Symmetric solid oxide fuel cell and method of making and cell stack

Abstract

The present application relates to a symmetrical solid oxide fuel cell, a preparation method thereof and a cell stack. The symmetrical solid oxide fuel cell comprises a first anode current collector layer, a first insulating layer, a second anode current collector layer, a first single cell, a first cathode current collector layer, a second insulating layer, a second cathode current collector layer and a second single cell which are sequentially stacked; the first single cell and the second single cell each independently comprise an anode layer, an electrolyte layer and a cathode layer; the anode layer is provided with flow channels for fuel gas flow which are distributed at intervals on a surface away from the electrolyte layer; the anode layer of the first single cell faces the second anode current collector layer, and the cathode layer of the second single cell faces the second cathode current collector layer; the first anode current collector layer is electrically connected with the first cathode current collector layer, and the second anode current collector layer is electrically connected with the second cathode current collector layer, so as to connect the first single cell and the second single cell in series. The symmetrical SOFC has high raw material utilization rate, large current collecting area and is easy to assemble into a cell stack.

Description

Technical Field

[0001] This invention relates to the technical field of fuel cells, and in particular to a symmetrical solid oxide fuel cell, its preparation method, and its stack. Background Technology

[0002] Solid oxide fuel cells (SOFCs) are all-solid-state energy conversion devices that convert the chemical energy in fuel and oxidant into electrical energy through electrochemical reactions. They have advantages such as a wide range of fuel options, high energy conversion efficiency, low environmental pollution, and modular assembly.

[0003] SOFCs can be classified into three types according to their battery configuration: planar, tubular, and flat-tube. Among them, flat-tube SOFCs typically form an electrolyte layer and a cathode layer sequentially on one surface of the anode layer. Therefore, only half of the anode layer in this type of SOFC participates in the electrochemical reaction, resulting in a relatively low material utilization rate. Summary of the Invention

[0004] Therefore, it is necessary to provide a symmetrical solid oxide fuel cell, its preparation method, and its stack to solve the problem of low raw material utilization in flat-tube SOFCs.

[0005] The above-mentioned objective of this invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a symmetrical solid oxide fuel cell, comprising a first anode current collector, a first insulating layer, a second anode current collector, a first single cell, a first cathode current collector, a second insulating layer, a second cathode current collector, and a second single cell, which are sequentially stacked.

[0007] The first single cell and the second single cell each independently include an anode layer, an electrolyte layer and a cathode layer stacked sequentially; the surface of the anode layer away from the electrolyte layer is provided with spaced-apart flow channels for the flow of fuel gas; the anode layer of the first single cell faces the second anode current collector layer, and the cathode layer of the second single cell faces the second cathode current collector layer.

[0008] The first anode current collector is electrically connected to the first cathode current collector, and the second anode current collector is electrically connected to the second cathode current collector, so as to connect the first single cell and the second single cell in series.

[0009] In one embodiment, one or more of the following conditions are met:

[0010] 1) The thickness of the cathode layer is 1 μm to 100 μm;

[0011] 2) The thickness of the electrolyte layer is 0.1 μm to 100 μm;

[0012] 3) The thickness of the anode layer is 0.01 mm to 5 cm;

[0013] 4) The thicknesses of the first anode current collector, the second anode current collector, the first cathode current collector, and the second cathode current collector are each independently 0.1 mm to 1 cm;

[0014] 5) The thickness of the first insulating layer and the second insulating layer are each independently 0.1 mm to 1 cm.

[0015] In one embodiment, one or more of the following conditions are met:

[0016] 1) The depth of the flow channel is 0.01 mm to 4.99 cm;

[0017] 2) The radial cross-sectional shape of the flow channel is semi-circular, semi-elliptical, or polygonal.

[0018] In one embodiment, one or more of the following conditions are met:

[0019] 1) The raw materials for the cathode layer include ABO3 type perovskite material and a pore-forming agent;

[0020] 2) The raw material for the electrolyte layer includes zirconia-based ceramic materials;

[0021] 3) The raw materials for the anode layer include metal-ceramic composite materials and pore-forming agents;

[0022] 4) The raw materials of the first anode current collector, the second anode current collector, the first cathode current collector, and the second cathode current collector each independently include one or more of iron, copper, chromium, and nickel;

[0023] 5) The raw materials of the first insulating layer and the second insulating layer each independently include one or more of alumina, mica, asbestos, marble, and glass.

[0024] In one embodiment, the symmetrical solid oxide fuel cell further includes a first transmission surface that electrically connects the first anode current collector and the first cathode current collector, and a second transmission surface that electrically connects the second anode current collector and the second cathode current collector.

[0025] In one embodiment, one or more of the following conditions are met:

[0026] 1) The thickness of the first transmission surface and the second transmission surface are each independently 0.1 mm to 1 cm;

[0027] 2) The radial cross-sectional shapes of the first transmission surface and the second transmission surface are each independently circular arcs;

[0028] 3) The raw materials of the first transmission surface and the second transmission surface each independently include one or more of iron, copper, chromium and nickel.

[0029] In a second aspect, the present invention provides a method for preparing a symmetrical solid oxide fuel cell, comprising the following steps:

[0030] An anode layer is formed with spaced channels on its surface for the flow of fuel gas.

[0031] An electrolyte layer is formed on the surface of the anode layer away from the flow channel;

[0032] A cathode layer is formed on the electrolyte layer to obtain a first single cell and a second single cell.

[0033] The first anode current collector and the first cathode current collector are electrically connected, and the second anode current collector and the second cathode current collector are electrically connected.

[0034] The first anode current collector, the first insulating layer, the second anode current collector, the first single cell, the first cathode current collector, the second insulating layer, and the second cathode current collector are stacked sequentially, with the anode surface of the first single cell facing the second anode current collector and the cathode surface of the second single cell facing the second cathode current collector, to obtain the symmetrical solid oxide fuel cell.

[0035] In one embodiment, the step of forming an electrical connection between the first anode current collector and the first cathode current collector, and forming an electrical connection between the second anode current collector and the second cathode current collector includes the following steps;

[0036] The first anode current collector and the first cathode current collector are electrically connected through the first transmission surface;

[0037] The second anode current collector and the second cathode current collector are electrically connected through the second transmission surface.

[0038] In one embodiment, the following steps are also included:

[0039] Prepare a first mixture containing a metal ceramic material and a pore-forming agent, a second mixture containing a zirconia-based ceramic material, and a third mixture containing an ABO3-type perovskite material and a pore-forming agent;

[0040] The first mixture is pressed into shape and subjected to a first calcination to obtain the anode layer;

[0041] The second mixture is applied to the surface of the anode layer away from the flow channel, and then subjected to a second calcination to obtain the electrolyte layer.

[0042] The third mixture is applied over the electrolyte layer and then subjected to a third calcination to obtain the cathode layer.

[0043] In a third aspect, the present invention provides a battery stack comprising a plurality of symmetrical solid oxide fuel cells as described above, arranged in a stacked manner.

[0044] The first and second single-cell designs of this invention both place the flow channels on the surface of the anode layer away from the electrolyte layer, allowing the entire anode layer to participate in the electrochemical reaction and significantly improving the raw material utilization rate of the anode layer. The anode layer of the first single-cell faces the second anode current collector, while the cathode layer of the second single-cell faces the second cathode current collector. Its current collection area is much larger than that of a flat-tube SOFC with a symmetrical dual-cathode structure, which is beneficial for improving the current collection rate and electrochemical performance of the SOFC. Simultaneously, through the electrical connection between the first anode current collector and the first cathode current collector, and the electrical connection between the second anode current collector and the second cathode current collector, the first and second single-cell cells can be directly connected in series, significantly reducing the assembly difficulty of the battery stack. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of a traditional flat-tube SOFC.

[0046] Figure 2 This is a schematic diagram of a flat-tube SOFC with a symmetrical dual-cathode structure in traditional technology.

[0047] Figure 3 This is a three-dimensional structural diagram of a symmetrical SOFC in one embodiment;

[0048] Figure 4 for Figure 3 The front view of the symmetrical SOFC shown;

[0049] Figure 5 This is a flowchart of a method for preparing a symmetric SOFC in one embodiment;

[0050] Figure 6 This is a three-dimensional structural diagram of the battery stack in one embodiment.

[0051] Figure label:

[0052] Cathode layer 11, electrolyte layer 12, anode layer 13, anode current collector layer 14, flow channel 15;

[0053] First cathode layer 211, second cathode layer 212, first barrier layer 221, second barrier layer 222, first electrolyte layer 231, second electrolyte layer 232, anode layer 24, flow channel 25;

[0054] First anode current collector layer 311, first insulating layer 312, second anode current collector layer 313, first single cell 320, first cathode current collector layer 331, second insulating layer 332, second cathode current collector layer 333, second single cell 340, first transmission surface 351, second transmission surface 352, anode layer 361, electrolyte layer 362, cathode layer 363, flow channel 364. Detailed Implementation

[0055] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0056] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0058] In this article, the axial section refers to the section passing through the axis of the geometric body; the radial section refers to the section perpendicular to the axis of the geometric body, that is, the radial section is perpendicular to the axial section.

[0059] SOFCs can be classified according to different criteria such as support components, cell configuration, operating temperature, and material type. Based on the different components that primarily support the cell and maintain its mechanical strength, SOFCs can be divided into anode-supported, electrolyte-supported, and cathode-supported types. Based on the different cell configurations, SOFCs can also be classified into tubular, planar, and flat-tube types.

[0060] Among them, the flat-tube SOFC not only possesses the geometric symmetry characteristics of a tubular structure, overcoming problems such as edge warping, through-cracks, and poor sealing that occur in flat-plate structures during long-term operation, but also has the advantages of simple fabrication methods and high power density of flat-plate structures. Please refer to [link / reference]. Figure 1 This is a schematic diagram of a conventional flat-tube SOFC. The flat-tube SOFC includes a cathode layer 11, an electrolyte layer 12, an anode layer 13, and an anode current collector layer 14 stacked in sequence; wherein, the anode layer 13 serves as the support for a single cell, and has multiple spaced-apart flow channels 15 for the flow of fuel gas inside.

[0061] In the operation of a flat-tube SOFC, oxygen undergoes a reduction reaction on the cathode layer 11 to generate oxygen anions. These oxygen anions are transported to the anode layer 13 via the electrolyte layer 12, where they react with the fuel to generate H2O and CO2, releasing electrons in the process. The anode current collector layer 14 collects the electrons released from the anode layer 13 and transmits them to the external circuit. Therefore, it is evident that only the side of the anode layer 13 facing the electrolyte layer 12 participates in the electrochemical reaction in this flat-tube SOFC, resulting in relatively low feedstock utilization.

[0062] Reports have proposed a method such as Figure 2 The symmetrical dual-cathode SOFC shown includes a first cathode layer 211, a first barrier layer 221, a first electrolyte layer 231, an anode layer 24, a second electrolyte layer 232, a second barrier layer 222, and a second cathode layer 212 stacked sequentially. The anode layer 24 has a flow channel 25 for fuel gas circulation. This flat-tube SOFC forms a symmetrical dual-cathode structure on two opposite surfaces of the anode layer 24 to improve the material utilization rate of the anode layer 24. However, it is difficult to connect the first cathode layer 211, the second cathode layer 212, and the anode layer 24 of two adjacent single cells using a simple circuit, resulting in significant assembly difficulties for the battery stack. Furthermore, this flat-tube SOFC can only set an anode current collector (not shown) on the side of the anode layer 24 to collect electrons released by the anode layer 24. The side area of ​​the anode layer 24 is small, making anode current collection difficult and severely affecting the electrochemical performance of the SOFC.

[0063] Based on this, in a first aspect, the present invention provides a symmetrical solid oxide fuel cell to solve the problems of low raw material utilization, difficulty in anode current collection, and difficulty in assembling into a battery stack that exist in traditional flat-tube SOFCs.

[0064] Please see Figure 3 and Figure 4 ,in, Figure 3 This is a three-dimensional structural diagram of a symmetrical SOFC in one embodiment. Figure 4 for Figure 3The diagram shows a front view of a symmetrical SOFC. This symmetrical SOFC includes a first anode current collector 311, a first insulating layer 312, a second anode current collector 313, a first single cell 320, a first cathode current collector 331, a second insulating layer 332, a second cathode current collector 333, and a second single cell 340, which are sequentially stacked.

[0065] The first single cell 320 and the second single cell 340 each independently include an anode layer 361, an electrolyte layer 362 and a cathode layer 363 stacked sequentially; the surface of the anode layer 361 away from the electrolyte layer 362 is provided with spaced-apart flow channels 364 for the flow of fuel gas; the anode layer 361 of the first single cell 320 faces the second anode current collector 313, and the cathode layer 363 of the second single cell 340 faces the second cathode current collector 333;

[0066] The first anode current collector 311 is electrically connected to the first cathode current collector 331, and the second anode current collector 313 is electrically connected to the second cathode current collector 333, so as to connect the first single cell 320 and the second single cell 340 in series.

[0067] In this invention, both the first single cell 320 and the second single cell 340 have flow channels 364 positioned on the surface of the anode layer 361 away from the electrolyte layer 362, allowing the entire anode layer 361 to participate in the electrochemical reaction and significantly improving the material utilization rate of the anode layer 361. The anode layer 361 of the first single cell 320 faces the second anode current collector 313, while the cathode layer 363 of the second single cell 340 faces the second cathode current collector 333. Its current collection area is much larger than that of a flat-tube SOFC with a symmetrical dual-cathode structure, which is beneficial for improving the current collection rate and electrochemical performance of the SOFC. Simultaneously, through the electrical connection between the first anode current collector 311 and the first cathode current collector 331, and the electrical connection between the second anode current collector 313 and the second cathode current collector 333, the first single cell 320 and the second single cell 340 can be directly connected in series, significantly reducing the assembly difficulty of the battery stack.

[0068] Understandably, the symmetry in symmetrical SOFC refers to the symmetrical distribution of the first single cell 320 and the second single cell 340, or in other words, the first single cell 320 and the second single cell 340 are symmetrically distributed along the plane containing the second insulating layer 332.

[0069] In some implementations, one or more of the following conditions are met:

[0070] 1) The thickness of the cathode layer 363 is 1μm to 100μm;

[0071] 2) The thickness of the electrolyte layer 362 is 0.1 μm to 100 μm;

[0072] 3) The thickness of the anode layer 361 is 0.01 mm to 5 cm;

[0073] 4) The thicknesses of the first anode current collector 311, the second anode current collector 313, the first cathode current collector 331, and the second cathode current collector 333 are each independently 0.1 mm to 1 cm;

[0074] 5) The thickness of the first insulating layer 312 and the second insulating layer 332 are each independently 0.1 mm to 1 cm.

[0075] The thin cathode layer 363 and electrolyte layer 362 have low internal resistance, allowing SOFCs to achieve higher power density at lower operating temperatures. The anode layer 361, with a thickness of 0.01 mm to 5 cm, enhances the mechanical strength of the single cell, improving its structural stability and preventing issues such as edge warping, structural damage, and even cell failure that can occur with thin-layer structures. The thicknesses of the first anode current collector layer 311, the second anode current collector layer 313, the first cathode current collector layer 331, and the second cathode current collector layer 333, ranging from 0.1 mm to 1 cm, also contribute to improving the mechanical strength and lifespan of the battery stack.

[0076] Preferably, one or more of the following conditions are met:

[0077] 1) The thickness of the cathode layer 363 is 1μm to 50μm;

[0078] 2) The thickness of the electrolyte layer 362 is 0.1 μm to 50 μm;

[0079] 3) The thickness of the anode layer 361 is 0.1 mm to 4 cm;

[0080] 4) The thicknesses of the first anode current collector 311, the second anode current collector 313, the first cathode current collector 331, and the second cathode current collector 333 are each independently 0.5 mm to 1 cm;

[0081] 5) The thickness of the first insulating layer 312 and the second insulating layer 332 are each independently 0.5 mm to 1 cm.

[0082] More preferably, one or more of the following conditions are met:

[0083] 1) The thickness of the cathode layer 363 is 10μm to 30μm;

[0084] 2) The thickness of the electrolyte layer 362 is 5μm to 20μm;

[0085] 3) The thickness of the anode layer 361 is 0.5mm to 3cm;

[0086] 4) The thicknesses of the first anode current collector 311, the second anode current collector 313, the first cathode current collector 331, and the second cathode current collector 333 are each independently 0.8 mm to 1 cm;

[0087] 5) The thickness of the first insulating layer 312 and the second insulating layer 332 are each independently 0.8 mm to 1 cm.

[0088] In some implementations, one or more of the following conditions are met:

[0089] 1) The depth of channel 364 is 0.01mm to 4.99cm;

[0090] 2) The radial cross-sectional shape of flow channel 364 is semi-circular, semi-elliptical or polygonal.

[0091] By controlling the depth of the flow channel 364 to 0.01 mm to 4.99 cm, the structural strength of the anode layer 361 is not reduced while increasing the flow area of ​​fuel gas.

[0092] Preferably, the depth of the flow channel 364 is 0.1 mm to 3.99 cm.

[0093] Preferably, the radial cross-sectional shape of the flow channel 364 is semi-circular.

[0094] The radial cross-sectional shape of flow channel 364 is semi-circular, which can better disperse the thermal and mechanical stress generated during SOFC operation.

[0095] In some implementations, one or more of the following conditions are met:

[0096] 1) The raw materials for cathode layer 363 include ABO3 type perovskite material and pore-forming agent;

[0097] 2) The raw materials for electrolyte layer 362 include zirconia-based ceramic materials;

[0098] 3) The raw materials for the anode layer 361 include metal-ceramic composite materials and pore-forming agents;

[0099] 4) The raw materials of the first anode current collector 311, the second anode current collector 313, the first cathode current collector 331 and the second cathode current collector 333 include one or more of iron, copper, chromium and nickel;

[0100] 5) The raw materials for the first insulating layer 312 and the second insulating layer 332 include one or more of alumina, mica, asbestos, marble, and glass.

[0101] Preferably, in the ABO3 type perovskite material, A is lanthanum (La) and / or strontium (Sr), and B is one or more of manganese (Mn), iron (Fe) and cobalt (Co).

[0102] More preferably, ABO3 type perovskite materials include lanthanum strontium manganese oxide (La). x Sr 1-x MnO3, LSM) and / or lanthanum strontium iron cobalt oxide (La) x Sr 1-x Fe y Co 1-y O3,LSFC), where 0≤x≤1, 0≤y≤1.

[0103] Among them, La x Sr 1-x MnO3 is suitable for high-temperature SOFCs, but suffers from drawbacks in medium- and low-temperature SOFCs, including insufficient electrochemical activity, excessively high electrical resistance, and lack of ionic conductivity. (The text abruptly shifts to a seemingly unrelated topic about La.) x Sr 1-x Compared to MnO3, La x Sr 1-x Fe y Co 1-y O3 has higher mixed conductivity (electron-ion mixed conductor) and electrochemical activity, which can effectively improve the electrochemical performance of the SOFC.

[0104] In some specific embodiments, the raw material for the cathode layer 363 is La. x Sr 1-x Fe y Co 1-y O3.

[0105] Preferably, the zirconia-based ceramic material includes one or more of yttrium oxide-stabilized zirconia (YSZ), scandium oxide-stabilized zirconia (ScSZ), and yttrium oxide and scandium oxide co-stabilized zirconia (ScYSZ).

[0106] More preferably, the electrolyte layer 362 is made of yttrium-stabilized zirconium oxide (YSZ).

[0107] In some specific embodiments, the yttrium content in YSZ is 8 mol%.

[0108] Preferably, the metal-ceramic composite material includes a metal material and a zirconia-based ceramic material; wherein the metal material includes a metallic element and / or a metal oxide, the metallic element may be nickel (Ni) and / or copper (Cu), and the metal oxide may be nickel oxide (NiO) and / or copper oxide (CuO); the zirconia-based ceramic material includes one or more of YSZ, ScSZ, and ScYSZ.

[0109] More preferably, the metal-ceramic composite material includes metal oxide and zirconia-based ceramic materials.

[0110] In some specific implementations, the metal-ceramic composite material is NiO-YSZ.

[0111] Preferably, the raw materials of the first anode current collector 311, the second anode current collector 313, the first cathode current collector 331, and the second cathode current collector 333 are each independently one or more of iron (Fe)-based alloys, nickel (Ni)-based alloys, and chromium (Cr)-based alloys.

[0112] More preferably, the raw materials of the first anode current collector 311, the second anode current collector 313, the first cathode current collector 331, and the second cathode current collector 333 are each independently ferritic stainless steel.

[0113] Preferably, the raw materials for the first insulating layer 312 and the second insulating layer 332 are each independently mica and / or glass.

[0114] In some embodiments, the pore-forming agent includes one or more of graphite, starch, and polymethyl methacrylate.

[0115] The anode layer 361 and cathode layer 363 require a sufficiently large specific surface area to provide ample space for chemical and electrochemical reactions, and to allow oxidizing gases and fuel gases to diffuse freely within them. Therefore, pore-forming agents are typically added to the raw materials of the anode layer 361 and cathode layer 363. Materials such as graphite, starch, and polymethyl methacrylate (PMMA) are used as pore-forming agents, which can oxidize during sintering to generate carbon dioxide and water vapor, thereby forming a porous structure in the anode layer 361 and cathode layer 363.

[0116] Preferably, the pore-forming agent is polymethyl methacrylate (PMMA).

[0117] Preferably, in the raw materials of the anode layer 361, the mass ratio of metal oxide, zirconia-based ceramic material and pore-forming agent is (40-60):(30-40):(15-25).

[0118] Preferably, in the raw materials of the cathode layer 363, the mass ratio of ABO3 type perovskite material to pore-forming agent is 100:10.

[0119] In some embodiments, the raw materials for the anode layer 361, the electrolyte layer 362, and the cathode layer 363 each independently include one or more of a solvent, a dispersant, a binder, and a plasticizer.

[0120] Preferably, the solvent includes at least one selected from water, ethanol, xylene, n-butanol, and isopropanol;

[0121] Preferably, the dispersant includes at least one of terpineol, fish oil, and triethanolamine;

[0122] Preferably, the binder includes at least one of polyvinyl alcohol, polyvinyl butyral, ethyl cellulose, and acrylic emulsion;

[0123] Preferably, the plasticizer includes polyethylene glycol 400 and / or dibutyl phthalate.

[0124] In some embodiments, the symmetrical solid oxide fuel cell further includes a first transmission surface 351 that electrically connects the first anode current collector 311 and the first cathode current collector 331, and a second transmission surface 352 that electrically connects the second anode current collector 313 and the second cathode current collector 333.

[0125] Electrons released from the anode layer 361 of the first single cell 320 are sequentially transported to the cathode layer 363 of the second single cell 340 via the second anode current collector 313, the second transmission surface 352, and the second cathode current collector 333. Meanwhile, the first anode current collector 311 can collect electrons released from the anode layers 361 of other single cells and transport them to the cathode layer 363 of the first single cell 320 via the first transmission surface 351 and the first cathode current collector 331.

[0126] Preferably, the first transmission surface 351 and the second transmission surface 352 are located on both sides of the first single cell and are perpendicular to the thickness direction.

[0127] In some implementations, one or more of the following conditions are met:

[0128] 1) The thickness of the first transmission surface 351 and the second transmission surface 352 are each independently 0.1 mm to 1 cm;

[0129] 2) The radial cross-sectional shapes of the first transmission surface 351 and the second transmission surface 352 are each independently circular arcs.

[0130] 3) The raw materials of the first transmission surface 351 and the second transmission surface 352 include one or more of iron, copper, chromium and nickel.

[0131] Preferably, the thickness of the second transmission surface 351 and the second transmission surface 352 are each independently 0.5 mm to 1 cm.

[0132] More preferably, the thickness of the first transmission surface 351 and the second transmission surface 352 are each independently 0.8 mm to 1 cm.

[0133] Preferably, the raw materials for the first transmission surface 351 and the second transmission surface 352 are each independently one or more of iron (Fe)-based alloys, nickel (Ni)-based alloys, and chromium (Cr)-based alloys.

[0134] More preferably, the raw materials of the first transmission surface 351 and the second transmission surface 352 are each independently ferritic stainless steel.

[0135] In some embodiments, the symmetrical solid oxide fuel cell further includes a sealing layer (not shown) disposed on the surface of the anode layer 361 not covered by the electrolyte layer 362 and the second anode current collector 313.

[0136] The sealing layer and electrolyte layer 362 can isolate oxidizing gases and fuel, confining them to their respective spaces and preventing them from penetrating each other, thereby improving the thermal cycling performance of SOFC.

[0137] Preferably, the raw material of the sealing layer includes at least one of zirconia-based ceramic materials, glass, and mica.

[0138] More preferably, the sealing layer is made of zirconia-based ceramic material.

[0139] The raw material of the sealing layer is the same as that of the electrolyte layer 362. Therefore, during preparation, a layer of zirconia-based ceramic material can be directly coated on the surface of the anode layer 361 that is not covered by the second anode current collector layer 313. On the one hand, it serves as the electrolyte layer 362 to transport oxygen negative ions, and on the other hand, it can serve as a sealing layer to isolate oxidizing gas and fuel, thereby reducing processing difficulty and preparation cost.

[0140] In a second aspect, the present invention provides a method for preparing a symmetrical solid oxide fuel cell, comprising the following steps:

[0141] An anode layer 361 is formed with spaced-out flow channels 364 on its surface for the flow of fuel gas.

[0142] An electrolyte layer 362 is formed on the surface of the anode layer 361 away from the flow channel 364;

[0143] A cathode layer 363 is formed on the electrolyte layer 362 to obtain a first single cell 320 and a second single cell 340.

[0144] The first anode current collector 311 and the first cathode current collector 331 are electrically connected, and the second anode current collector 313 and the second cathode current collector 333 are electrically connected.

[0145] A symmetrical solid oxide fuel cell is obtained by stacking the first anode current collector 311, the first insulating layer 312, the second anode current collector 313, the first single cell 320, the first cathode current collector 331, the second insulating layer 332, and the second cathode current collector 333 in sequence, with the anode layer 361 of the first single cell 320 facing the second anode current collector 313 and the cathode layer 363 of the second single cell 340 facing the second cathode current collector 333.

[0146] Please see Figure 5The flowchart illustrates a method for preparing a symmetric SOFC in one embodiment, comprising the following steps:

[0147] S1: Prepare a first mixture containing a metal-ceramic composite material and a pore-forming agent, a second mixture containing a zirconia-based ceramic material, and a third mixture containing an ABO3-type perovskite material and a pore-forming agent.

[0148] Preferably, the metal oxide, zirconia-based ceramic material, pore-forming agent, solvent, dispersant, binder, and plasticizer are mixed evenly through a mixing process such as roller milling, ball milling, or stirring to obtain a first mixture.

[0149] Preferably, the zirconia-based ceramic material and the pore-forming agent, as well as at least one of the solvent, dispersant, binder and plasticizer, are mixed evenly by a mixing process such as roller milling, ball milling or stirring to obtain a second mixture.

[0150] Preferably, the ABO3 type perovskite material and the pore-forming agent, as well as at least one of the solvent, dispersant, binder and plasticizer, are mixed evenly by a mixing process such as roller milling, ball milling or stirring to obtain a third mixture.

[0151] S2: The first mixture is pressed into shape and subjected to the first calcination to obtain an anode layer 361 with spaced flow channels 364 for fuel gas to flow through on its surface.

[0152] Preferably, the method for pressing the first mixture is dry pressing or cold isostatic pressing.

[0153] Dry pressing involves placing the first mixture in a mold, causing the powder particles to come close together and bond firmly through friction under external force to form a green body of a certain shape. It has advantages such as high production efficiency, low labor requirements, low scrap rate, and short production cycle, making it suitable for mass industrial production. Isostatic pressing, a special method developed based on dry pressing, applies pressure uniformly from all directions to the first mixture in an elastic mold, thereby obtaining a uniform, dense green body with minimal firing shrinkage. However, it suffers from drawbacks such as complex and expensive equipment and low production efficiency.

[0154] Preferably, the first calcination condition is calcination at 1000℃ for 200 min to 400 min.

[0155] Understandably, the room temperature range is 20℃ to 30℃.

[0156] S3: The second mixture is applied to the surface of the anode layer 361 away from the flow channel 364 and subjected to a second calcination to obtain the electrolyte layer 362.

[0157] Preferably, the method of covering the second mixture on the surface of the anode layer 361 away from the flow channel 364 is one or more of screen printing, casting, thermal spraying, spin coating and scraping.

[0158] More preferably, the method of covering the second mixture on the surface of the anode layer 361 away from the flow channel 364 is screen printing.

[0159] The thickness of the electrolyte layer 362 is ≤100μm. The thickness of the film can be controlled more accurately by using a high-precision screen printing method, so as to obtain an electrolyte layer 362 with uniform thickness and low internal resistance.

[0160] Preferably, the second calcination conditions are calcination at 1000°C for 200-300 minutes and calcination at 1400°C for 300-600 minutes.

[0161] More preferably, the second calcination conditions are calcination at 600°C for 200-300 min, then calcination at 1000°C for 200-300 min, and finally calcination at 1400°C for 300-600 min.

[0162] Preferably, the second mixture is simultaneously applied to the surface of the anode layer 361 away from the flow channel 364 and to the two sides of the anode layer 361 near the flow channel 364, and then subjected to a second calcination to obtain the electrolyte layer 362.

[0163] The electrolyte layer 362 covers the three surfaces of the anode layer 361, enabling the electrolyte layer 362 to play a sealing and isolation role, eliminating the need for the preparation of a sealing layer, which helps to reduce processing difficulty and preparation cost.

[0164] Optionally, when the electrolyte layer 362 only covers the surface of the anode layer 361 away from the flow channel 364, the method further includes the following step: forming a sealing layer on two sides of the anode layer 361 near the flow channel 364. The sealing layer is made of glass and / or mica, and is prepared by one or more of the following methods: screen printing, casting, thermal spraying, spin coating, and blade coating.

[0165] S4: The third mixture is applied to the electrolyte layer 362 and then calcined for the third time to obtain the cathode layer 363, thereby obtaining the first single cell 320 and the second single cell 340.

[0166] Preferably, the method of covering the third mixture onto the electrolyte layer 362 is one or more of the following: screen printing, casting, thermal spraying, spin coating, and scraping.

[0167] More preferably, the method for coating the third mixture onto the electrolyte layer 362 is screen printing.

[0168] The thickness of the cathode layer 363 is ≤100μm. The thickness of the film can be controlled more accurately by using a high-precision screen printing method, so as to obtain a cathode layer 363 with uniform thickness and low internal resistance.

[0169] Preferably, the third calcination condition is calcination at 1000℃ for 200 min to 300 min.

[0170] S5: Make the first anode current collector 311 and the first cathode current collector 331 electrically connected, and make the second anode current collector 313 and the second cathode current collector 333 electrically connected.

[0171] In some embodiments, forming an electrical connection between the first anode current collector 311 and the first cathode current collector 331, and forming an electrical connection between the second anode current collector 313 and the second cathode current collector 333, includes the following steps;

[0172] The first anode current collector layer 311 and the first cathode current collector layer 331 are electrically connected through the first transmission surface 351;

[0173] The second anode current collector 313 and the second cathode current collector 333 are electrically connected through the second transmission surface 352.

[0174] Preferably, the process of forming an electrical connection between the first anode current collector 311 and the first cathode current collector 331 through the first transmission surface 351 includes the following steps: forming a first metal plate, the first metal plate including a first transmission surface 351 with a radial cross section in the shape of an arc, and a first anode current collector 311 and a first cathode current collector 331 that are parallel to each other and connected to the first transmission surface 351.

[0175] Preferably, the process of forming an electrical connection between the second anode current collector 313 and the second cathode current collector 333 through the second transmission surface 352 includes the following steps: forming a second metal plate, the second metal plate including a second transmission surface 352 with a radial cross section in the shape of an arc, and a second anode current collector 313 and a second cathode current collector 333 that are parallel to each other and connected to the second transmission surface 352.

[0176] More preferably, the methods for forming the first metal plate and the method for forming the second metal plate are each independently one of the following: 1) a cutting, shearing and bending process; 2) a powder metallurgy process.

[0177] S6: The first anode current collector 311, the first insulating layer 312, the second anode current collector 313, the first single cell 320, the first cathode current collector 331, the second insulating layer 332, and the second cathode current collector 333 are stacked sequentially, and the anode layer 361 of the first single cell 320 faces the second anode current collector 313 and the cathode layer 363 of the second single cell 340 faces the second cathode current collector 333, to obtain a symmetrical solid oxide fuel cell.

[0178] In a third aspect, the present invention provides a battery stack comprising a plurality of symmetrical solid oxide fuel cells as described above, arranged in a stacked manner.

[0179] Please see Figure 6 This is a three-dimensional structural diagram of a battery stack in one embodiment, which consists of multiple such... Figure 3 The symmetrical SOFCs shown are stacked together, with the first anode current collector 311 of the symmetrical SOFC facing the second single cell 340 of the adjacent symmetrical SOFC.

[0180] The present invention will be further described in detail below with reference to specific embodiments.

[0181] Example 1

[0182] (1) NiO, YSZ, PMMA, water, and polyvinyl alcohol were roller-milled and mixed in a mass ratio of 40:40:10:8:2, and then dried to obtain a first mixture; YSZ, ethanol, and polyvinyl butyral were ball-milled and mixed in a mass ratio of 20:79:1 to obtain a second mixture; La x Sr 1-x Fe y Co 1-y O3, starch, water, and polyvinyl alcohol were mixed by roller milling in a mass ratio of 80:10:8:2 and then dried to obtain a third mixture.

[0183] (2) The first mixture is dry-pressed to form a first blank; the first blank is placed in a box furnace and heated from room temperature to 1000°C for 200 min, calcined for 360 min, and then cooled from 1000°C to room temperature for 200 min to obtain an anode layer 361 with spaced flow channels 364 on its surface.

[0184] The dimensions (L×W×H) of the anode layer 361 are 60mm×140mm×3mm; the radial cross-sectional shape of the flow channel 364 is semi-circular, and its depth (or radius) is 1mm.

[0185] (3) The second mixture is applied to the surface of the anode layer 361 away from the flow channel 364 and the two sides of the anode layer 361 close to the flow channel 364 by screen printing to obtain the second blank; the second blank is placed in a box furnace and heated from room temperature to 1000°C for 200 min, calcined for 300 min, heated from 1000°C to 1400°C for 200 min, calcined for 360 min, and then cooled from 1400°C to room temperature for 400 min to obtain the electrolyte layer 362 covering the three surfaces of the anode layer 361.

[0186] The electrolyte layer 362 has dimensions (L×W×H) of 60mm×140mm×10μm, which does not include the electrolyte layer 362 on the two sides of the anode layer 361.

[0187] (4) The third mixture is covered on the electrolyte layer 362 by screen printing to obtain the third blank; the third blank is placed in a box furnace and heated from room temperature to 1000°C for 300 minutes, calcined for 300 minutes, and then cooled from 1000°C to room temperature for 300 minutes to obtain the cathode layer 363, thereby obtaining the first single cell 320 and the second single cell 340.

[0188] The dimensions (L×W×H) of the cathode layer 363 are 50mm×130mm×20μm.

[0189] (5) A first metal plate is formed by cutting, trimming and bending processes. The first metal plate includes a first transmission surface 351 with a radial cross-section in the shape of an arc, and a first anode current collector layer 311 and a first cathode current collector layer 331 that are parallel to each other and connected to the ends of the first transmission surface 351. A second metal plate is formed by cutting, trimming and bending processes. The second metal plate includes a second transmission surface 352 with a radial cross-section in the shape of an arc, and a second anode current collector layer 313 and a second cathode current collector layer 333 that are parallel to each other and connected to the ends of the second transmission surface 352.

[0190] The dimensions (L×W×H) of the first anode current collector 311, the second anode current collector 313, the first cathode current collector 331, and the second cathode current collector 333 are all 60mm×140mm×1mm; the thickness of the first transmission surface 351 and the second transmission surface 352 is 1mm.

[0191] (6) The first anode current collector 311, the first insulating layer 312, the second anode current collector 313, the first single cell 320, the first cathode current collector 331, the second insulating layer 332, and the second cathode current collector 333 are stacked in sequence, and the anode layer 361 of the first single cell 320 faces the second anode current collector 313 and the cathode layer 363 of the second single cell 340 faces the second cathode current collector 333, to obtain a symmetrical solid oxide fuel cell.

[0192] (7) Multiple symmetrical solid oxide fuel cells are stacked to form a battery stack.

[0193] Example 2

[0194] (1) NiO, YSZ, PMMA, water, and polyvinyl alcohol were roller-milled and mixed in a mass ratio of 40:35:13:10:2, and then dried to obtain a first mixture; YSZ, ethanol, and polyvinyl butyral were ball-milled and mixed in a mass ratio of 25:74:1 to obtain a second mixture; La x Sr 1-x Fe y Co 1-y O3, triethanolamine, polyvinyl alcohol and starch were mixed by roller milling in a mass ratio of 100:100:5:10 and then dried to obtain the third mixture.

[0195] (2) The first mixture is dry-pressed to form a first blank; the first blank is placed in a box furnace and heated from room temperature to 1000°C for 300 min, calcined for 240 min, and then cooled from 1000°C to room temperature for 300 min to obtain an anode layer 361 with spaced flow channels 364 on its surface.

[0196] The dimensions (L×W×H) of the anode layer 361 are 130mm×250mm×5mm; the radial cross-sectional shape of the flow channel 364 is semi-circular, and its depth (or radius) is 2mm.

[0197] (3) The second mixture is applied to the surface of the anode layer 361 away from the flow channel 364 and the two sides of the anode layer 361 close to the flow channel 364 by screen printing to obtain the second blank; the second blank is placed in a box furnace and heated from room temperature to 600°C for 300 minutes, calcined for 300 minutes, then heated from 600°C to 1000°C for 200 minutes, calcined for 300 minutes, then heated from 1000°C to 1400°C for 200 minutes, calcined for 300 minutes, and finally cooled from 1400°C to room temperature for 600 minutes to obtain the electrolyte layer 362 covering the three surfaces of the anode layer 361.

[0198] The electrolyte layer 362 has dimensions (L×W×H) of 110mm×230mm×20μm, which does not include the electrolyte layer 362 on the two sides of the anode layer 361.

[0199] (4) The third mixture is covered on the electrolyte layer 362 by screen printing to obtain the third blank; the third blank is placed in a box furnace and heated from room temperature to 1000°C for 400 min, calcined for 300 min, and then cooled from 1000°C to room temperature for 300 min to obtain the cathode layer 363, thereby obtaining the first single cell 320 and the second single cell 340.

[0200] The dimensions (L×W×H) of the cathode layer 363 are 90mm×210mm×30μm.

[0201] (5) A first metal plate is formed by powder metallurgy process. The first metal plate includes a first transmission surface 351 with a radial cross section of arc shape, and a first anode current collector layer 311 and a first cathode current collector layer 331 that are parallel to each other and connected to the ends of the first transmission surface 351. A second metal plate is formed by powder metallurgy process. The second metal plate includes a second transmission surface 352 with a radial cross section of arc shape, and a second anode current collector layer 313 and a second cathode current collector layer 333 that are parallel to each other and connected to the ends of the second transmission surface 352.

[0202] The dimensions (L×W×H) of the first anode current collector 311, the second anode current collector 313, the first cathode current collector 331, and the second cathode current collector 333 are all 130mm×250mm×5mm; the thickness of the first transmission surface 351 and the second transmission surface 352 is 5mm.

[0203] (6) The first anode current collector 311, the first insulating layer 312, the second anode current collector 313, the first single cell 320, the first cathode current collector 331, the second insulating layer 332, and the second cathode current collector 333 are stacked in sequence, and the anode layer 361 of the first single cell 320 faces the second anode current collector 313 and the cathode layer 363 of the second single cell 340 faces the second cathode current collector 333, to obtain a symmetrical solid oxide fuel cell.

[0204] (7) Multiple symmetrical solid oxide fuel cells are stacked to form a battery stack.

[0205] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0206] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A symmetrical solid oxide fuel cell, characterized in that, It includes a first anode current collector layer, a first insulating layer, a second anode current collector layer, a first single cell, a first cathode current collector layer, a second insulating layer, a second cathode current collector layer, and a second single cell, which are stacked in sequence. The first single cell and the second single cell each independently include an anode layer, an electrolyte layer and a cathode layer stacked sequentially; the surface of the anode layer away from the electrolyte layer is provided with spaced-apart flow channels for the flow of fuel gas; the anode layer of the first single cell faces the second anode current collector layer, and the cathode layer of the second single cell faces the second cathode current collector layer. The first anode current collector is electrically connected to the first cathode current collector, and the second anode current collector is electrically connected to the second cathode current collector, so as to connect the first single cell and the second single cell in series.

2. The symmetrical solid oxide fuel cell as described in claim 1, characterized in that, One or more of the following conditions must be met: 1) The thickness of the cathode layer is 1 μm to 100 μm; 2) The thickness of the electrolyte layer is 0.1 μm to 100 μm; 3) The thickness of the anode layer is 0.01 mm to 5 cm; 4) The thicknesses of the first anode current collector, the second anode current collector, the first cathode current collector, and the second cathode current collector are each independently 0.1 mm to 1 cm; 5) The thickness of the first insulating layer and the second insulating layer are each independently 0.1 mm to 1 cm.

3. The symmetrical solid oxide fuel cell as described in claim 2, characterized in that, One or more of the following conditions must be met: 1) The depth of the flow channel is 0.01 mm to 4.99 cm; 2) The radial cross-sectional shape of the flow channel is semi-circular, semi-elliptical, or polygonal.

4. The symmetrical solid oxide fuel cell as described in claim 1, characterized in that, One or more of the following conditions must be met: 1) The raw materials for the cathode layer include ABO3 type perovskite material and a pore-forming agent; 2) The raw material for the electrolyte layer includes zirconia-based ceramic materials; 3) The raw materials for the anode layer include metal-ceramic composite materials and pore-forming agents; 4) The raw materials of the first anode current collector, the second anode current collector, the first cathode current collector, and the second cathode current collector each independently include one or more of iron, copper, chromium, and nickel; 5) The raw materials of the first insulating layer and the second insulating layer each independently include one or more of alumina, mica, asbestos, marble, and glass.

5. The symmetrical solid oxide fuel cell according to any one of claims 1 to 4, characterized in that, The symmetrical solid oxide fuel cell further includes a first transmission surface that electrically connects the first anode current collector and the first cathode current collector, and a second transmission surface that electrically connects the second anode current collector and the second cathode current collector.

6. The symmetrical solid oxide fuel cell as described in claim 5, characterized in that, One or more of the following conditions must be met: 1) The thickness of the first transmission surface and the second transmission surface are each independently 0.1 mm to 1 cm; 2) The radial cross-sectional shapes of the first transmission surface and the second transmission surface are each independently circular arcs; 3) The raw materials of the first transmission surface and the second transmission surface each independently include one or more of iron, copper, chromium and nickel.

7. A method for preparing a symmetrical solid oxide fuel cell, characterized in that, Includes the following steps: An anode layer is formed with spaced channels on its surface for the flow of fuel gas. An electrolyte layer is formed on the surface of the anode layer away from the flow channel; A cathode layer is formed on the electrolyte layer to obtain a first single cell and a second single cell. The first anode current collector and the first cathode current collector are electrically connected, and the second anode current collector and the second cathode current collector are electrically connected. The first anode current collector, the first insulating layer, the second anode current collector, the first single cell, the first cathode current collector, the second insulating layer, and the second cathode current collector are stacked sequentially, with the anode surface of the first single cell facing the second anode current collector and the cathode surface of the second single cell facing the second cathode current collector, to obtain the symmetrical solid oxide fuel cell.

8. The method for preparing a symmetrical solid oxide fuel cell as described in claim 7, characterized in that, The process of forming an electrical connection between the first anode current collector and the first cathode current collector, and forming an electrical connection between the second anode current collector and the second cathode current collector includes the following steps: The first anode current collector and the first cathode current collector are electrically connected through the first transmission surface; The second anode current collector and the second cathode current collector are electrically connected through the second transmission surface.

9. The method for preparing a symmetrical solid oxide fuel cell as described in claim 8, characterized in that, It also includes the following steps: Prepare a first mixture containing a metal ceramic material and a pore-forming agent, a second mixture containing a zirconia-based ceramic material, and a third mixture containing an ABO3-type perovskite material and a pore-forming agent; The first mixture is pressed into shape and subjected to a first calcination to obtain the anode layer; The second mixture is applied to the surface of the anode layer away from the flow channel, and then subjected to a second calcination to obtain the electrolyte layer. The third mixture is applied over the electrolyte layer and then subjected to a third calcination to obtain the cathode layer.

10. A battery stack, characterized in that, The symmetrical solid oxide fuel cell as described in any one of claims 1 to 6 includes multiple stacked layers.

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