated collision processing of the core raw material particles 8 and child particles 9. By continuing this rotational collision for a certain period of time, the child particles 9 adhere to the surfaces of the core raw material particles 8, and furthermore, the child particles 9 are deformed to form latent heat storage particles 10. During the collision between the core raw material particles 8 and the child particles 9, the introduction path to the outlet 7 is closed by the discharge valve 6, but after a certain time, the obtained latent heat storage particles 10 pass through the introduction path to the outlet 7 that is opened by moving the discharge valve 6, and are discharged to the outside of the device from the outlet 7. Although not shown, a cooling water passage may be provided to prevent the temperature inside the collision chamber from becoming too high, and the collision process may be performed while cooling by flowing cooling water.

[0052] The peripheral speed of the rotor 2 in the above-mentioned device can be, for example, 40 m / s or more and 120 m / s or less, preferably in the range of 80 to 100 m / s. The treatment time depends on the treatment amount, but can be, for example, 1 to 20 minutes, preferably 3 to 10 minutes. The treatment temperature can be, for example, in the range from room temperature to 70°C, and further in the range from room temperature to 50°C. The pressure and atmosphere of the collision chamber are not particularly limited. The atmosphere of the collision chamber can be, for example, an inert gas atmosphere such as an Ar atmosphere.

[0053] (iii) Chemical conversion coating The hybridization-treated particles are subjected to a chemical conversion coating treatment. This results in chemically coated particles having a chemical conversion coating on their surfaces that contains the constituent elements of the core raw material particles. The chemical conversion coating treatment is not limited as long as it is a method of oxidizing the surface of Al or an Al alloy to form a dense Al oxide or Al hydroxide coating. Examples of chemical conversion coating treatment methods include the boehmite method, phosphate chromate treatment method, chromate chromate treatment method, and zinc phosphate treatment method. The boehmite method is preferred.

[0054] The boehmite process is a treatment specified in "JIS H 0201:1998 Terminology for Aluminum Surface Treatment," and is a method for forming a coating on the surface of aluminum in high-temperature distilled water or a weak alkaline aqueous solution. It has been confirmed that the higher the pH value of the boehmite treatment solution, the better the quality of the resulting Al oxide coating. In particular, it is preferable to set the pH value in the range of 6.0 or higher but less than 9.0, more preferably 7.0 to 8.5, and most preferably 8.0. The boehmite treatment can be performed at a temperature of 80°C to 100°C for 0.25 to 3 hours. The treatment is preferably performed while stirring.

[0055] (iv) Heat treatment (calcination) The chemically coated particles can be heat-treated to oxidize the chemical conversion coating of the chemically coated particles and form an oxide coating as a coating portion. The heat treatment temperature can be, for example, higher than the melting point of the metal (including alloy) that constitutes the core raw material particles, e.g., 700°C to 1300°C. The aluminum oxide film formed by heat treatment takes the γ-Al2O3 crystal form at relatively low temperatures of approximately 800°C or less, while a chemically stable α-Al2O3 film can be obtained at relatively high temperatures of approximately 880°C or more. For example, to obtain a chemically stable α-Al2O3 film, the heat treatment temperature is preferably 880°C to 1230°C. The heat treatment temperature is more preferably 900°C to 1230°C.

[0056] The atmosphere for the heat treatment is not particularly limited. Examples include air atmosphere or oxygen atmosphere created by supplying oxygen gas to a heat treatment furnace. The temperature inside the furnace is increased using a heater, and once the sample temperature reaches a predetermined temperature, heat treatment (oxidation treatment) is performed for, for example, 1 to 5 hours to obtain heat-treated latent heat storage particles. The heat treatment method can be, for example, to fill the chemically coated particles into a crucible, place the crucible on top of a thermocouple attached to the tip of an insertion rod, and set it in a heat treatment furnace equipped with a heater. Figure 2 shows an example of an SEM image of the heat storage / isotrace material particles immediately after production.

[0057] 3-4. Composition and properties of heat storage and heat equalization material particles As is clear from the above-mentioned manufacturing method, the phase change material contained as the core particle in the heat storage / heat equalizing particle preferably has aluminum as its main component, and is preferably an aluminum-silica alloy, an aluminum-copper alloy, an aluminum-copper-silica alloy, an aluminum-titanium alloy, an aluminum-titanium-silica alloy, etc. In addition, the outer shell of the heat storage / heat equalizing particle preferably has alumina as its main component. Such heat storage and heat dissipation materials containing such heat storage and heat equalization particles as the main component are preferably electrically insulated, and are suitable for use in fuel cells, electrolysis cells, and cell assemblies containing at least one of these.

[0058] The heat storage and heat equalizing particles preferably have an average particle size of 1 to 200 μm, more preferably 5 to 120 μm, even more preferably 10 to 80 μm, and particularly preferably 20 to 50 μm.

[0059] The phase change material contained in the heat storage / equalizing material particles preferably has a latent heat quantity of 100 to 500 kJ / kg, more preferably 150 to 400 kJ / kg, further preferably 200 to 350 kJ / kg, and particularly preferably 260 to 300 kJ / kg.

[0060] The phase change material contained in the heat storage and heat distribution particles has a latent heat density of 0.3 to 2.0 GJ / m 3 The latent heat density of the phase change material is preferably 0.5 to 1.5 GJ / m 3 More preferably, it is 0.7 to 1.2 GJ / m 3 More preferably, it is 0.8 to 1.0 GJ / m 3 It is particularly preferred that:

[0061] The phase change material contained in the heat storage / equalizing material particles preferably has an endothermic peak in a range of 450 to 600°C in DSC measurement, more preferably in a range of 500 to 550°C, and even more preferably in a range of 520 to 540°C.

[0062] The phase change material contained in the heat storage / heat equalizing particles preferably has a melting temperature of 500 to 650° C. The melting temperature is more preferably 510 to 630° C., and even more preferably 520 to 600° C. For example, the melting temperatures of various heat storage / heat release particles, including the heat storage / heat equalizing particles used in the examples, are 520 to 530° C., as shown in the differential scanning calorimetry results in FIG.

[0063] <4. Methods for suppressing temperature changes in cells> The above-described heat storage and isotropic material can be used to suppress temperature changes due to heat generation or heat absorption during operation of fuel cells, electrolysis cells, assembled cells, etc., primarily temperature changes due to heat generation. The heat storage and isotropic material is preferably placed in direct contact with the fuel cells, electrolysis cells, etc., but may be placed at a distance of, for example, 5 cm or less, 3 cm or less, or 1 cm or less from the cell. Furthermore, the heat storage and isotropic material is preferably placed either outside or inside the cell, and more preferably outside or inside the cell. The heat storage and isotropic material may be placed on either the air electrode side or the fuel electrode side of the cell, and is preferably placed on both the air electrode side and the fuel electrode side.

[0064] In a fuel cell / electrolysis cell incorporating a heat storage / heat equalization material, it is preferable to suppress the internal temperature difference during operation to within 50°C or 20°C. The temperature difference during operation of the fuel cell / electrolysis cell is preferably 10°C or less, and more preferably 5°C or less. The temperature difference during operation of the cell is the difference between the maximum and minimum temperatures during operation, and the cell temperature is measured by a known method.

[0065] <5. Examples of cells and power generation systems> Specific examples of cells include fuel cells and electrolysis cells incorporating a heat storage and equalizing material, and assembled cells including both. For example, a cell 40 shown schematically in FIG. 4 is an assembled cell 30 including both a fuel cell and an electrolysis cell, with a heat storage and equalizing material 32 disposed around the periphery. In this manner, the heat storage and equalizing material 32 is preferably disposed so as to cover at least a portion of the periphery of the fuel cell, electrolysis cell, or the like, and is preferably disposed so as to cover substantially the entire periphery of the cell, for example, the entire side surface on which no terminals are provided (see FIG. 4). In the cell assembly 40 exemplified in FIG. 4, it is preferable that a heat storage / heat equalizing material is disposed inside either the fuel cell or the electrolysis cell, and preferably both.

[0066] In fuel cells, electrolysis cells, combined cells, etc. that contain such a heat storage material and heat isotropy material, the operating temperature range of the cell is not particularly limited, but is, for example, 300 to 1000°C, preferably 400 to 800°C, more preferably 400 to 700°C, 450 to 750°C, etc., and particularly preferably 450 to 650, 500 to 600°C, 500 to 650°C, 500 to 700°C, 550 to 650°C, etc. By using fuel cells, electrolysis cells, or cell assemblies containing heat storage and isothermal materials, the operating temperature of a power generation system can be easily and reliably adjusted within a suitable range. Furthermore, deterioration of these electrolysis cells over long-term use can be prevented, achieving excellent stability. [Example]

[0067] The present invention is not limited to the following examples, and modifications of the examples as appropriate may also be included within the technical scope of the present invention.

[0068] 1. Manufacturing Example 1: Manufacturing of heat storage and heat dissipation material (PCM) A particulate heat storage / dissipation material was manufactured using core raw material particles and child particles as follows. First, core raw material particles, which were an Al alloy containing 5.4 mass% Si and 26.5 mass% Cu (Al-26.5mass%Cu-5.4mass%Si), and child particles containing TiO2 were prepared. The average particle size of the core raw material particles was 37 μm, and the average particle size of the child particles was 0.5 μm.

[0069] The blending ratio of core raw material particles and daughter particles was adjusted so that the ratio of daughter particles to the total of core raw material particles and daughter particles was 3% by mass. Then, using a high-speed airflow impact device manufactured by Nara Machinery Manufacturing Co., Ltd., processing was performed at a peripheral velocity of 80 m / s for 3 minutes. In this way, the daughter particles were collided with the core raw material particles by the high-speed airflow impact method, and hybridization-treated particles were obtained.

[0070] Next, the hybridization-treated particles were placed in a beaker containing distilled water, and the distilled water was heated to 100°C on a hot plate. The surfaces of the hybridization-treated particles were treated with boehmite for 3 hours while stirring with a stirring rod, to obtain chemically coated particles.

[0071] The chemically coated particles were then loaded into a crucible, which was then placed on top of a thermocouple attached to the tip of an insertion rod and placed in a heat treatment furnace equipped with a heater. In this heat treatment furnace, the temperature of the chemically coated particles was gradually increased in either the air or an oxygen atmosphere formed by supplying oxygen gas through the gas inlet of the heat treatment furnace and guiding the exhaust gas to the outside through the gas outlet. Once the temperature reached 1000°C, the particles were subjected to heat treatment (oxidation treatment) for 3 hours, yielding samples with an α-Al2O3 film formed on the surface of the chemically coated particles as heat storage / dissipation materials.

[0072] (SEM observation) The appearance of the hybridization-treated particles obtained in Production Example 1 was observed using an SEM (JEOL, JSM-7001FA), confirming that the daughter particles were adhered almost uniformly to the surface of the core raw material particles. Furthermore, SEM observations of the chemically coated particles obtained in Production Example 1 and the samples (heat storage / dissipation materials) were also performed. The results confirmed that all of the chemically coated particles had a petal-like structure characteristic of the boehmite shell. Furthermore, even after heat treatment above the melting point of Al-26.5 mass% Cu-5.4 mass% Si, no leakage of the PCM was observed in any of the samples, and the spherical shape was maintained (Figure 2). Thus, the production of microencapsulated heat storage / dissipation materials was confirmed.

[0073] (XRD measurement) XRD measurements were carried out under the following conditions for the hybridization-treated particles produced in Production Example 1, the chemically coated particles obtained by chemically coating the hybridization-treated particles, and the sample (heat storage / dissipation material) obtained by heat-treating the chemically coated particles. The results confirmed that the main peaks in the sample (heat storage / dissipation material) were derived from Al, Si, Cu, and α-Al2O3. (Measurement conditions) X-ray diffractometer: X-ray diffractometer XRD Rigaku MiniFlex600 X-ray source: Cu line Detector: High-speed one-dimensional detector D / teX Ultra2 Tube voltage: 40kV ·Tube current: 15mA Scan speed: 1.0° / min Step: 0.01°

[0074] (Differential Scanning Calorimetry (DSC)) Using the sample obtained in Production Example 1, differential scanning calorimetry was performed using a differential scanning calorimeter (manufactured by Mettler Toledo, model number: 823e). Specifically, using an alumina pan, differential scanning calorimetry was performed during temperature drop (heat release side) under conditions of a temperature drop rate of 5 K / min from 800°C to 400°C in an Ar atmosphere. The resulting DSC curve is shown in Figure 3. From the results in Figure 3 and elsewhere, it can be seen that the latent heat of the fine particles of the heat storage and release material is approximately 260 to 300 kJ / kg, and the latent heat density converted to latent heat density is approximately 0.8 to 1.0 GJ / m 3 and the melting temperature was confirmed to be approximately 520°C.

[0075] 2. Manufacturing Example 2: Cell Creation A NiO-YSZ tubular support cell was fabricated as follows. An extruded NiO-YSZ green tube (13 mm diameter, 30 mm length) manufactured by Chiba Ceramic Industry Co., Ltd. was prepared. This was then subjected to a dip-coating process. First, NiO and YSZ powders were mixed with a binder and a dispersant, pre-fired at 1373 K, and then extruded to form a NiO-YSZ porous substrate. The NiO-YSZ porous substrate thus obtained was dip-coated to form a Ni-Fe conductive layer (twice), a Ce conductive layer (30 mm length), and a NiO-YSZ porous substrate (30 mm length). 0.6 Mn 0.3 Fe 0.1 O2 layer (CMF, once), 0.5wt%TiO2 mixed Ce 0.6 La 0.4 O2 layer (Ti-LDC, once), La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O3 (LSGM, 15 times) electrolyte layer was fabricated. 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ(LSGM) powder was synthesized by a solid-state reaction method. Furthermore, precursors of stoichiometric ratios of La2O3 (Kishida, 99.99%), SrCO3 (RareMetallic, 99.99%), Ga2O3 (Wako, 99.99%), and MgO (Wako, 99.9%) were ball-milled with ethanol for 24 hours using a planetary ball milling mixer equipped with 10 mm diameter ZrO2 balls and a ZrO2 pot (volume: 100 ml). After calcination at 1373 K, the mixture was ball-milled again to obtain powders with small particle sizes for application. NiO-Fe2O3 (9:1 wt%) powder was prepared by the conventional impregnation method.

[0076] Ce 0.6 Mn 0.3 Fe 0.1 O 2-δ (CMF) and 0.5wt% TiO2-added Ce 0.6 La 0.4 O 2-δ (Ti-LDC) as a buffer layer, and Sm 0.5 Sr 0.5 CoO 3-δ (SSC) was used as the air electrode. Ball-milled CMF powder, LDC powder, and SSC powder were calcined at 1273 K, 1623 K, and 1473 K, respectively. Next, all synthesized powders were dispersed in a 2-propanol solution to prepare a dip-coating slurry. Also, a LSGM slurry containing 15 wt% cellulose was prepared to apply a porous LSGM functional layer to the air electrode side. The prepared powder was mixed with polyvinyl butyral (PVB) as a binder and dispersed in a 2-propanol solvent to prepare a dip-coating slurry. The prepared half-cell was co-sintered at 1633 K for 3 hours, and finally, dip-coated with SSC slurry to form the cathode, which was then fired at 1373 K. The diameter of the co-sintered NiO-YSZ was 10.5 mm, and the length of the dip-coated cathode layer was 10 mm. The effective electrode area of ​​the cell was 3.3 cm2. Then, as shown in Figure 5(a), a cylindrical cell 48 containing an anode 42, electrolyte 44, and cathode 46 was filled with 0.32 g of PCM powder (heat storage / dissipation material) 50 (described below) prepared in advance, and one side was sealed with quartz wool (not shown). Quartz wool was also filled in the other side, and the cell was inverted to check for PCM powder leakage, completing the preparation of the LSGM. Note that in Figure 5, arrow (i) indicates the fuel flow, and arrow (ii) indicates the air flow. Furthermore, instead of the cylindrical cell 48 in FIG. 5(a), a flat cell 54 in FIG. 5(b) further having an interconnector 52 may be used to evaluate and put the cell into practical use.

[0077] 3. Examples 1 and 2 A plurality of cells were manufactured using the method of Manufacturing Example 2, and samples of Examples and Comparative Examples were prepared which differed in the built-in PCM powder, substrate, etc. First, the encapsulated particles of the heat storage and release material obtained in Manufacturing Example 1 were built into the cells of Manufacturing Example 2 as PCM powder to prepare the cell sample of Example 1. Next, a cell sample of Example 2 was prepared by the same method as in Example 1, except that the NiO-YSZ substrate of Production Example 2 was subjected to Ce infiltration treatment.

[0078] 4. Comparative Examples 1 and 2 The cell sample of Comparative Example 1 differed from the cell sample of Example 1 only in that no PCM powder was used. Furthermore, the cell sample of Comparative Example 2 differed from the cell sample of Example 1 only in that Al2O3 beads (corresponding only to the outer shell of the PCM powder) were used as the PCM powder instead of the capsule-shaped particles of the heat storage and heat release material of Production Example 1.

[0079] 5. Cell Electrochemical Measurements The tubular LSGM cells of the examples and comparative examples were subjected to electrochemical measurements as follows.

[0080] (Power generation curve) First, two LSGM cells from Example 1 were covered with a platinum (Pt) mesh for current collection. Two Pt lines on the SSC positive electrode and two Pt lines on the internal NiO-YSZ substrate were connected to the Pt mesh to form current collection lines for power density measurement (Figure 6). Pyrex glass melted at 1073 K and glass paste were used as the sealant between the single-tube cell and the Al2O3 support tube. After confirming there was no gas leakage, the cell was reduced with humidified H2 at 973 K for 1 hour. The power generation characteristics of the single cell in SOFC mode were then measured at 773-873 K using a four-probe method. The steam electrolysis performance of the cell was also tested at 773-873 K using a 50% steam-10% H2 mixture in Ar (100 cc / min). The SSC electrodes were exposed to the open air. The concentration of the supplied steam was calculated from the saturated vapor pressure by adjusting the temperature of the water in the tank of the evaluation vessel.

[0081] The applied current to the cell was controlled with a galvanostat (HAL-3001, Hokuto Denko), and the terminal voltage was monitored with a digital multimeter (R6451A, Advantest). During the durability test, the applied current was controlled and the potential change was recorded using an electrochemical measurement system (HZ-7000, Hokuto Denko). A commercially available humidifier system (Minitest 3000, Toyo Technica) was used to supply and control the vapor. The amount of H2 produced was measured with a gas chromatograph (GC-8A, Shimadzu). Complex impedance analysis of the cell's internal resistance was performed using an impedance / gain-phase analyzer (Type 1260, Solartron) equipped with an electrochemical interface (Solatron Type 1287, Solartron). The cell's ultrastructure and elemental distribution were analyzed using a field-emission scanning electron microscope (FE-SEM, Versa 3D, FEI) equipped with an EDX detector (Oxford).

[0082] Figure 7 shows the power generation curves for cells using four types of NiO-YSZ tubes: Examples 1 and 2, and Comparative Examples 1 and 2. The open-circuit potential for all four examples is around 1.1 V, which is somewhat close to the theoretical value. However, the power generation density is high in Example 1, which incorporates a PCM material, and Example 2, which employs Ce infiltration, and is low in Comparative Example 1, which does not incorporate a PCM, and Comparative Example 2, which employs only Al2O3 beads.

[0083] Furthermore, the power generation density of the cell in Example 2, in which PCM powder was packed into a Ce-infiltrated Ni-YSZ tube substrate, appears to be particularly high. The power generation density of the cell in which PCM powder was packed into a Ce-infiltrated Ni-YSZ tube substrate was 0.806 W / cm² at 873 K. The power density of the cell in Comparative Example 1, which used a NiO-YSZ substrate without Ce infiltration and no PCM material, was 0.38 W / cm². In comparison, the power density of the cell packed with a Ce-infiltrated PCM was 2.1 times higher. Furthermore, the maximum power densities of the cell in Example 1, which contained only PCM powder, and the cell in Comparative Example 2, which contained only Al2O3 beads, were 0.65 and 0.40 W / cm², respectively. This study demonstrated that the incorporation of PCM material has a significant positive effect on the power density of SOFCs. This is thought to be due to the removal of high-resistance areas such as heat spots by the heat dissipation from the PCM material, thereby reducing internal resistance.

[0084] (Impedance plot (i)) Figure 8 shows the impedance plots for the four cells of the example and comparative examples under open-circuit conditions in SOFC mode. It was found that the impedance semicircle in the figure is composed of at least two semicircles: one at a high frequency and the other at a low frequency, similar to the Warburg impedance. Therefore, it can be seen that the IR loss and overvoltage can be reduced in the case of a cell in which a PCM is packed into a NiO-YSZ tube substrate.

[0085] Furthermore, in the case of the cell in Example 2, in which a PCM material was packed onto a Ce-infiltrated Ni-YSZ substrate, IR loss was significantly reduced, and the introduction of numerous oxygen vacancies reduced activation overpotential and concentration overpotential. Furthermore, in Comparative Example 2, in which only Al2O3 beads were embedded, the Al metal homogenized the temperature, slightly increasing the average temperature and eliminating heat spots, resulting in a slight reduction in IR loss and overpotential. The impedance semicircle at low frequencies was reduced, suggesting that the introduction of an AlSi alloy-based PCM is effective in increasing power density by improving gas diffusivity in the NiO-YSZ porous substrate. Therefore, cells using NiYSZ tube substrates embedded with PCM material exhibit higher power density due to reduced cell overpotential and IR loss.

[0086] (Temperature dependence of power generation characteristics) The cell of Example 2, infiltrated with 1.5MCe, was filled with a PCM material and its power generation characteristics were evaluated. The temperature dependence of the IV / IP curve of this cell is shown in Figure 9. The maximum power densities at operating temperatures of 873K, 823K, and 773K were 0.806, 0.304, and 0.104W / cm, respectively. 2 It was confirmed that the cell has excellent power generation performance. Ce infiltration confirmed many vacancies in the CeO2, and it is presumed that the generation of CeO2 nanoparticles with many oxygen defects resulted in a reduction in IR loss. Furthermore, the introduction of the Al-Si alloy PCM material significantly reduced the temperature gradient of the cell, and since both of these factors contribute to heat dissipation, and the temperature was higher than the actual set temperature, as shown in Figure 10, IR loss decreased with overvoltage, resulting in a high power density. The power density was significantly increased thanks to the double positive effect of Ce infiltration and the introduction of the PCM material.

[0087] (Steam electrolysis) Since a large effect was observed in the SOFC mode, the effect of introducing a PCM in steam electrolysis was also investigated. Figure 11 shows a comparison of the IV curves of cells using the four substrates of each example and comparative example, at 873 K and in an Ar atmosphere of 10% H2-50% H2O (total 100 cm3). 3 / min). As with the SOFC, the electrolysis current of the cell changed significantly with the infiltration of Ce and the introduction of PCM materials. The electrolysis performance of the cell without PCM was 0.45 A / cm at 1.6 V. 2 The electrolysis current of the cell without PCM material and the cell without Ce infiltration PCM material was 0.86 A / cm at 1.6 V, respectively. 2 and 1.09A / cm 2 Figure 12 shows the impedance plots for each cell. The impedance plots for each cell consist of at least two semicircles, which are thought to be due to the activation overpotential and concentration overpotential in the high-frequency and low-frequency regions, respectively. Both the IR and the overpotential were clearly reduced by the introduction of PCM materials.

[0088] (SOFC・SOFC performance comparison) Figure 13 summarizes a comparison of the SOFC and SOEC performance of the four cells of each Example and Comparative Example at 873 K. In both cases, when a PCM material was introduced, roughly twice the performance was obtained compared to a cell without a PCM material. Furthermore, in Example 2, in which a PCM material was introduced into a Ce-infiltrated NiYSZ tube substrate, even higher performance was confirmed. The introduction of a PCM material was confirmed to have a very excellent effect on the initial characteristics of cells using NiOYSZ tube substrates.

[0089] (SORC test) Similar to Example 1 and Comparative Example 1, SORC tests were performed up to 100 cycles using cells with and without PCM. The measurement temperature was 873 K, and the time-voltage relationship is shown in Figure 14. As shown in Figure 14(a), in Comparative Example 1, which did not incorporate a PCM material, the initial OCV was 0.956 V, and the voltages during the first SOEC and SOFC tests were 1.18 V and 0.731 V, respectively. After 5 cycles, the voltages during the SOEC and SOFC tests were 1.14 V and 0.685 V, respectively. The time-voltage relationship for cycles 91-100 is shown in the graph on the lower right. The OCV decreased to 0.916 V, and the voltages during the 100th SOEC and SOFC tests were 1.16 V and 0.675 V, respectively. It was also confirmed that the magnitude and number of noises increased compared to the initial state. The degradation rates up to 100 cycles were 0.02V / 100 cycles and 0.01V / 100 cycles for the SOEC and SOFC tests, respectively. The degradation rate in the SOEC test was greater than that in the SOFC test. This indicates that the SOFC test exhibits superior activity.

[0090] On the other hand, in Example 1 (Figure 14(b)), in which a PCM material was used, the initial OCV was 0.948 V, and after 5 cycles, the voltages during the SOEC and SOFC tests were 1.048 V and 0.852 V, respectively. The time-voltage relationship for cycles 91-100 is shown in the graph on the lower right, where the OCV was 0.946 V and the voltages during the 100th SOEC and SOFC tests were 1.053 V and 0.848 V, respectively. The degradation rates up to 100 cycles were 0.005 V / 100 cycles and 0.004 V / 100 cycles for the SOEC and SOFC tests, respectively. By incorporating a PCM, the degradation rate after 100 cycles was minimal, demonstrating excellent stability.

[0091] (Cell temperature change curve) The time-voltage relationship during one cycle and the temperature distribution within the cycle are shown in Figure 15. The cell of Comparative Example 1 without PCM is shown in Figure 15(a). For the SOEC & SOFC mode, the current density was 0.1 A / cm2 The graph on the right shows the temperature distribution of the cell. In SOEC mode, the temperature rose when switching from OCV. Once the cell was fully in SOEC mode, the temperatures at the top, center, and bottom remained nearly constant, with the center being the highest. The temperature at the top, where the gas enters, was slightly lower, while the temperature at the bottom was slightly higher. All temperatures were below 600°C or above 595°C. When switching from SOEC mode to SOFC mode, the temperature dropped instantly. Once the cell was fully in SOFC mode, the center temperature exceeded 600°C. Both the top and bottom temperatures were higher than those in SOFC mode. When switching from SOEC mode to OCV, the temperature dropped, and the temperature drop at the center was smaller. In Example 1, which contains PCM powder, the temperature rose by 40°C (Figure 15(b)). The temperature gradient of the cell was reduced in both modes.

[0092] (Impedance plot (ii) / Stability of heat storage and heat dissipation materials) Figure 16 shows the impedance plots of cells in Example 1 and Comparative Example 1, which differ in the presence or absence of PCM powder, before and after 100-cycle SORC tests at 873 K. Comparing the impedance spectra before and after the tests, the IR loss is estimated by the intercept on the x-axis. It can be seen that the cell in Comparative Example 1 (Figure 16(a)), which lacks a PCM, exhibits a slightly larger impedance after the tests. Furthermore, although the impedance arcs in the high-frequency region become larger after the 100-cycle SORC test, the magnitude of the impedance arcs did not increase significantly, except for a slight increase in impedance in the low-frequency region, which is thought to be due to diffusion overpotential. Since Ni reoxidation is another issue that contributes to SOEC performance degradation due to increased ohmic loss, the XRD of the Ni-YSZ porous substrate after the 100-cycle SORC test is shown in the lower panel of Figure 16. All diffraction peaks are due to Ni and YSZ, and no diffraction peaks due to NiO were detected. Therefore, Ni reoxidation did not occur in any of the substrates under the 10% H2-50% H2O conditions.

[0093] Figure 17 shows the results of SEM observation of the PCM material after the SORC test. The heat storage material, which consists of an Al-Si alloy (PCM) packed into ceramic capsules, has a spherical shape. It was confirmed that the state of the capsules remained almost unchanged after the test compared to before the test (Figure 2). Figure 18 shows the results of XRD measurements of the PCM powder before and after the test. These results confirmed that picks of other composites of Al and Si picks were also observed, and all had similar XRD patterns. It was confirmed that the PCM powder remained in a very stable state.

[0094] For each cell in Example 1 and Comparative Example 1, which differed in the presence or absence of a PCM, SEM observations of the cross section and surface were performed after 100 cycles of SORC testing. SEM images of the electrodes taken are shown in Figure 19. The cross-sectional images revealed that a dense LSGM electrolyte membrane approximately 50 μm thick was formed in all cases, and no delamination was observed between the individual layers or between the membrane and the Ni-YSZ substrate. Furthermore, images of the SSC electrode confirmed that the membrane remained porous in all cases. Excellent mechanical strength and electrode material stability were also observed after 100 cycles of SORC testing.

[0095] As described above, in the cells of the examples using PCM as a heat storage and temperature equalization material, heat storage and temperature uniformity were achieved, and temperature changes due to excessive heat generation were suppressed. Furthermore, the results showed that the stability of the cells in the examples was superior to that of the comparative examples.

Claims

1. A fuel cell / electrolysis cell having a heat storage or heat distribution function, in which a particulate heat storage or heat distribution material containing a phase change material is disposed.

2. 10. The fuel cell / electrolysis cell of claim 1, comprising a fuel cell capable of reversible operation for electricity generation and electrolysis.

3. 2. The fuel cell / electrolysis cell of claim 1, wherein the phase change material has a melting temperature in the range of 500 to 650°C.

4. 2. The fuel cell / electrolysis cell of claim 1, wherein the phase change material has an endothermic peak in the range of 450 to 600° C. in DSC measurement.

5. 10. The fuel cell / electrolysis cell of claim 1 as a solid oxide fuel cell or electrolyzer, comprising an oxygen ion conductor or proton conductor as an electrolyte.

6. 10. A cell assembly comprising at least the fuel cell or electrolysis cell according to claim 1, the heat storage or isothermal material being installed inside or outside the cell.

7. A heat storage or isothermal material for a fuel cell / electrolysis cell as described in claim 1, characterized in that the phase change material covered with an outer shell is a heat storage or isothermal material containing an aluminum alloy and is electrically insulated by the outer shell.

8. 8. The thermal storage or isolating material for a fuel cell / electrolysis cell according to claim 7, wherein the outer shell comprises one of alumina, aluminum nitride, silicon nitride and silicon carbide.

9. A power generation system comprising the fuel cell / electrolysis cell according to any one of claims 1 to 5 or the combined cell according to claim 6.

10. A method for suppressing temperature changes in a cell, comprising arranging a heat storage or isothermal material in contact with the fuel cell / electrolysis cell to suppress temperature changes due to heat generation or absorption by the fuel cell / electrolysis cell.

11. 11. The temperature change suppression method according to claim 10, wherein the internal temperature difference during operation of the fuel cell / electrolysis cell is within 20°C.

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