Thermal-electric-chemical coupled solid oxide electric pile

Abstract

The invention discloses a thermal-electric-chemical coupled solid oxide stack which comprises a lower end plate and an upper end plate, and a plurality of SOFC (solid oxide fuel cell) single cells and SOEC (solid oxide electric cell) single cells are arranged between the lower end plate and the upper end plate; each SOFC single battery comprises an SOFC cathode, an SOFC electrolyte and an SOFC anode which are crimped in sequence; each SOEC single battery comprises an SOEC cathode, an SOEC electrolyte and an SOEC anode which are crimped in sequence; the chamber where the SOEC anode is located is communicated with the chamber where the SOFC cathode is located, and oxygen generated by electrolysis of the SOEC anode can enter the SOFC cathode side to participate in the reaction; and the SOFC single batteries and the SOEC single batteries are electrically connected in series through connectors or current collectors. According to the invention, the SOFC units and the SOEC units are arranged in the same electric pile alternately or in blocks, and specific gas paths and circuits are opened, so that gradient utilization of energy and efficient and stable operation of the system are realized.

Description

A thermo-electric-chemical coupled solid oxide fuel cell stack Technical Field

[0001] This invention pertains to hydrogen energy and high-temperature electrochemical devices, specifically a thermo-electro-chemical coupled solid oxide fuel cell stack. Background Technology

[0002] Hydrogen energy, as an important carrier of clean energy, has attracted much attention regarding its production technology. Solid oxide electrolyzers (SOECs) utilize high-temperature steam electrolysis to produce hydrogen, offering advantages such as high electrolysis efficiency and the elimination of the need for precious metal catalysts. However, the commercialization of SOEC technology still faces the following key challenges:

[0003] Endothermic reaction and challenges in thermal management: Steam electrolysis reaction of SOEC (H₂O + 2e⁻) - → H2+ O 2- Below the thermal neutral voltage, the process is strongly endothermic. In order to maintain the operation of the stack at a high temperature of 700-850℃, it is usually necessary to heat the intake gas or operate at a high overpotential (leading to a decrease in electrical efficiency). This makes it easy to generate a huge temperature gradient inside the stack, triggering thermal stress, which can lead to cell delamination or sealing failure.

[0004] High power consumption costs: The main cost of hydrogen production through water electrolysis lies in power consumption. Although SOEC is more efficient than cryogenic electrolysis technology, reducing DC power consumption per cubic meter of hydrogen remains a core requirement for large-scale applications.

[0005] Carbon buildup issues with hydrocarbon fuel-assisted SOEC: To reduce power consumption, some studies have proposed using hydrocarbon fuels (such as methane) to assist SOEC. However, in conventional SOFC / SOEC, direct introduction of methane into the anode easily leads to cracking and carbon buildup, resulting in catalyst deactivation. SOFC stands for Solid Oxide Fuel Cell.

[0006] Furthermore, in conventional SOFC operation, a large amount of air needs to be introduced into the cathode as an oxidant. Since the oxygen concentration in air is only 21% and contains a large amount of nitrogen (approximately 79%) that does not participate in the reaction, this not only limits the Nernst potential of the battery and reduces power generation efficiency, but also requires an excessive amount of air (excess air coefficient > 4) to maintain thermal balance, resulting in significant parasitic power consumption from the blower. Simultaneously, heating a large amount of cold air to an operating temperature of approximately 800°C consumes a significant amount of thermal energy, further reducing the overall system efficiency.

[0007] In existing technologies, SOFC (power generation / heat release) and SOEC (electrolysis / heat absorption) stacks are typically treated as two independent modules, coupled at the system level through an external heat exchanger. This approach suffers from problems such as large pipeline heat loss, large system size, and delayed thermal response, and cannot solve the thermal shock and energy efficiency matching problems at the microscopic level of a single cell. Summary of the Invention

[0008] Purpose of the invention: In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a solid oxide fuel cell stack with high electrochemical efficiency and self-generated voltage compensation for thermo-electro-chemical coupling.

[0009] Technical Solution: The present invention discloses a thermo-electro-chemically coupled solid oxide fuel cell stack, comprising a lower end plate and an upper end plate, wherein a plurality of SOFC individual cells and SOEC individual cells are disposed between the lower end plate and the upper end plate; the SOFC individual cell comprises an SOFC cathode, an SOFC electrolyte, and an SOFC anode sequentially pressed together; the SOEC individual cell comprises an SOEC cathode, an SOEC electrolyte, and an SOEC anode sequentially pressed together; the chamber containing the SOEC anode is connected to the chamber containing the SOFC cathode, and oxygen generated by the electrolysis of the SOEC anode can enter the SOFC cathode side to participate in the reaction; the SOFC individual cells and the SOEC individual cells are electrically connected in series through connectors or current collectors.

[0010] Furthermore, several hybrid repeating units are arranged between the lower end plate and the upper end plate; the hybrid repeating unit includes an alternately coupled SOFC anode seal, an alternately coupled SOFC anode current collector, a first alternately coupled battery frame for fixing SOFC single cells, a coupling chamber seal, a coupling chamber current collector, a second alternately coupled battery frame for fixing SOEC single cells, an alternately coupled SOEC cathode seal, and an alternately coupled SOEC cathode current collector. The alternately coupled SOFC anode seal and the SOFC alternately coupled anode current collector are arranged on the connector or the lower end plate, the coupling chamber seal and the coupling chamber current collector are arranged between the SOFC single cells and the SOEC single cells, and the SOEC cathode seal and the SOEC cathode current collector are arranged on the second alternately coupled battery frame.

[0011] The oxygen generated by the SOEC cell in electrolysis mode is directly transported to the SOFC cathode surface of the SOFC cell, serving as an oxidant for the SOFC power generation reaction.

[0012] Furthermore, an oxygen exchange chamber is formed between the first alternating coupled battery frame, the SOFC single cell, the coupling chamber seal, the SOEC single cell, and the second alternating coupled battery frame. The coupling chamber current collector is placed inside the oxygen exchange chamber, and the oxygen generated by the SOEC anode can be transferred to the SOFC cathode through the oxygen exchange chamber.

[0013] Furthermore, the SOFC anode is disposed on the side of the first alternating coupled battery frame near the alternating coupled SOFC anode current collector, and the SOFC cathode is disposed on the side of the first alternating coupled battery frame near the coupling chamber current collector.

[0014] Furthermore, the SOEC anode is disposed on the side of the second alternating coupled battery frame near the coupling chamber current collector, and the SOEC cathode is disposed on the side of the second alternating coupled battery frame near the SOEC cathode current collector.

[0015] Furthermore, several SOFC repeating units and SOEC repeating units are provided between the lower end plate and the upper end plate. The SOFC repeating units are separated from each other, from each other, and from each other by connectors.

[0016] Furthermore, the SOFC repeating unit includes a block-coupled SOFC anode seal, a block-coupled SOFC anode current collector, a first block-coupled battery frame for fixing the SOFC single cell, a block-coupled SOFC cathode seal, and a block-coupled SOFC cathode current collector. The block-coupled SOFC anode seal and the block-coupled SOFC anode current collector are disposed on the connector or the lower end plate, and the block-coupled SOFC cathode seal and the block-coupled SOFC cathode current collector are disposed on the side of the first block-coupled battery frame near the upper end plate.

[0017] Furthermore, the SOEC repeating unit includes a block-coupled SOEC anode seal, a block-coupled SOEC anode current collector, a second block-coupled battery frame for fixing SOEC individual cells, a block-coupled SOEC cathode seal, and a block-coupled SOEC cathode current collector. The block-coupled SOEC anode seal and the block-coupled SOEC anode current collector are disposed on the connector, and the block-coupled SOEC cathode seal and the block-coupled SOEC cathode current collector are disposed on the side of the second block-coupled battery frame near the upper end plate.

[0018] Furthermore, the block-coupled SOFC anode seal, the first block-coupled battery frame, the block-coupled SOFC cathode seal, the block-coupled SOEC anode seal, the second block-coupled battery frame, the block-coupled SOFC cathode seal, the lower end plate, the upper end plate, and the connector are all provided with through holes to form a vertical common gas channel, so that the chamber where the SOEC anode is located is connected to the chamber where the SOFC cathode is located.

[0019] Furthermore, the ratio of the number of SOFC repeating units to the number of SOEC repeating units is preset based on the target hydrogen production capacity, stack thermal balance calculations, and stress field simulation results.

[0020] Working principle:

[0021] 1. Steam Electrolysis and Oxygen Generation (SOEC Side): High-temperature steam is introduced into the SOEC cathode of the SOEC cell, where a reduction reaction occurs under the drive of an electric field to generate hydrogen and oxygen ions (H2O + 2e-).- →H2+ O 2- Oxygen ions pass through the SOEC electrolyte to the SOEC anode, where they lose electrons to generate high-purity oxygen (O₂). 2- →1 / 2 O2+2e - ).

[0022] 2. In-situ transport and reuse of oxygen (gas path coupling): This invention abandons the traditional practice of venting SOEC oxygen outside the reactor.

[0023] In the alternating coupling configuration of the single-cell anode, the pure oxygen generated by the SOEC anode directly enters the adjacent oxygen exchange chamber and rapidly diffuses to the opposite SOFC cathode surface within an extremely short microscopic distance.

[0024] In the block-coupled configuration, the pure oxygen generated in the electrolysis block is collected and then precisely guided to the SOFC cathode side of the power generation block through a common gas channel that runs through the stack.

[0025] 3. Oxygen-enriched power generation and internal compensation (SOFC side): Hydrocarbon fuels (such as methane, syngas, etc.) are introduced into the SOFC anode. Simultaneously, the SOFC cathode receives high-purity oxygen from the SOEC side as an oxidant, undergoing a reduction reaction (1 / 2 O₂ + 2e⁻). - →O 2- Oxygen ions pass through the SOFC electrolyte to the anode and react with the fuel to produce an oxidation reaction, releasing electrical energy and a large amount of heat.

[0026] 4. Deep coupling mechanism:

[0027] Mass and chemical coupling: The SOFC cathode directly utilizes pure oxygen generated by SOEC, eliminating the need for external air. This not only increases the local oxygen partial pressure from 0.21 atm to nearly 1 atm, significantly enhancing the Nernst potential of the SOFC, but also completely eliminates the parasitic power consumption of the air blower in traditional systems, as well as the huge heat loss caused by heating a large amount of inert nitrogen (air contains 79% nitrogen).

[0028] Electrical coupling: SOFC cells and SOEC cells are electrically connected in series via connectors. The high voltage generated by SOFC oxygen-enriched power generation directly offsets most of the voltage required for SOEC electrolysis within the stack. An external power source only needs to provide a minimal compensation voltage to maintain the overall hydrogen production process, significantly reducing the DC power consumption for hydrogen production.

[0029] Thermal coupling: The exothermic reaction (fuel oxidation) of SOFC and the endothermic reaction (steam electrolysis) of SOEC are closely integrated in physical space. The released heat is transferred directly to the endothermic side at the microscopic (between individual units) or macroscopic (between blocks) scale through the connector or internal airflow, realizing the thermal self-balance inside the stack and greatly reducing the temperature gradient and thermal stress.

[0030] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0031] 1. By alternating or dividing SOFC and SOEC units within the same fuel cell stack and connecting specific gas and electrical paths, energy cascade utilization and efficient and stable system operation are achieved. Thermal-electrical-chemical coupling is realized within the fuel cell stack, solving the thermal shock and energy efficiency matching problems at the single cell level from a microscopic scale.

[0032] 2. In-situ reuse of oxygen creates a unique internal gas circulation mechanism. The oxygen-rich gas generated by the SOEC anode electrolysis is directly guided to the SOFC cathode chamber through an internal micro-chamber or common flow channel. This design abandons the traditional SOFC practice of introducing a large amount of air. It uses the high-purity oxygen generated by SOEC as the oxidant of SOFC. This not only increases the oxygen partial pressure on the SOFC cathode side from 0.21 atm to nearly 1 atm, thereby significantly improving the open-circuit voltage and electrochemical efficiency of SOFC, but also eliminates the heat load required to heat a large amount of inert nitrogen gas, achieving system-level heat-mass balance.

[0033] 3. Self-generated voltage compensation: SOFC cells and SOEC cells are electrically connected in series inside the stack through connectors or current collectors. As an "embedded power source", the high voltage generated by SOFC (thanks to the oxygen-rich environment) is directly superimposed in series in the circuit, effectively offsetting most of the voltage required for SOEC electrolysis. This means that the external power source only needs to provide the remaining small voltage difference to drive the electrolysis reaction, thereby significantly reducing the external DC power consumption for hydrogen production.

[0034] 4. Excellent thermal management and structural flexibility: This invention provides two configurations: "alternating coupling of individual units" and "block coupling". Both configurations utilize the exothermic reaction of SOFC (fuel oxidation) to directly compensate for the endothermic reaction of SOEC (steam electrolysis). This compact thermal coupling design eliminates the bulky external heat exchanger of traditional systems, reduces the temperature gradient, and effectively reduces the risk of stack delamination or seal failure caused by thermal stress. Attached Figure Description

[0035] Figure 1 is a schematic diagram of the exploded structure of the hybrid repeating unit 6 in Embodiment 1 of the present invention;

[0036] Figure 2 is a structural schematic diagram of Embodiment 1 of the present invention;

[0037] Figure 3 is a structural schematic diagram of Embodiment 2 of the present invention;

[0038] Figure 4 is an exploded structural diagram of the SOFC repeating unit 7 in Embodiment 2 of the present invention;

[0039] Figure 5 is an exploded structural diagram of the SOEC repeating unit 8 in Embodiment 2 of the present invention. Detailed Implementation

[0040] Unless otherwise specified, all materials and reagents used in the following embodiments are commercially available. Experimental methods not specifically described in the embodiments are generally performed under standard conditions or as recommended by the manufacturer.

[0041] Example 1

[0042] As shown in Figure 1, the hybrid repeating unit 6 adopts a compact stacked design with "back-to-back" or "face-to-face" configurations, enabling short-distance in-situ reuse of oxygen. The stacked structure of the hybrid repeating unit 6, from bottom to top, consists of: an SOFC anode assembly, a first alternating coupled battery frame 603 for fixing the SOFC single cell 3, an intermediate oxygen coupling chamber, a second alternating coupled battery frame 606 for fixing the SOEC single cell 4, and an SOEC water vapor chamber. The SOFC anode assembly includes an alternating coupled SOFC anode seal 601 and an alternating coupled SOFC anode current collector 602, which are positioned close to the connector 5 for introducing fuel gas. The SOFC single cell 3 includes an SOFC cathode 301, an SOFC electrolyte 302, and an SOFC anode 303, which are sequentially pressed together. The SOFC anode 303 faces away from the connector 5; note its polarity: the SOFC anode 303 faces downwards, and the SOFC cathode 301 faces upwards. The intermediate oxygen coupling chamber is formed by the coupling chamber seal 604, the coupling chamber current collector 605, and the support structure on the SOEC anode 403 side, and is located between the SOFC cell 3 and the SOEC cell 4. The SOEC cell 4 includes an SOEC cathode 401, an SOEC electrolyte 402, and an SOEC anode 403 pressed together in sequence. The SOEC anode 403 faces the SOFC cell 3, and the SOEC cathode 401 faces away from the SOFC cell 3. Note their polarity: the SOEC anode 403 faces downwards, and the SOEC cathode 401 faces upwards, meaning that the SOEC anode 403 directly faces the SOFC cathode 301 below. The SOEC water vapor chamber is formed by the alternating coupling SOEC cathode seal 607 and is filled with the alternating coupling SOEC cathode current collector 608, through which high-temperature water vapor is introduced. The SOFC cathode 301 and the SOEC anode 403 achieve gas path connection and electrical series connection within the oxygen coupling assembly. The alternating coupling SOEC cathode current collector 608 is typically a porous metal mesh or a conductive ceramic slurry. The intermediate oxygen coupling chamber is closed (or only has a pressure regulating outlet) and is not directly vented to the outside air. Instead, it serves as a site for the generation and consumption of oxygen. The pure oxygen generated by the SOEC anode 403 directly enters the adjacent oxygen exchange chamber 609 and rapidly diffuses to the surface of the opposite SOFC cathode 301 within a very short microscopic distance.

[0043] As shown in Figure 2, the structure of the thermo-electro-chemical coupled solid oxide fuel cell (SOFC) is a single-cell alternating coupling structure. From bottom to top, it consists of a lower end plate 1, a hybrid repeating unit 6, a connector 5, another hybrid repeating unit 6, another connector 5, another hybrid repeating unit 6, and an upper end plate 2. The connector 5 serves as a base, isolating the fuel and water vapor of adjacent hybrid repeating units 6 and also conducting current. The SOFC fuel chamber is enclosed by alternating coupled SOFC anode seals 601, and is filled with alternating coupled SOFC anode current collectors 602. Hydrocarbon fuels (such as methane, biogas, etc.) are introduced here to supply the SOFC anode 303 above. The SOFC single cell 3 is fixed by the first alternating coupled cell frame 603. Note its polarity: the SOFC anode 303 faces downwards, and the SOFC cathode 301 faces upwards. The right side of the thermo-electro-chemical coupled SOFC has a fuel gas inlet 9 and a fuel gas outlet 12, while the left side has a water vapor inlet 10 and a hydrogen outlet 11.

[0044] The gas flow field is configured such that an oxygen exchange chamber is formed between the SOEC anode 403 of the SOEC cell 4 and the SOFC cathode 301 of the SOFC cell 3, or they are connected through a gas channel. The oxygen generated by the SOEC cell 4 in electrolysis mode is directly transported to the surface of the SOFC cathode 301 of the SOFC cell 3, serving as an oxidant for the SOFC power generation reaction.

[0045] In this embodiment, the first alternating coupled battery frame 603, the second alternating coupled battery frame 606, the connector 5, the lower end plate 1, and the upper end plate 2 are made of Crofer 22 stainless steel APU; the alternating coupled SOFC anode seal 601, the coupling chamber seal 604, and the alternating coupled SOEC cathode seal 607 are made of SiO2-B2O3-Na2O series glass; the alternating coupled SOFC anode current collector 602 and the alternating coupled SOEC cathode current collector 608 are made of nickel foam; the coupling chamber current collector 605 is made of Crofer 22 stainless steel APU mesh; and the SOFC cathode 301 and the SOEC anode 403 are made of perovskite La. 0.6 Sr 0.4 Co 0.8 Fe 0.2 O3; SOFC electrolyte 302 and SOEC electrolyte 402 are made of YSZ, and SOFC anode 303 and SOEC cathode 401 are made of Ni-YSZ cermet.

[0046] Working principle:

[0047] Step A, SOEC oxygen production:

[0048] An external power source (or a SOFC series power source) drives current to flow through the fuel cell stack. At the top SOEC cathode 401, water vapor undergoes a reduction reaction: H₂O + 2e⁻ - →H2+ O 2- Oxygen ions migrate downwards through the SOEC electrolyte 402 to the SOEC anode 403, where they lose electrons to generate pure oxygen.

[0049] Step B, Oxygen Transfer and Reuse:

[0050] The generated oxygen enters directly into the adjacent oxygen exchange chamber 609. Due to the extremely short distance (micrometer to millimeter scale), the oxygen rapidly diffuses to the surface of the SOFC cathode 301 below. Advantage: The oxygen concentration here is close to 100%, far exceeding the 21% concentration in air.

[0051] Step C, SOFC power generation:

[0052] At the SOFC cathode 301 below, a high concentration of oxygen undergoes a reduction reaction: O2 + 4e- - →2O 2- Oxygen ions pass through the SOFC electrolyte 302 to reach the SOFC anode 303, where they react with fuel (such as CH4) to generate electricity. Advantages: The high oxygen partial pressure significantly increases the Nernst potential of the SOFC, allowing it to output a higher voltage, thus more effectively offsetting the electrolysis voltage requirements of the SOEC.

[0053] Step D, Heat self-balance:

[0054] In SOFC, the power generation reaction (exothermic) occurs at the bottom, while in SOEC, the electrolysis reaction (endothermic) occurs at the top. The two are in close thermal contact through the coupling chamber current collector 605 in the middle, and the heat is directly conducted upwards without the need for a complex external heat exchange circuit.

[0055] This structure cleverly utilizes the "supply and demand relationship" between the SOEC anode 403 and the SOFC cathode 301 to construct an "oxygen micro-circulation" within the repeating unit. This not only solves the problem of heat loss from SOEC oxygen emissions but also significantly improves the power generation efficiency of SOFC through oxygen-enriched combustion (electrochemical combustion), making it an ideal architecture for achieving low-energy hydrogen production.

[0056] Example 2

[0057] As shown in Figure 3, the structure of the thermo-electro-chemical coupled solid oxide fuel cell stack is a block stack structure based on flow channel coupling, achieving oxygen reuse through the distribution of macroscopic flow channels. The solid oxide fuel cell stack is formed from bottom to top by a lower end plate 1, several alternately arranged SOFC repeating units 7 and SOEC repeating units 8, and an upper end plate 2 pressed together. Connectors 5 are provided between SOFC repeating units 7, between SOEC repeating units 8, and at the junctions of SOFC repeating units 7 and SOEC repeating units 8. These connectors 5 serve to conduct electricity in series, separate gases, and provide support. The thermo-electro-chemical coupled solid oxide fuel cell stack has through holes around its perimeter, which, when aligned, form a vertical common gas channel 13, specifically including: a fuel gas inlet 9 for transporting SOFC fuel (such as hydrogen or methane), a water vapor inlet 10 for transporting SOEC feedstock, a fuel gas outlet 12, and a hydrogen outlet 11. Crucially, the exhaust channel of the SOEC repeating unit 8 and the intake channel of the SOFC repeating unit 7 are topologically connected through the common gas channel 13. The oxygen generated by SOEC repeating unit 8 flows into the channel and then directly to the cathode inlet of SOFC repeating unit 7.

[0058] As shown in Figure 4, the anode side (lower part) of the SOFC repeating unit 7 includes a block-coupled SOFC anode seal 701 and a block-coupled SOFC anode current collector 702. Hydrocarbon fuel is introduced here to supply the SOFC anode 303. Battery core: The SOFC single cell 3 is encapsulated in the first block-coupled battery frame 703. The cathode side (upper part) of the SOFC repeating unit 7 includes a block-coupled SOFC cathode seal 704 and a block-coupled SOFC cathode current collector 705, which receives high-concentration oxygen from the SOEC block and supplies the SOFC cathode 301.

[0059] As shown in Figure 5, the anode side (lower part) of the SOEC repeating unit 8 includes a block-coupled SOEC anode seal 801 and a block-coupled SOEC anode current collector 802, where oxygen generated by electrolysis is collected and introduced into a common oxygen channel. The battery core: the SOEC single cell 4 is encapsulated in a second block-coupled battery frame 803. The cathode side (upper part) of the SOEC repeating unit 8 includes a block-coupled SOEC cathode seal 804 and a block-coupled SOEC cathode current collector 805, where high-temperature steam is introduced, and an electrolysis reaction occurs at the SOEC cathode 401.

[0060] Coupling advantages:

[0061] Thermal field control: By adjusting the stacking ratio of SOFC repeating unit 7 to SOEC repeating unit 8 (e.g., 4:3 alternation as shown in Figure 3), the temperature distribution inside the stack can be precisely controlled, and the heat generated by the SOFC block can be used to heat the upstream and downstream SOEC blocks.

[0062] Oxygen Utilization: Unlike the micro-permeation in Example 1, this example achieves inter-block oxygen transfer through a common oxygen channel. The SOEC block acts as an "oxygen generator," providing high-purity oxidant to the SOFC block, thereby increasing the output voltage of the SOFC block and further reducing the hydrogen production power consumption of the SOEC module from the original 3.3 kWh / Nm³. 3 Decreased to 0.6 kWh / Nm 3 .

Claims

1. A thermo-electro-chemically coupled solid oxide fuel cell stack, comprising a lower end plate (1) and an upper end plate (2), characterized in that: Several SOFC single cells (3) and SOEC single cells (4) are arranged between the lower end plate (1) and the upper end plate (2); the SOFC single cell (3) includes an SOFC cathode (301), an SOFC electrolyte (302) and an SOFC anode (303) pressed together in sequence; the SOEC single cell (4) includes an SOEC cathode (401), an SOEC electrolyte (402) and an SOEC anode (403) pressed together in sequence; the chamber where the SOEC anode (403) is located is connected to the chamber where the SOFC cathode (301) is located, and the oxygen generated by the electrolysis of the SOEC anode (403) can enter the SOFC cathode (301) side to participate in the reaction; the SOFC single cells (3) and SOEC single cells (4) are electrically connected in series through a connector (5) or a current collector.

2. The thermo-electro-chemically coupled solid oxide fuel cell stack according to claim 1, characterized in that: Several hybrid repeating units (6) are also provided between the lower end plate (1) and the upper end plate (2); the hybrid repeating unit (6) includes an alternating coupling SOFC anode seal (601), an alternating coupling SOFC anode current collector (602), a first alternating coupling battery frame (603) for fixing the SOFC single cell (3), a coupling chamber seal (604), a coupling chamber current collector (605), a second alternating coupling battery frame (606) for fixing the SOEC single cell (4), and an alternating coupling SOEC cathode seal (605). The alternating SOFC anode seal (601) and alternating SOFC anode current collector (602) are disposed on the connector (5) or the lower end plate (1), the coupling chamber seal (604) and coupling chamber current collector (605) are disposed between the SOFC single cell (3) and the SOEC single cell (4), and the SOEC cathode seal (607) and SOEC cathode current collector (608) are disposed on the second alternating coupling battery frame (606).

3. A thermo-electro-chemically coupled solid oxide fuel cell stack according to claim 2, characterized in that: The first alternating coupling battery frame (603), SOFC single cell (3), coupling chamber seal (604), SOEC single cell (4), and second alternating coupling battery frame (606) form an oxygen exchange chamber (609). The coupling chamber current collector (605) is placed in the oxygen exchange chamber (609). The oxygen generated by the SOEC anode (403) can be transferred to the SOFC cathode (301) through the oxygen exchange chamber (609).

4. A thermo-electro-chemically coupled solid oxide fuel cell stack according to claim 2, characterized in that: The SOFC anode (303) is disposed on the side of the first alternating coupled battery frame (603) near the alternating coupled SOFC anode current collector (602), and the SOFC cathode (301) is disposed on the side of the first alternating coupled battery frame (603) near the coupling chamber current collector (605).

5. A thermo-electro-chemically coupled solid oxide fuel cell stack according to claim 2, characterized in that: The SOEC anode (403) is disposed on the side of the second alternating coupled battery frame (606) near the coupling chamber current collector (605), and the SOEC cathode (401) is disposed on the side of the second alternating coupled battery frame (606) near the SOEC cathode current collector (608).

6. A thermo-electro-chemically coupled solid oxide fuel cell stack according to claim 1, characterized in that: Several SOFC repeating units (7) and SOEC repeating units (8) are also provided between the lower end plate (1) and the upper end plate (2). The SOFC repeating units (7) are separated from each other, from each other, and from each other by a connector (5).

7. A thermo-electro-chemically coupled solid oxide fuel cell stack according to claim 6, characterized in that: The SOFC repeating unit (7) includes a block-coupled SOFC anode seal (701), a block-coupled SOFC anode current collector (702), a first block-coupled battery frame (703) for fixing the SOFC single cell (3), a block-coupled SOFC cathode seal (704), and a block-coupled SOFC cathode current collector (705). The block-coupled SOFC anode seal (701) and the block-coupled SOFC anode current collector (702) are disposed on the connector (5) or the lower end plate (1). The block-coupled SOFC cathode seal (704) and the block-coupled SOFC cathode current collector (705) are disposed on the side of the first block-coupled battery frame (703) near the upper end plate (2).

8. A thermo-electro-chemically coupled solid oxide fuel cell stack according to claim 6, characterized in that: The SOEC repeating unit (8) includes a block-coupled SOEC anode seal (801), a block-coupled SOEC anode current collector (802), a second block-coupled battery frame (803) for fixing the SOEC single cell (4), a block-coupled SOEC cathode seal (804), and a block-coupled SOEC cathode current collector (805). The block-coupled SOEC anode seal (801) and the block-coupled SOEC anode current collector (802) are disposed on the connector (5), and the block-coupled SOEC cathode seal (804) and the block-coupled SOEC cathode current collector (805) are disposed on the side of the second block-coupled battery frame (803) near the upper end plate (2).

9. A thermo-electro-chemically coupled solid oxide fuel cell stack according to claim 7 or 8, characterized in that: The block-coupled SOFC anode seal (701), the first block-coupled battery frame (703), the block-coupled SOFC cathode seal (704), the block-coupled SOEC anode seal (801), the second block-coupled battery frame (803), the block-coupled SOEC cathode seal (804), and the connector (5) are all provided with through holes for forming a vertical common gas channel (13), so that the chamber where the SOEC anode (403) is located is connected to the chamber where the SOFC cathode (301) is located.

10. A thermo-electro-chemically coupled solid oxide fuel cell stack according to claim 6, characterized in that: The ratio of the number of SOFC repeating units (7) to the number of SOEC repeating units (8) is preset based on the target hydrogen production capacity, stack thermal balance calculation and stress field simulation results.

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