Electrochemical Cell Stack

Abstract

To reduce a temperature difference between a plurality of electrochemical cell stacks.SOLUTION: In an electrochemical cell stack 10, a plate-shaped electrochemical cell 11 is stacked. The electrochemical cell 11 generates electricity by the electrochemical reaction of fuel gas and oxidant gas. A fuel gas inlet 13 and a fuel gas outlet 14 are located on one of first outer surfaces S1 in the stacking direction of the electrochemical cell 11. An oxidant gas inlet 15 and an oxidant gas outlet 16 are located on a second outer surface S2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to electrochemical cell stacks. [Background technology]

[0002] Fuel cells are known that generate electricity through an electrochemical reaction between a fuel gas and an oxidant gas. Fuel cells are assembled into an electrochemical cell stack in which electrochemical cells, which are the smallest units for generating electricity, are stacked (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-225078 Summary of the Invention [Problem to be solved by the invention]

[0004] To improve power generation efficiency, it is preferable to minimize temperature variations among multiple stacked electrochemical cells, but it has been difficult to control the temperature of each individual electrochemical cell.

[0005] Therefore, an object of the present disclosure, made in consideration of the above-described problems of the conventional art, is to provide an electrochemical cell stack that reduces the temperature difference between a plurality of electrochemical cells. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, an electrochemical cell stack according to a first aspect comprises: An electrochemical cell stack in which plate-shaped electrochemical cells that generate electricity by an electrochemical reaction between a fuel gas and an oxidant gas are stacked, A fuel gas inlet and a fuel gas outlet are located on one first outer surface in the stacking direction of the electrochemical cell, and an oxidizer gas inlet and an oxidizer gas outlet are located on a second outer surface behind the first outer surface.

[0007] According to the electrochemical cell stack of the present disclosure configured as described above, the temperature difference between the plurality of electrochemical cells is reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view of an electrochemical cell stack according to a first embodiment. [Figure 2] FIG. 2 is a top view of the electrochemical cell stack of FIG. 1. [Figure 3] FIG. 2 is a cross-sectional view of the electrochemical cell of FIG. 1 taken along the thickness direction. [Figure 4] FIG. 4 is a cross-sectional view of the electrochemical cell taken along line IV-IV in FIG. [Figure 5] FIG. 4 is a cross-sectional view of the electrochemical cell taken along line VV in FIG. [Figure 6] FIG. 1 is a conceptual diagram illustrating gas flow paths in an electrochemical cell stack in which the gas inlet and outlet are located on the same surface. [Figure 7] FIG. 10 is a perspective view of an electrochemical cell stack according to a second embodiment. [Figure 8] FIG. 8 is a top view of the electrochemical cell stack of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of an electrochemical cell stack to which the present disclosure is applied will be described with reference to the drawings.

[0010] 1, an electrochemical cell stack 10 according to the first embodiment of the present disclosure is formed by stacking a plurality of plate-shaped electrochemical cells 11. The stacked electrochemical cells 11 may be sandwiched between a first end plate 12a and a second end plate 12b from both ends in the stacking direction.

[0011] The shape of the electrochemical cell stack 10 as viewed from the stacking direction may be any shape, for example, rectangular, hexagonal, circular, etc. In the first embodiment, the shape of the electrochemical cell stack 10 as viewed from the stacking direction is rectangular.

[0012] A fuel gas inlet 13 and a fuel gas outlet 14 are located on one first outer surface S1 in the stacking direction. An oxidizer gas inlet 15 and an oxidizer gas outlet 16 are located on a second outer surface S2 on the back side of the first outer surface S1 in the stacking direction.

[0013] 2, the fuel gas inlet 13 and the fuel gas outlet 14 may be located at opposite ends of the electrochemical cell stack 10 in a first direction d1 perpendicular to the stacking direction. The oxidant gas inlet 15 and the oxidant gas outlet 16 may be located at opposite ends of the electrochemical cell stack 10 in a second direction d2 perpendicular to the stacking direction. The second direction d2 may form an angle of less than 45° with the first direction d1.

[0014] In a configuration in which the outer edge of the first outer surface S1 includes two parallel sides, the fuel gas inlet 13 and the fuel gas outlet 14 may be located near the two sides, respectively. The oxidant gas inlet 15 and the oxidant gas outlet 16 may be located near the two sides, respectively, when viewed from the stacking direction.

[0015] When viewed from the stacking direction, the oxidant gas inlet 15 may be located closer to the fuel gas inlet 13 than the center of the line segment connecting the fuel gas inlet 13 and the fuel gas outlet 14. In this specification, the line segment connecting the inlet and the outlet may be the line segment connecting the centers of the inlet and the outlet. When viewed from the stacking direction, the oxidant gas outlet 16 may be located closer to the fuel gas outlet 14 than the center of the line segment connecting the fuel gas inlet 13 and the fuel gas outlet 14.

[0016] When viewed from the stacking direction, a line segment connecting the fuel gas inlet 13 and the fuel gas outlet 14 and a line segment connecting the oxidant gas inlet 15 and the oxidant gas outlet 16 may intersect. For example, when viewed from the stacking direction, the line segment connecting the fuel gas inlet 13 and the fuel gas outlet 14 may be inclined with respect to one side near the fuel gas inlet 13 at the outer edge of the first outer surface S1. When viewed from the stacking direction, the line segment connecting the oxidant gas inlet 15 and the oxidant gas outlet 16 may be inclined with respect to one side near the oxidant gas inlet 15 at the outer edge of the first outer surface S1.

[0017] The electrochemical cell stack 10 may be installed as part of a battery device so that the stacking direction is parallel to the vertical direction on the ground surface. Alternatively, the electrochemical cell stack 10 may be installed as part of a battery device so that the stacking direction is horizontal on the ground surface. In a configuration in which the electrochemical cell stack 10 is installed so that the stacking direction is horizontal, the fuel gas outlet 14 and the oxidant gas outlet 16 may be installed so that they are located higher than the fuel gas inlet 13 and the oxidant gas inlet 15.

[0018] 3, in the electrochemical cell 11, a plate-shaped electrolyte membrane 17 may be sandwiched between two interconnectors 20 from both membrane surface sides via a fuel electrode 18 and an air electrode 19. The space between the two interconnectors 20 may be sealed by a frame 21.

[0019] The electrochemical cell 11 may be a solid oxide fuel cell (SOFC), a polymer electrolyte fuel cell, a phosphoric acid fuel cell, or a molten carbonate fuel cell. The fuel electrode 18 and the air electrode 19 may be made of materials suitable for each system and may have a structure suitable for each system.

[0020] The interconnector 20 may be, for example, a metal plate having the same shape as the plate surface of the electrochemical cell 11. The interconnector 20 may be provided with a plurality of ridges 22 parallel to the plate surface. The interconnector 20 may be in contact with the anode 18 via the ridges 22. The interconnector 20 may be in contact with the cathode 19 via the ridges 22.

[0021] The frame 21 may be formed from an electrically insulating material. The frame 21 may be in the shape of a frame along the outer edge of the plate surface of the interconnector 20. The frame 21 may be in close contact with the plate surface near the outer edge of the two interconnectors 20, with the surfaces of the two interconnectors 20 on which the ridge portions 22 are provided facing each other.

[0022] 4 and 5, the frame 21 may be formed with a first fuel gas passage hole 23, a second fuel gas passage hole 24, a first oxidant gas passage hole 25, and a second oxidant gas passage hole 26 together with the interconnector 20. The first fuel gas passage hole 23, the second fuel gas passage hole 24, the first oxidant gas passage hole 25, and the second oxidant gas passage hole 26 may penetrate the frame 21 in the thickness direction, in other words, parallel to the axial direction of the frame.

[0023] As shown in Fig. 3, a fuel gas chamber FR is defined on the fuel electrode 18 side by the electrolyte membrane 17, the interconnector 20, and the frame 21. An oxidant gas chamber OR is defined on the air electrode 19 side by the electrolyte membrane 17, the interconnector 20, and the frame 21. As shown in Fig. 4, a hole may be formed in a part of the frame 21, thereby connecting the fuel gas chamber FR to the first fuel gas passing hole 23 and the second fuel gas passing hole 24. As shown in Fig. 5, a hole may be formed in a part of the frame 21, thereby connecting the oxidant gas chamber OR to the first oxidant gas passing hole 25 and the second oxidant gas passing hole 26.

[0024] The electrochemical cells 11 may be stacked such that the first fuel gas passage holes 23 of each electrochemical cell 11 are continuous, the second fuel gas passage holes 24 of each electrochemical cell 11 are continuous, the first oxidant gas passage holes 25 of each electrochemical cell 11 are continuous, and the second oxidant gas passage holes 26 of each electrochemical cell 11 are continuous. As shown in FIG. 1 , by stacking the electrochemical cells 11 in this manner, the first fuel gas passage holes 23 of all the electrochemical cells 11 may form a fuel gas inlet hole 27 parallel to the stacking direction. The first oxidant gas passage holes 25 of all the electrochemical cells 11 may form an oxidant gas inlet hole 28 parallel to the stacking direction. The second fuel gas passage holes 24 of all the electrochemical cells 11 may form a fuel gas outlet hole 29 parallel to the stacking direction. The second oxidant gas passage holes 26 of all the electrochemical cells 11 may form an oxidant gas outlet hole 30 parallel to the stacking direction.

[0025] The first end plate 12a may be located on the first outer surface S1 side. The second end plate 12b may be located on the second outer surface S2 side. The first end plate 12a may have a fuel gas inlet 13 and a fuel gas outlet 14 formed therein, each having a hole. The second end plate 12b may have an oxidizer gas inlet 15 and an oxidizer gas outlet 16 formed therein.

[0026] The fuel gas inlet 13 and the fuel gas supply hole 27 may be continuous. The fuel gas outlet 14 and the fuel gas discharge hole 29 may be continuous. The oxidant gas inlet 15 and the oxidant gas supply hole 28 may be continuous. The oxidant gas outlet 16 and the oxidant gas discharge hole 30 may be continuous.

[0027] The fuel gas supplied from the fuel gas inlet 13 may flow into each fuel gas chamber FR through the fuel gas supply holes 27. The oxidant gas supplied from the oxidant gas inlet 15 may flow into each oxidant gas chamber OR through the oxidant gas supply holes 28. Each electrochemical cell 11 generates electricity through an electrochemical reaction between the fuel gas supplied to the fuel gas chamber FR of each electrochemical cell 11 and the oxidant gas supplied to the oxidant gas chamber OR of each electrochemical cell 11.

[0028] In the electrochemical cell stack 10 of the first embodiment configured as described above, the fuel gas inlet 13 and the fuel gas outlet 14 are located on the first outer surface S1, and the oxidizer gas inlet 15 and the oxidizer gas outlet 16 are located on the second outer surface S2. For example, in a typical electrochemical cell stack, it is conceivable to position the fuel gas and oxidizer gas inlets and outlets on the same surface. In such a structure, as shown in FIG. 6 , the fuel gas and oxidizer gas flow from the inlet IN in one direction along the stacking direction, flow through each electrochemical cell 11′ in a direction perpendicular to the stacking direction, flow in the opposite direction to the stacking direction, and are discharged from the outlet OUT. In such a configuration, gases have difficulty reaching electrochemical cells 11′ far from the inlet IN and outlet OUT. This may result in a difference in the amount of heat exchanged between the heat generated by power generation and the gas compared to portions closer to the inlet IN and outlet OUT. This may result in a temperature difference along the stacking direction among the multiple electrochemical cells 11′. On the other hand, in the electrochemical cell stack 10 having the above-described configuration, the fuel gas flows in one direction in the stacking direction, and the oxidant gas flows in the opposite direction in the stacking direction. Therefore, in the electrochemical cell stack 10, the direction of the temperature change of each electrochemical cell 11 due to the fuel gas along the stacking direction is opposite to the direction of the temperature change of each electrochemical cell 11 due to the oxidant gas. Therefore, in the electrochemical cell stack 100, the temperature change of each electrochemical cell 11 along the stacking direction as a whole is canceled out by the sum of the temperature change due to the fuel gas and the temperature change due to the oxidant gas. As a result, the electrochemical cell stack 100 reduces the temperature difference between the multiple stacked electrochemical cells 11. Furthermore, in the electrochemical cell stack 10 having the above-described configuration, the fuel gas inlet 13 and the fuel gas outlet 14, and the oxidant gas inlet 15 and the oxidant gas outlet 16 can be positioned away from each other. Therefore, the electrochemical cell stack 10 provides increased design freedom to avoid interference between piping that connects separately to the fuel gas inlet 13 and fuel gas outlet 14, and the oxidant gas inlet 15 and oxidant gas outlet 16.

[0029] Furthermore, in the electrochemical cell stack 10 of the first embodiment, the fuel gas inlet 13 and outlet 14 are located at both ends of the electrochemical cell stack 10 in a first direction d1 perpendicular to the stacking direction, and the oxidant gas inlet 15 and outlet 16 are located at both ends of the electrochemical cell stack 10 in a second direction d2 perpendicular to the stacking direction and forming an angle of less than 45° with the first direction d1. With this configuration, the electrochemical cell stack 10 has the fuel gas inlet 13 and fuel gas outlet 14 located on the first outer surface S1 separated from each other, and the oxidant gas inlet 15 and oxidant gas outlet 16 located on the second outer surface S2 separated from each other, so that the inlets and outlets are close to each other and the degree of freedom in design is further improved to avoid interference between pipes connected separately to the inlets and outlets.

[0030] Furthermore, in the electrochemical cell stack 10 of the first embodiment, the oxidizer gas inlet 15 is located closer to the fuel gas inlet 13 than the center of the line segment connecting the fuel gas inlet 13 and outlet 14, as viewed in the stacking direction. With this configuration, when the electrochemical cell stack 10 is installed with the stacking direction horizontal as shown in FIG. 1 , the oxidizer gas inlet 15 and the oxidizer gas outlet 16 can be installed so that they are spaced apart and above the fuel gas inlet 13 and the oxidizer gas inlet 15, respectively. This further enhances the design flexibility of the electrochemical cell stack 10, allowing for interference between the piping separately connected to the inlet and outlet. Furthermore, when installed in this orientation, the electrochemical cell stack 10 allows the fuel gas and the oxidizer gas to flow vertically from below to above, thereby distributing the fuel gas throughout the entire fuel gas chamber FR and the oxidizer gas throughout the entire oxidizer gas chamber OR. Therefore, the electrochemical cell stack 10 can improve power generation efficiency.

[0031] Next, an electrochemical cell stack according to a second embodiment of the present disclosure will be described. In the second embodiment, the positions of the fuel gas inlet and outlet and the oxidant gas inlet and outlet are different from those of the first embodiment. The second embodiment will be described below, focusing on the differences from the first embodiment. Note that parts having the same configuration as those in the first embodiment are given the same reference numerals.

[0032] 7, in the electrochemical cell stack 100 of the second embodiment, a fuel gas inlet 130 and a fuel gas outlet 140 are located on one first outer surface S1 in the stacking direction, similar to the first embodiment. Also, an oxidant gas inlet 150 and an oxidant gas outlet 160 are located on a second outer surface S2, similar to the first embodiment.

[0033] As shown in FIG. 8 , the fuel gas inlet 130 and the fuel gas outlet 140 may be located at both ends of the electrochemical cell stack 100 in a first direction d1 perpendicular to the stacking direction, similar to the first embodiment. Unlike the first embodiment, the oxidant gas inlet 150 and the oxidant gas outlet 160 may be located at both ends of the electrochemical cell stack 100 in a third direction d3 perpendicular to the stacking direction. The angle between the third direction d3 and the first direction d1 may be 45° or more and 135° or less. More specifically, the angle between the third direction d3 and the first direction d1 may be 90°. Furthermore, the line segment connecting the fuel gas inlet 130 and the fuel gas outlet 140 may be perpendicular to one side near the fuel gas inlet 130 at the outer edge of the first outer surface S1. Furthermore, the line segment connecting the oxidant gas inlet 150 and the oxidant gas outlet 160 may be perpendicular to one side near the oxidant gas inlet 150 at the outer edge of the second outer surface S2.

[0034] In a configuration in which the outer edge of the first outer surface S1 includes two parallel sides, similar to the first embodiment, the fuel gas inlet 130 and the fuel gas outlet 140 may be located near the two sides, respectively. Unlike the first embodiment, in a configuration in which the first outer surface S1 is rectangular, the oxidant gas inlet 150 and the oxidant gas outlet 160 may be located near two sides connecting the two parallel sides on which the fuel gas inlet 130 and the fuel gas outlet 140 are provided, as viewed from the stacking direction.

[0035] In the electrochemical cell stack 100 of the second embodiment configured as described above, similar to the first embodiment, the fuel gas inlet 130 and the fuel gas outlet 140 are located on the first outer surface S1, and the oxidant gas inlet 150 and the oxidant gas outlet 160 are located on the second outer surface S2. Therefore, the electrochemical cell stack 100 reduces the temperature difference between the multiple stacked electrochemical cells 11. Furthermore, the electrochemical cell stack 100 improves the degree of freedom in design to avoid interference between pipes separately connected to the fuel gas inlet 13 and the fuel gas outlet 14, and the oxidant gas inlet 15 and the oxidant gas outlet 16.

[0036] Furthermore, in the electrochemical cell stack 100 of the second embodiment, the fuel gas inlet 130 and outlet 140 are located at both ends of the electrochemical cell stack 100 in a first direction d1 perpendicular to the stacking direction, and the oxidant gas inlet 150 and outlet 160 are located at both ends of the electrochemical cell stack 100 in a third direction d3 that is perpendicular to the stacking direction and forms an angle of 45° or more and 135° or less with the first direction d1. With this configuration, the electrochemical cell stack 100 has the fuel gas inlet 130 and fuel gas outlet 140 located on the first outer surface S1 separated from each other, and the oxidant gas inlet 150 and oxidant gas outlet 160 located on the second outer surface S2 separated from each other, further improving the degree of freedom in design to avoid interference between pipes connected separately to the inlet and outlet.

[0037] Those skilled in the art may make various modifications and alterations to the contents of the present disclosure based on the present disclosure. Therefore, these modifications and alterations are within the scope of the present disclosure. For example, in each embodiment, each functional unit, each means, each step, etc. may be added to other embodiments without logical inconsistency, or may be replaced with each functional unit, each means, each step, etc. of other embodiments. Furthermore, in each embodiment, multiple functional units, each means, each step, etc. may be combined into one or divided into separate units. Furthermore, each of the above-described embodiments of the present disclosure is not limited to faithful implementation of each described embodiment, but may also be implemented by combining each feature or omitting some features as appropriate.

[0038] For example, the areas of the oxidant gas inlets 15, 150 and outlets 16, 160, the oxidant gas inlets 28, and the oxidant gas outlets 30, as viewed from the stacking direction, may be larger than the fuel gas inlets 13, 130 and outlets 14, 140, the fuel gas inlets 27, and the fuel gas outlets 29. Oxidant gas (e.g., air) has a larger average molecular weight and therefore lower diffusibility than fuel gas (e.g., hydrogen-rich gas). In particular, oxidant gas tends to have a higher viscosity than fuel gas at higher temperatures. In SOFCs operated at relatively high temperatures (e.g., 700°C to 1000°C), the oxidant gas is less likely to diffuse than the fuel gas. Therefore, the above-described configuration can also address the problem of the fuel gas and the oxidant gas flowing in opposite directions in the stacking direction, resulting in insufficient offset of temperature changes in each electrochemical cell 11 along the stacking direction. [Explanation of symbols]

[0039] 10, 100 Electrochemical cell stack 11 Electrochemical Cell 12a First end plate 12b Second end plate 13, 130 Fuel gas inlet 14, 140 Fuel gas outlet 15, 150 Oxidant gas inlet 16, 160 Oxidant gas outlet 17 Electrolyte membrane 18 Fuel electrode 19 Air electrode 20 Interconnector 21 frames 22 Ridge 23 First fuel gas passage hole 24 Second fuel gas passage hole 25 First oxidant gas passage hole 26 Second oxidizer gas passage hole 27 Fuel gas supply hole 28 Oxidant gas supply hole 29 Fuel gas exhaust hole 30 Oxidant gas exhaust hole d1 First direction d2 Second direction FR fuel gas chamber OR Oxidizer gas chamber S1 First outer surface S2 Second outer surface

Claims

1. An electrochemical cell stack including plate-shaped electrochemical cells that generate electricity by an electrochemical reaction between a fuel gas and an oxidant gas, stacked and sandwiched between a first end plate and a second end plate, a fuel gas inlet and a fuel gas outlet are located on one of the first end plates in the stacking direction of the electrochemical cells, and an oxidant gas inlet and an oxidant gas outlet are located on the second end plate on the back side of the first end plate; the fuel gas inlet and the fuel gas outlet are located near two sides at both ends of the electrochemical cell stack in a first direction perpendicular to the stacking direction, the oxidant gas inlet and the oxidant gas outlet are located near two sides at both ends of the electrochemical cell stack that are perpendicular to the stacking direction and form a second angle with the first direction that is less than 45°; a line segment connecting the fuel gas inlet and the fuel gas outlet and a line segment connecting the oxidant gas inlet and the oxidant gas outlet intersect when viewed from the stacking direction, at least one of the fuel gas inlet and the fuel gas outlet, and the oxidant gas inlet and the oxidant gas outlet is located away from two sides connecting the two ends of the electrochemical cell stack, The fuel gas flow path from the fuel gas inlet to the fuel gas outlet includes: a fuel gas supply hole through which the fuel gas flows from the fuel gas inlet toward one direction in the stacking direction of the electrochemical cell stack; a flow path through which the fuel gas flows in a direction perpendicular to the stacking direction within the electrochemical cell; a fuel gas discharge hole through which the fuel gas flows in a direction opposite to the stacking direction, turning back and being discharged from the fuel gas outlet, The flow path of the oxidant gas from the oxidant gas inlet to the oxidant gas outlet includes: an oxidant gas supply hole through which the oxidant gas flows from the oxidant gas inlet in a direction opposite to the stacking direction; a flow path through which the oxidant gas flows in a direction perpendicular to the stacking direction within the electrochemical cell; an oxidant discharge hole through which the oxidant gas flows while turning back in one direction of the stacking direction and is discharged from an outlet of the oxidant gas. Electrochemical cell stack.

2. 10. The electrochemical cell stack of claim 1, The oxidant gas inlet is located closer to the fuel gas inlet than the center of a line segment connecting the fuel gas inlet and the fuel gas outlet when viewed from the stacking direction. Electrochemical cell stack.

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