Polymer electrolyte fuel cell stack

Abstract

Fuel cell stack (100) in which frame-integrated MEAs (120), each comprising an MEA (121) and a frame (123) enclosing the MEA (121) and having a coolant supply distribution hole (114), and Separator pairs (140), each comprising an anode separator (130A) and a cathode separator (130B), each having a corrugated central portion (131) forming channels and an outer peripheral portion (133) surrounding the central portion (131), positioned opposite one another in such a way as to bring the outer peripheral portions (133) into contact with one another, wherein the anode separator (130A) and the cathode separator (130B) have a coolant supply distribution hole (114) arranged on the outer peripheral portion (133) and coolant sealing elements (157) arranged on the back of the contact area of ​​the outer peripheral portion (133), are stacked on top of each other, with the frame (123) has recesses (124) receiving the coolant sealing elements (157), the separator pair (140) comprises coolant channels (141) consisting of opposite surfaces of the central portions (131) of the anode separator (130A) and the cathode separator (130B) and a coolant inlet channel (143) connecting the coolant channels (141) and the coolant supply distribution hole (114), an upper part of the coolant inlet channel (143) consists of an inlet groove (135A) formed on an opposite surface (133A) of the outer peripheral portion (133) of the anode separator (130A) and communicating with the coolant supply distribution hole (114), a lower part of the coolant inlet channel (143) consists of an inlet groove (135B) formed on an opposite surface of the outer peripheral portion (133B) of the cathode separator (130B) and communicating with the central portion (131), a coolant sealing member (157A) arranged on the back of the contact area of ​​the outer peripheral portion (133A) of the anode separator (130A), the coolant supply distribution hole (114) and the groove (135A) and a coolant sealing element (157B) arranged on the back of the contact area of ​​the outer peripheral portion (133B) of the cathode separator (130B) encloses the coolant supply distribution hole (114), wherein the inlet groove (135A) of the anode separator (130A) does not directly connect the coolant supply distribution hole (114) to the central portion (131A), and wherein the inlet groove (135B) of the cathode separator (130B) does not directly connect the coolant supply distribution hole (114) to the central portion (131B), wherein, when the frame-integrated MEAs (120) and the separator pairs (140) are stacked on top of each other, the inlet groove (135A) of the anode separator (130A) and the inlet groove (135B) of the cathode separator (130B) partially overlap.

Description

field of technology

[0001] The present invention relates to a polymer electrolyte fuel cell stack and a separator pair for the polymer electrolyte fuel cell stack. The present invention is particularly characterized by the structure of coolant inlet channels, coolant discharge channels, and coolant sealing elements for thinner structuring of polymer electrolyte fuel cells. State of the art

[0002] A polymer electrolyte fuel cell stack (hereinafter also referred to simply as a "fuel cell stack") comprises a cell laminate in which several individual cells are stacked and arranged in series. Each individual cell consists of a membrane electrode assembly (MEA) and a pair of separators arranged on either side of the membrane electrode assembly. The MEA comprises a polymer electrolyte membrane and a pair of catalyst electrodes (anode and cathode) arranged on either side of the polymer electrolyte membrane. The separator has gas channels for supplying fuel or oxidizing gas. It also has coolant channels through which the coolant flows to control the temperature of the fuel cell stack during operation.

[0003] In the fuel cell stack, pressure is applied in the lamination direction to ensure sealing of fluid (reaction gas or coolant) between cells and to reduce contact resistance between cells.

[0004] As described above, the separator has channels for the flow of reaction gas (fuel or oxidizing gas) or coolant. The fuel and oxidizing gases, as well as the coolant, are intended to flow through independent channels, so the fuel cell stack has sealing elements to seal the areas between each two channels (see, for example, Patent Document 1).

[0005] Fig. Fig. 1 shows a perspective exploded view of a fuel cell stack 1 disclosed in Patent Document 1. In the fuel cell stack 1, as shown in Fig. As shown in Figure 1, the single fuel cells 2, each consisting of a frame-integrated MEA 14 consisting of an MEA and a frame surrounding an outer periphery of the MEA, and a pair of separators (anode separator 15A and cathode separator 15B) sandwiching the frame-integrated MEA, are stacked one on top of the other. The separators comprised in a fuel cell stack 1 according to Patent Document 1 are metal separators formed by corrugating metal sheets through press processing.

[0006] Fig. Figure 2A shows an expanded view of a rear surface of the anode separator 15A opposite a frame-integrated MEA 14. The anode separator 15A has, as shown in Fig. 2A, a central portion 41 on which channels are formed, and an outer peripheral portion 43 surrounding the central portion 41. The outer peripheral portion 43 has a coolant supply manifold hole 22 through which the coolant passes, and a coolant inlet channel 51 connecting the coolant supply manifold hole 22 and coolant channels. Furthermore, the anode separator 15A has sealing elements 28B to prevent the coolant from leaking outward from the coolant inlet channel 51.

[0007] Fig. Figure 2B shows an expanded view of the surface of the cathode separator 15B opposite the frame-integrated MEA 14. The cathode separator 15B also has, as in Fig. 2B, a central portion 41 on which channels are formed, and an outer peripheral portion 43 surrounding the central portion 41. The outer peripheral portion 43 has an oxidizing gas supply manifold hole 23 through which the oxidizing gas passes, and an oxidizing gas inlet channel 61 connecting the oxidizing gas supply manifold hole 23 and oxidizing gas channels. Furthermore, the cathode separator 15B has a sealing member 28C to prevent the oxidizing gas from leaking out from the oxidizing gas inlet channel 61.

[0008] Fig. 3A shows a fuel cell stack 1 disclosed in Patent Document 1 in cross section along the line AA in Fig. 2A and Fig. 2B. In the fuel cell stack 1, as shown in Fig. 3A, sealing elements (27, 28B) are arranged between the adjacent outer peripheral sections of the anode separator 15A and the cathode separator 15B. Therefore, in the fuel cell stack 1, the adjacent outer peripheral sections of the anode separator 15A and the cathode separator 15B are not in direct contact with each other.

[0009] Furthermore, a concave and convex profile (31, 32) is provided on each of the outer peripheral portions of the separators in order to prevent twisting of the separator when pressure is applied in the lamination direction (hereinafter also simply referred to as "clamping pressure").

[0010] If the outer peripheral portions of the separators do not have a concave and convex profile (31, 32), as in Fig. 3B, the separators are rotated when clamping pressure is applied so that the coolant inlet channel 51, oxidizing gas inlet channel 61 or the like can be closed.

[0011] It is also a known prior art to form channels connecting the reaction gas distributors and the reaction gas channels inside a separator (see, for example, Patent Documents 2 and 3) or to provide sealing elements between areas with height difference provided on the outer peripheral portion of a separator (see, for example, Patent Documents 4 and 5) in order to restrict thickness in the lamination direction and at the same time prevent leakage of reaction gas through a space between an MEA and a separator.

[0012] It is also a known prior art to arrange sealing elements on recesses provided on a surface of a cathode separator opposite the MEA (see, for example, patent documents 6 and 7) in order to prevent twisting of the MEA by the sealing elements. List of citationsPatent literature Patent Document 1: Disclosure of Japanese Patent Application JP 2006 - 147 258 A Patent Document 2: Disclosure of Japanese Patent Application JP 2003 - 197 221 A Patent Document 3: Disclosure of US Patent Application US 2005 / 0 238 942 A1 Patent Document 4: Disclosure of Japanese Patent Application JP 2004 - 63 094 A Patent Document 5: Disclosure of US Patent Application US 2005 / 0 089 745 A1 Patent Document 6: Disclosure of Japanese Patent Application JP 2007 - 329 125 A Patent Document 7: Disclosure of US Patent Application US 2007 / 0 275 288 A1 Summary of the inventionTechnical problem

[0013] However, with regard to the fuel cell stack 1 disclosed in Patent Document 1, where the sealing elements are respectively disposed between the abutting separators, the clamping pressure causes the separators to twist slightly, even though a concave and convex profile is provided to prevent twisting. When the separators are twisted, the sealing reliability decreases, allowing the reaction gas or coolant to leak to the outside.

[0014] Furthermore, as in the fuel cell stack 1 disclosed in Patent Document 1, when the outer peripheral portions forming a coolant or reactant gas inlet channel have a concave and convex profile to prevent twisting, the pressure loss at the coolant or reactant gas inlet channel is increased, so that there is a possibility of precluding supply of a sufficient amount of fluid to the coolant or reactant gas channels.

[0015] In order to solve this problem, it is conceivable to bring the outer peripheral sections of the adjacent separators into contact with each other without arranging sealing elements between the adjacent separators (see Fig. 4 and Fig. 5).

[0016] Fig. Figure 4 shows a perspective view of a separator 130A and a separator 130B adjacent to each other in a fuel cell stack. Both separator 130A and separator 130B each have a fuel gas supply manifold hole 110, an oxidizing gas supply manifold hole 112, a coolant supply manifold hole 114, a fuel gas discharge manifold hole 111, an oxidizing gas discharge manifold hole 113, and a coolant discharge manifold hole 115 at an outer peripheral portion 133.

[0017] In the Fig. 4, a separator pair 140 is constructed in which the outer peripheral portions of the adjacent separators 130A and 130B may be opposed to each other in such a way that they are in contact with each other.

[0018] Furthermore, the outer peripheral portion 133A has, on the surface opposite to the separator 130B (hereinafter also simply referred to as “opposite surface”) of the separator 130A, coolant inlet channels 143 connecting a central portion 131A and the coolant supply manifold hole 114, and coolant discharge channels 145 connecting a central portion 131A and the coolant discharge manifold hole 115 (see FIG. Fig. 5 and Fig. 6). On the other hand, the outer peripheral portion 133A is flat without coolant inlet and coolant discharge channels.

[0019] The separator 130A has, on the rear surface of the opposite surface of the outer peripheral portion 133A (hereinafter also simply referred to as “rear surface”), fuel gas sealing elements 153A surrounding the fuel gas supply distribution hole 110 and the fuel gas discharge distribution hole 111, oxidizing gas sealing elements 155A surrounding the oxidizing gas supply distribution hole 112 and the oxidizing gas discharge distribution hole 113, and coolant sealing elements 157A surrounding the coolant supply distribution hole 114 and the coolant discharge distribution hole 115.

[0020] On the other hand, the separators 130A and 130B do not have a sealing element on the opposite side. Furthermore, Fig. 4, the outer peripheral portions 133 of the separators 130A and 130B are in contact with each other. On the other hand, the separators 130A and 130B are not in contact with each other at the coolant inlet channels 143 and the coolant discharge channels 145 to ensure coolant flow.

[0021] In this way, twisting of separators and reduction of sealing reliability caused by clamping pressure can be prevented by bringing the outer peripheral portions of the separators 130A and 130B into contact with each other.

[0022] Furthermore, the rear surface of the outer peripheral portion 133A of the separator 130A has a rear area Y (hereinafter also referred to as "low area Y"), a region for contacting the opposing surfaces of the separators 130A and 130B (hereinafter also simply referred to as "contact area"), and a raised area X (hereinafter also simply referred to as "high area X") compared to the low area Y. The high area X is an area formed by the coolant inlet channels 143 and the coolant discharge channels 145 toward the rear surface. In other words, the high area X means an area remote from the contact area.

[0023] In Fig. 4, the coolant sealing element 157A is arranged on the high surface X.

[0024] However, if you look at the Fig. 4, the fuel cell stack increases in the lamination direction of cells, which makes it difficult to reduce the size of the fuel cell stack. In the following, with reference to Fig. 5 and Fig. 6 explains why the reduction of the fuel cell stack in Fig. 4 shown separator pair 140 is difficult.

[0025] Fig. 5 shows a Fig. 4, having separator pairs 140, fuel cell stack in cross section along the line β in Fig. 4, and Fig. 6 one in Fig. 4, having separator pairs 140, fuel cell stack in cross section along the line γ in Fig. 4.

[0026] When in Fig. 5 and Fig. In the fuel cell stack shown in Figure 6, the frame-integrated MEAs 120 and the separator pairs 140 are stacked on top of each other, with two separators (separator 130A and separator 130B) being arranged opposite each other in such a way that their outer peripheral portions are in contact with each other.

[0027] A frame-integrated MEA 120 comprises an MEA 121 and a frame 123 enclosing the MEA 121. The frame 123 has recesses 124 that retain the sealing elements 157.

[0028] A separator pair 140 has, as in Fig. 5 and Fig. 6, coolant inlet channels 143 connecting the coolant channels 141 and the coolant supply manifold hole 114.

[0029] Furthermore, the sealing elements 157A are formed on the high surface X. When the sealing elements are arranged in this way on the high surface X, the thickness T1 of a separator pair 140 including the sealing elements cannot be smaller than the sum of the depth of the coolant inlet channels 143 and the thickness of the sealing elements 157.

[0030] Furthermore, when the sealing elements 157A are arranged in this way on the high surface X, it is necessary to make the frame of the frame-integrated MEA 120 thick. When the sealing elements 157A, as in Fig. 5 and Fig. 6, are arranged on the high surface X, the thickness of the frame 123 is the thinnest at the area 122 where the recesses 124 receiving the sealing elements 157 are provided (hereinafter also referred to as “the thinnest section”).

[0031] The frame 123 can only be formed if it has a certain thickness or more. If the material of the frame 123 is, for example, polyphenylene sulfide (PPS), it is difficult to make it thinner than 0.5 mm. Therefore, the thickness of the thinnest section 122 should be set to 0.5 mm or more. Therefore, the thickness T2 of a frame 123 cannot be less than the sum of the depth of the coolant inlet channels 143, the height of the sealing elements, and the thickness of the thinnest section 122 (e.g., 0.5 mm).

[0032] Furthermore, such a coolant inlet channel 143 may be flattened by the sealing elements, so that it is necessary to reinforce it with a concave and convex profile 31. In a Fig. 4 to 6, a problem of increased pressure loss at the coolant inlet channel 143 due to the concave and convex profile 31 therefore remains unsolvable.

[0033] Since the sealing elements 157A arranged in this way on the high surface X lead to an increase in the thickness T1 of the separator pair 140 and the thickness T2 of the frame 123, the fuel cell stack increases in the lamination direction of cells.

[0034] To achieve this objective, it is conceivable to arrange the coolant sealing elements 157A on the low surface Y. However, in order to arrange the coolant sealing element 157A surrounding the coolant supply distribution hole on the low surface Y, a formation of a low surface Y passing through the coolant inlet channels 143 is required. If a low surface Y passing through the coolant inlet channels 143 is arranged on a Fig. 4 to 6, the coolant inlet channels 143 are closed so that the coolant cannot flow into the coolant channels 141. Technical solution

[0035] The object of the present invention is to provide a fuel cell stack that can be reduced in size in the lamination direction of cells, wherein coolant sealing elements are arranged on the low surface Y. [1] A fuel cell stack in which frame-integrated MEAs, each comprising an MEA and a frame surrounding the MEA and having a coolant supply manifold hole; and pairs of separators, each comprising an anode separator A and a cathode separator B, each having a corrugated central portion forming channels and an outer peripheral portion surrounding the central portion, are placed opposite each other so as to bring the outer peripheral portions into contact with each other, and the anode separator A and the cathode separator B have a coolant supply hole arranged on the outer peripheral portion and coolant sealing elements arranged on the back of the contact area of ​​the outer peripheral portion; are stacked on each other, wherein the frame has recesses that accommodate the coolant sealing elements, the separator pair comprises coolant channels consisting of opposite surfaces of the central portions of the anode separator A and the cathode separator B, and a coolant inlet channel connecting the coolant channels and the coolant supply manifold hole, an upper part of the coolant inlet channel consists of an inlet groove A formed on an opposite surface of the outer peripheral portion of the anode separator A and communicating with the coolant supply manifold hole, a lower part of the coolant inlet channel consists of an inlet groove B formed on an opposite surface of the outer peripheral portion of the cathode separator B and communicating with the central portion, a coolant sealing member A arranged on the back side of the contact area of ​​the outer peripheral portion of the anode separator A encloses the coolant supply manifold hole and the groove A, and a coolant sealing member B arranged on the back side of the contact area of ​​the outer peripheral portion of the cathode separator B encloses the coolant supply manifold hole. The inlet groove of the anode separator does not directly connect the coolant supply manifold hole to the central section, and the inlet groove of the cathode separator does not directly connect the coolant supply manifold hole to the central section. When the frame-integrated MEAs and separator pairs are stacked, the inlet groove of the anode separator and the inlet groove of the cathode separator partially overlap. [2] The fuel cell stack according to [1], wherein the area surrounded by the coolant sealing element A includes that surrounded by the coolant sealing element B, and the coolant sealing element A and the coolant sealing element B do not overlap. [3] The fuel cell stack according to [1] or [2], wherein the outer peripheral portion further comprises a coolant discharge manifold hole, wherein the separator pair further comprises a coolant discharge channel connecting the coolant channels and the coolant discharge manifold hole, an upper part of the coolant inlet channel consists of an outlet groove B formed on the opposite surface of the outer peripheral portion of the metal separator B and communicating with the central portion, and a lower part of the coolant inlet channel consists of an outlet groove A formed on the opposite surface of the outer peripheral portion of the metal separator A and communicating with the metal separator A and metal separator. Advantageous effects of the invention

[0036] According to the invention, the coolant sealing elements surrounding the coolant distribution hole can be arranged on a low surface, allowing the frame and separator pairs to be made thin. Therefore, the fuel cell stack can be reduced in size in the cell lamination direction. Short description of the drawings Fig. 1 shows a perspective exploded view of a conventional fuel cell stack; Fig. 2A: a plan view of a conventional metal separator; Fig. 2B: a top view of a conventional metal separator; Fig. 3A: a cross-section of a conventional fuel cell stack; Fig. 3B: a cross-section of a conventional fuel cell stack; Fig. 4: a perspective exploded view of a pair of separators without sealing elements between adjacent separators; Fig. 5: a cross-section of a fuel cell stack with the Fig. 4 disclosed separator pairs; Fig. 6: a cross-section of a fuel cell stack with the Fig. 4 disclosed separator pairs; Fig. 7: a perspective view of a fuel cell stack according to the invention; Fig. 8: a cross-section of the fuel cell stack according to the invention; Fig. 9: a perspective exploded view of the fuel cell stack according to the invention; Fig. 10: a perspective exploded view of a separator pair according to the invention; Fig. 11: a perspective expanded view of the separator pair according to the invention near a coolant supply manifold hole; Fig. 12: an expanded view of the separator pair according to the invention in cross section; Fig. 13: an expanded view of the separator pair according to the invention in cross section; Fig. 14: a perspective expanded view of the separator pair according to the invention near a coolant discharge manifold hole; Fig. 15: an expanded view of the separator pair according to the invention in cross section; and Fig. 16: an expanded view of the separator pair according to the invention in cross section. Description of the embodiments

[0037] The invention relates to a fuel cell stack in which polymer electrolyte fuel cells are stacked one upon the other. The fuel cell stack according to the invention is characterized in that innovative structural measures for coolant inlet channels connecting a coolant supply manifold and coolant channels enable a reduction in the size of the fuel cell stack.

[0038] In the fuel cell stack according to the invention, (1) frame-integrated membrane electrode assemblies (hereinafter also referred to simply as "MEAs") and (2) separator pairs are stacked one on top of the other. The fuel cell stack according to the invention can additionally have current collector or end plates (see Fig. 7). (1) MEA integrated with frame

[0039] The frame-integrated MEA consists of (a) an MEA (membrane electrode assembly) and (b) a frame. a) MEA (membrane electrode assembly)

[0040] The MEA comprises a polymer electrolyte membrane and a pair of catalyst electrodes clamped between the polymer electrolyte membrane. The catalyst electrodes consist of an anode and a cathode. The catalyst electrode preferably comprises a catalyst layer adjacent to the polymer electrolyte membrane and a gas diffusion layer laminated to the catalyst layer.

[0041] A polymer electrolyte membrane is a polymer membrane that selectively transfers protons in a wet state. The material of the polymer electrolyte membrane is not particularly limited as long as it selectively transfers protons. Examples of these materials include fluorine- or hydrocarbon-containing polymer electrolyte membranes, and the like. Specific examples of fluorine-containing polymer electrolyte membranes include Nafion (registered trademark) of Dupont, Flemion (registered trademark) of Asahi Glass Co., Ltd., Aciplex (registered trademark) of Asahi Kasei Co., and GORE-SELECT (registered trademark) of Japan Gore-Tex Inc., among others.

[0042] The catalyst layer is a layer comprising a catalyst that accelerates the redox reaction of hydrogen or oxygen. The catalyst layer is not particularly limited if it is conductive and has catalytic activity to accelerate the redox reaction of hydrogen or oxygen. The catalyst layer on the cathode side contains, for example, platinum, a platinum-cobalt alloy, a platinum-nickel-cobalt alloy, or the like as a catalyst. The catalyst layer on the anode side contains platinum or a platinum-ruthenium alloy or the like as a catalyst.

[0043] The catalyst layer is prepared, for example, by mixing a proton-conductive electrolyte and a water-repellent resin such as PTFE with carbon particles such as acetylene black, Ketjenblack or Vulcan, on which one of the above-mentioned catalysts is supported, and the mixture is applied to the polymer electrolyte membrane.

[0044] The gas diffusion layer is arranged on top of the catalyst layer and exhibits air permeability for fuel or oxidizing gas and electronic conductivity. The gas diffusion layer can be a woven or nonwoven fabric made of carbon fibers or a porous sheet made of carbon particles and a binder. Grooves forming reaction gas channels for the reaction gas to be supplied to the catalyst layer can also be formed on the gas diffusion layer. b) Frame

[0045] The frame is an element that encloses the outer periphery of the MEA and holds it in place. The frame supports the MEA in such a way that the catalyst electrode can be in contact with the separator.

[0046] The frame is preferably heat- and acid-resistant and is typically made of resin. Examples of such frame materials include polypropylene, polyphenylene sulfide (PPS), polypropylene glycol, and the like.

[0047] The frame has a fuel gas supply manifold hole for supplying fuel gas, a fuel gas discharge manifold hole for discharging fuel gas, an oxidant gas supply manifold hole for supplying oxidant gas, an oxidant gas discharge manifold hole for discharging oxidant gas, a coolant supply manifold hole for supplying coolant, and a coolant discharge manifold hole for discharging coolant.

[0048] The frame also has recesses to accommodate the sealing elements provided on the separators described below (see Fig. 12, reference numeral 124). The frame has recesses for receiving the sealing elements, so that the MEA integrated with the frame and the separator pair can be positioned more easily during their lamination.

[0049] The frame may also be manufactured by 1) providing a mold with cavities shaped in the form of frames, and 2) filling, cooling, and hardening the frame material as mentioned above. (2) Separator pair

[0050] The separator pair comprises two separators (separators A and B). One of the separators A and B is an anode separator, and the other a cathode separator. According to the invention, separator A can be an anode separator and separator B a cathode separator; or, alternatively, separator A can be a cathode separator and separator B a fuel electrode separator.

[0051] The separators are metal separators, each manufactured by corrugating the metal sheet. Separators A and B each have a central section, an outer peripheral section, and sealing elements.

[0052] The central section is an area for forming reaction gas and coolant channels. Furthermore, a section for reaction gas distribution and a section for coolant distribution can be formed on it. According to the invention, it is possible to corrugate both the central sections of the two separators A and B (see embodiment 1 in Fig. 8), as well as to corrugate the central portion of one of the separators A and B alone and to make the other flat. When the central portion of one of the separators A and B alone is corrugated, grooves forming reaction gas channels are formed on the gas diffusion layer.

[0053] The outer peripheral portion is an area that includes the edge of the separator and encloses the central portion. The outer peripheral portion includes a fuel gas supply manifold hole for supplying fuel gas, a fuel gas discharge manifold hole for discharging fuel gas, an oxidant gas supply manifold hole for supplying oxidant gas, an oxidant gas discharge manifold hole for discharging oxidant gas, a coolant supply manifold hole for supplying coolant, and a coolant discharge manifold hole for discharging coolant. Furthermore, the outer peripheral portion includes inlet grooves forming the coolant inlet channels to be described below, and outlet grooves forming the coolant discharge channels to be described below.

[0054] The separator pair according to the invention is a conductive element manufactured by opposing separators A and B in such a way that the outer peripheral portions are brought into contact with each other. The separators A and B constituting the separator pair can be bonded or unbonded. In the separator pair, the opposing surfaces of the separators A and B are hereinafter referred to as "opposing surfaces." On the other hand, the rear surfaces of the opposing surfaces of the separators A and B are also referred to as "rear surfaces."

[0055] Furthermore, in the separator pair according to the invention, the opposite surface on the outer peripheral portion of the separator A is in contact with that on the outer peripheral portion of the separator B. A region where the opposite surface of the outer peripheral portion of the separator A is in contact with that of the outer peripheral portion of the separator B is hereinafter referred to as a "contact region."

[0056] The separator pair has reaction gas and coolant channels. The reaction gas channels are formed by the rear surfaces of the central sections of separators A and B, while the coolant channels are formed by the opposite surfaces of the central sections of separators A and B.

[0057] The separator pair further comprises coolant inlet channels connecting the coolant channels and the coolant supply distribution hole, and coolant discharge channels connecting the coolant channels and the coolant discharge distribution hole. The separator pair may additionally comprise coolant distribution sections between the coolant inlet channels and the coolant channels, as well as between the coolant discharge channels and the coolant channels (see Fig. 12 and Fig. 15). The number of coolant inlet and coolant outlet channels comprising a separator pair is not particularly limited, and is usually 10 to 15.

[0058] The coolant inlet and outlet channels are formed by the inlet and outlet grooves as described above. Specifically, the inlet and outlet grooves are formed on the opposite surfaces of the outer peripheral portions. The present invention is characterized in that, by means of innovative measures on the structure of the inlet and outlet grooves, the low surface, which passes through the coolant inlet and outlet channels in plan view, is designed on the rear surfaces of the separators without closing the coolant inlet and outlet channels. Here, "low surfaces" mean the areas of the rear surfaces of the separators A and B on the back side of the contact areas, as well as the areas at the same level as the areas on the back side of the contact areas on the areas of the rear surfaces of the separators A and B.The structure of inlet and exhaust grooves is explained below. a) On the structure of inlet grooves

[0059] The present invention is characterized in that the structure of the inlet grooves A of the separator A is different from that of the inlet grooves B of the separator B.

[0060] Specifically, the inlet grooves A of separator A communicate with the coolant supply manifold hole, not with the central portion forming the coolant channels. Therefore, the rear surface of separator A has a low area between the inlet grooves A and the central portion. On the other hand, the inlet grooves B of separator B communicate with the central portion forming the coolant channels, not with the coolant supply manifold hole (see Fig. Fig. 10 and Fig. 12). The rear surface of the separator B thus has a low area between the coolant supply manifold hole and the inlet grooves B.

[0061] Therefore, the upper part of the coolant inlet channel consists of the inlet groove A, and the lower part of the coolant inlet channel consists of the inlet groove B. Furthermore, the low surface that passes through the coolant inlet channels in the plan view of the separator pair is designed on the rear surfaces of the separators A and B.

[0062] Furthermore, the inlet grooves A and B are connected to each other. Thus, the coolant inlet channels connecting the coolant supply distribution hole and the central portion are formed. b) On the structure of exhaust grooves

[0063] In the same way as the inlet grooves, the present invention is characterized in that the structure of the outlet grooves A of the separator A is different from that of the outlet grooves B of the separator B.

[0064] For example, the outlet grooves A of separator A communicate with the coolant discharge manifold hole, not with the central portion forming the coolant channels; the outlet grooves B of separator B communicate with the central portion forming the coolant channels, not with the coolant discharge manifold hole. Otherwise, the outlet grooves A of separator A communicate with the central portion forming the coolant channels, not with the coolant discharge manifold hole; the outlet grooves B of separator B communicate with the coolant discharge manifold hole, not with the central portion forming the coolant channels.

[0065] Therefore, the upper part of the coolant outlet channel consists of the outlet groove A, and its lower part consists of the outlet groove B; otherwise, the upper part of the coolant discharge channel consists of the outlet groove B, and the lower part of the coolant discharge channel consists of the outlet groove A. Furthermore, the low surface that passes through the coolant discharge channels in the plan view of the separator pair is designed on the rear surfaces of the separators A and B.

[0066] Furthermore, the outlet grooves A and B are connected to each other. Thus, the coolant discharge channels connecting the central portion and the coolant supply distribution hole are formed.

[0067] In this way, the sections upstream and downstream of the coolant inlet and coolant discharge channels are designed by the grooves formed on different separators, so that the low surface passing through the coolant discharge channels in plan view of the separator pair can be designed without closing the coolant inlet and coolant discharge channels.

[0068] The sealing elements are elements for sealing the reactant gas and coolant. The sealing elements include outer peripheral sealing elements provided on the outer periphery of a separator; fuel gas sealing elements that enclose the fuel gas supply manifold hole and the fuel gas exhaust manifold hole; oxidizing gas sealing elements that enclose the oxidizing gas supply manifold hole and the oxidizing gas exhaust manifold hole; and coolant sealing elements that enclose the coolant supply manifold hole and the coolant exhaust manifold hole.

[0069] The present invention is characterized in that the sealing elements are arranged only on the rear surfaces of the outer peripheral sections, and not on the opposing surfaces. The outer peripheral section of separator A is therefore in contact with that of separator B. When the outer peripheral section of separator A is in contact with that of separator B, rotation of the separators is prevented even when clamping pressure is applied. Thus, the sealing for the separator pair according to the invention is particularly reliable.

[0070] Furthermore, in the present invention, separators A and B have the low surface that passes through the coolant inlet and coolant discharge channels in a plan view of the separator pair. Therefore, in the present invention, the coolant sealing elements surrounding the coolant supply manifold hole and the coolant discharge manifold hole can be arranged on the low surface (back of the contact areas).

[0071] For example, when arranging the coolant sealing elements A of the separator A on the low surface, it is possible to arrange them so that they enclose the coolant supply distribution hole and the inlet grooves A. When arranging the coolant sealing elements B of the separator B on the low surface, it is possible to arrange them so that they only enclose the coolant supply distribution hole.

[0072] In this way, the thickness of the separator pair can be reduced by arranging the coolant sealing elements on the low surfaces of the outer peripheral sections. Furthermore, by arranging the coolant sealing elements on the low surface of the outer peripheral sections, it is possible to arrange all the sealing elements (outer peripheral sealing elements, fuel gas sealing elements, and oxidizing gas sealing elements) on an identical surface (one low surface). Arranging all the sealing elements on an identical surface allows for a consistent design of the cross-section and compressibility of the entire sealing elements, which can prevent variations in fatigue life between different sealing elements.

[0073] Furthermore, the coolant sealing elements A and B preferably do not overlap in a plan view of the separator pair. Overlapping of the coolant sealing elements A and B can be prevented, e.g., by containing or separating a region of the separator B surrounded by the coolant sealing elements B from a region of the separator A surrounded by the coolant sealing elements A.

[0074] By preventing the A and B separators from overlapping, the thinnest section of the frame of the frame-integrated MEA can be reduced, thus increasing the frame's strength. This ensures the strength of the material without thickening the frame, allowing for a thinner frame structure.

[0075] The material of sealing elements is not particularly limited as long as it has elasticity, and can be either a thermosetting material or a thermoplastic material. Examples of thermosetting materials include silicone rubber (VQM), ethylene propylene rubber (EPDM), fluorocarbon rubber (FKM), and the like. Examples of thermoplastic materials include elastomers and the like.

[0076] Furthermore, the outer peripheral portions in the area near the sealing elements are preferably smooth and flat. Specifically, the outer peripheral portions in the area at intervals of 0.5 mm or less are preferably smooth. If the area near the sealing elements were not smooth, there would be a risk of the sealing elements leaking from the mold during casting, which could prevent press-forming into the desired profile. If the area near the sealing elements were not smooth, it would be difficult to produce a mold according to the profile of the sealing elements.

[0077] In this way, the thickness of the separator pair and frame can be made thin, so that the length of the fuel cell stack in the lamination direction can be reduced. Thus, the fuel cell stack can be reduced in size according to the invention.

[0078] The effects of the invention will be explained in more detail with reference to the drawings. The fuel cell stack according to the invention is described below.

[0079] Fig. 7 shows a perspective view of the fuel cell stack 100 according to the invention. The fuel cell stack 100 has, as in Fig. 7, several stacked individual cells. The cell laminate of individual cells is clamped by end plates 107 and secured with a fastening bolt 108 and a nut 109.

[0080] The fuel cell stack 100 further includes a fuel gas supply port 101, a coolant supply port 102, an oxidizing gas supply port 103, a fuel gas discharge port 104, a coolant discharge port 105, and an oxidizing gas discharge port 106 on one of the end plates 107. The fuel gas supply port 101 is coupled to a fuel gas supply manifold; the coolant supply port 102 is coupled to a coolant supply manifold; the oxidizing gas supply port 103 is coupled to an oxidizing gas supply manifold. Furthermore, the fuel gas discharge port 104 is coupled to a fuel gas discharge manifold; the coolant discharge port 105 is coupled to a coolant discharge manifold; and the oxidizing gas discharge port 106 is coupled to an oxidizing gas discharge manifold.

[0081] Fig. 8 shows the Fig. 7 shown fuel cell stack 100 in cross section along dotted line α. Furthermore, Fig. 9 is an expanded perspective exploded view of the fuel cell stack 100.

[0082] In the fuel cell stack 100, as shown in Fig. 8 and Fig. 9, the frame-integrated MEAs 120 and the separator pairs 140 are stacked one on top of the other. The separator pair 140 consists of metal separators (anode separator 130A and cathode separator 130B) that are adjacent to one another in the fuel cell stack 100.

[0083] Two separator pairs 140 clamping the MEA 120 integrated with the frame have the same structure as in Fig. 9. Furthermore, the frame-integrated MEA 120 consists of an MEA 121 and a frame 123 enclosing the outer periphery of the MEA 121. The MEA 121 further has a polymer electrolyte membrane 125 and a pair of catalyst electrodes 127 clamping the polymer electrolyte membrane 125 (see Fig. 12).

[0084] The frame 123 has a fuel gas supply manifold hole 110 for supplying fuel gas, a fuel gas discharge manifold hole 111 for discharging fuel gas, an oxidizing gas supply manifold hole 112 for supplying oxidizing gas, an oxidizing gas discharge manifold hole 113 for discharging oxidizing gas, a coolant supply manifold hole 114 for supplying coolant, and a coolant discharge manifold hole 115 for discharging coolant.

[0085] Fig. 10 shows a perspective exploded view of the Fig. 9 shown separator pair 140. The separator pair 140 is as in Fig. 10 by opposing the anode separator 130A and the cathode separator 130B such that their outer peripheral portions 133 are in contact with each other.

[0086] Each of the separators (130A and 130B) has a corrugated central portion 131, an outer peripheral portion 133 surrounding the central portion 131, and sealing elements provided on the outer peripheral portion 133.

[0087] The rear surface of the central portion 131 forms reaction gas channels 139, while the opposite surface of the central portion 131 forms coolant channels 141. Sections 132 for distributing reaction gas upstream and downstream of the reaction gas channels 139 are formed on the central portion 131, while sections 142 for distributing coolant upstream and downstream of the coolant channels 141 are formed. The rear surface of the central portion 131 is in contact with a catalyst electrode 127 of the MEA 121.

[0088] The outer peripheral portion 133 has a fuel gas supply manifold hole 110 for supplying fuel gas, a fuel gas discharge manifold hole 111 for discharging fuel gas, an oxidizing gas supply manifold hole 112 for supplying oxidizing gas, an oxidizing gas discharge manifold hole 113 for discharging oxidizing gas, a coolant supply manifold hole 114 for supplying coolant, and a coolant discharge manifold hole 115 for discharging coolant.

[0089] Three inlet grooves 135A and three outlet grooves 137A are formed on the opposite surface of the outer peripheral portion 133A of the anode separator 130A. The inlet grooves 135A communicate with the coolant supply manifold hole 114, not with the central portion 131A. The outlet grooves 137A further communicate with the coolant discharge manifold hole 115, not with the central portion 131A.

[0090] In this way, the inlet grooves 135A do not directly connect the coolant supply manifold hole 114 to the central portion 131A. The rear surface of the anode separator 130A therefore has a low area Y between the inlet grooves 135A and the central portion 131A. The inlet grooves 135A also do not directly connect the coolant discharge manifold hole 115 to the central portion 131A. The rear surface of the anode separator 130A therefore has a low area Y between the outlet grooves 137A and the central portion 131A.

[0091] Three inlet grooves 135B and three outlet grooves 137B are formed on the opposite surface of the outer peripheral portion 133B of the cathode separator 130B. The inlet grooves 135B communicate with the central portion 131B, not with the coolant supply manifold hole 114. Furthermore, the outlet grooves 137B communicate with the central portion 131B, not with the coolant discharge manifold hole 115.

[0092] In this way, the inlet grooves 135B do not directly connect the coolant supply manifold hole 114 to the central portion 131B. The rear surface of the cathode separator 130B therefore has a low area Y between the coolant supply manifold hole 114 and the inlet grooves 135B. The outlet grooves 137B also do not directly connect the coolant discharge manifold hole 115 to the central portion 131B. The rear surface of the cathode separator 130B therefore has a low area Y between the coolant discharge manifold hole 115 and the outlet grooves 137B.

[0093] The inlet grooves 135 and the outlet grooves 137 are preferably 0.8 to 2 mm wide and 0.25 to 0.5 mm deep, respectively. If the respective widths of the inlet grooves 135 and outlet grooves 137 were 2 mm or more, there would be a risk that the grooves would be compressed by clamping pressure, and the coolant inlet and outlet channels would be blocked. On the other hand, if the respective widths of the inlet grooves 135 and outlet grooves 137 were less than 0.8 mm or the depth of the grooves were less than 0.25 mm, there would be a risk that the pressure loss at the coolant inlet and outlet channels would be increased, so that a sufficient amount of coolant could not be supplied to the coolant channels.

[0094] The sealing elements include outer peripheral sealing elements 151 provided on the outer periphery of a separator; fuel gas sealing elements 153 enclosing the fuel gas supply manifold hole 110 and the fuel gas discharge manifold hole 111; oxidizing gas sealing elements 155 enclosing the oxidizing gas supply manifold hole 112 and the oxidizing gas discharge manifold hole 113; and coolant sealing elements 157 enclosing the coolant supply manifold hole 114 and the coolant discharge manifold hole 115.

[0095] The outer peripheral sealing elements 151 prevent the reaction gas or coolant from leaking out of the fuel cell stack. The fuel gas sealing elements 153 prevent the fuel gas from leaking out of the fuel gas passage manifold. The oxidizing gas sealing elements 155 prevent the oxidizing gas from leaking out of the oxidizing gas passage manifold. The coolant sealing elements 157 prevent the coolant from leaking out of the coolant passage manifold. Thus, the three fluids—fuel gas, oxidizing gas, and coolant—are never mixed with each other.

[0096] The dotted line in Fig. Figure 10 shows the sealing elements arranged on the rear surface of the cathode separator 130B shown. The sealing elements are as shown in Fig. 10, they are arranged only on the rear surfaces of the outer peripheral portions 133 of the separators 130, and not on the opposite surfaces of the outer peripheral portions 133. Furthermore, the outer peripheral portion 133A of the anode separator 130A and the outer peripheral portion 133B of the cathode separator 130B are in contact with each other. Thus, the outer peripheral portions 133 of the separators 130 are not twisted even when clamping pressure is applied.

[0097] Other features of the present invention, ie, the coolant inlet channels 143 and the coolant sealing elements 157, are explained below.

[0098] Fig. Figure 11 shows an expanded perspective view of an area near the coolant supply manifold hole 114 of the separator pair 140. Then Fig. 12 an expanded view of the fuel cell stack 100 in cross section along the line β in Fig. 11, and Fig. 13 an expanded view of the fuel cell stack 100 in cross section along the line γ in Fig. 11.

[0099] The separator pair 140 has, as in Fig. 12, the coolant passages 141, coolant distribution sections 142, and coolant inlet passages 143. The upper portions of the coolant inlet passages 143 consist of the inlet grooves 135A, and their lower portions consist of the inlet grooves 135B.

[0100] The inlet grooves 135A and 135B partially overlap. Such an overlap of the grooves 135A and 135B allows the coolant to flow from upstream to downstream. The width W of the area where the grooves 135A and 135B overlap is typically 1 to 2 mm.

[0101] The coolant sealing element 157A encloses, as in Fig. 12, the coolant supply manifold hole 114 and the inlet grooves 135A are arranged on the low surface Ya between the inlet grooves 135A and the central portion 131. The coolant sealing members 157B surround the coolant supply manifold hole 114 and are arranged on the low surface Yb ​​between the coolant supply manifold hole 114 and the inlet grooves 135B.

[0102] The coolant sealing member 157A thus overlaps an arrangement position of the inlet grooves 135B, and the coolant sealing members 157B overlap those of the inlet grooves 135A.

[0103] In this way, the coolant sealing elements 157 are arranged on the low surfaces Y, so that the thickness T1 of the separator pair 140 including the sealing portions can be made at least as thin as the sum of the thickness of metal sheets forming the separators and that of the two coolant sealing elements.

[0104] Furthermore, an area surrounded by the coolant sealing element 157A, as shown in Fig. 11 and Fig. 12, in plan view of the separator pair 140, the separator portion 140 is larger than that surrounded by the coolant sealing member 157B, and the coolant sealing member 157A and the coolant sealing members 157B do not overlap.

[0105] When the coolant sealing elements 157A and 157B do not overlap as described above, the thinnest region 122 of the frame 123 is only that which is sandwiched by the outer peripheral sealing elements 151A and 151B. On the other hand, when the coolant sealing elements 157A and 157B overlap, the region sandwiched by the outer peripheral sealing elements 151A and 151B and the region sandwiched by the outer peripheral sealing elements 157A and 157B are the thinnest, so the thinnest region 122 of the frame 123 is expanded (see FIG. Fig. 5).

[0106] The more extended the thinnest portion of the frame 123 is, the more reduced the strength of the frame 123 is, so that the thickness of the frame 123 must be increased accordingly.

[0107] On the other hand, if the thin portion of the frame 123 is limited as in the present invention, the strength of the frame 123 can be ensured without thickening it. Accordingly, the frame 123 can be made thinner than in the case of the extended thin portion of the frame 123.

[0108] The coolant discharge channels and the coolant sealing elements 157 are explained below.

[0109] Fig. Figure 14 shows an expanded perspective view of the separator pair 140 near the coolant discharge manifold hole 115. Furthermore, Fig. 15 an expanded view of the fuel cell stack 100 in cross section along the line β in Fig. 14, and Fig. 16 an expanded view of the fuel cell stack 100 in cross section along the line γ in Fig. 14.

[0110] The separator pair 140 has, as in Fig. 16, the coolant discharge channels 145 connect the coolant distribution sections 142 and the coolant supply distribution hole 114. The upper parts of the coolant discharge channels 145 consist of the outlet grooves 137B, and the lower parts consist of the outlet grooves 137A.

[0111] The outlet grooves 137B and 137A partially overlap. Such an overlap of the outlet grooves 137B and 137A allows the coolant to flow from upstream to downstream. The width W of the area where the outlet grooves 137B and 137A overlap is typically 1 to 2 mm.

[0112] The coolant sealing element 157A encloses, as in Fig.14 to 16, the coolant discharge manifold hole 115 and the outlet grooves 137A, and is arranged on the low surface Ya between the outlet grooves 137A and the central portion 131. The coolant sealing elements 157B surround the coolant discharge manifold hole 115 and are arranged on the low surface Yb ​​between the coolant discharge manifold hole 115 and the outlet grooves 137B.

[0113] Thus, the coolant sealing member 157A overlaps an arrangement position of the outlet grooves 137B, and the coolant sealing members 157B overlap those of the outlet grooves 137A.

[0114] The flow of fuel gas, oxidizing gas and coolant in such a fuel cell stack is explained below.

[0115] The fuel gas flowing from the fuel gas supply port 101 into the fuel gas supply manifold passes through the fuel gas channels 139A formed on the central portion 131 of the anode separator 130A; it then flows into the coolant discharge manifold before being discharged from the fuel gas discharge port 104. The fuel gas is supplied to the catalyst electrode of the MEA 121 by passing through the fuel gas channels 139A, thus contributing to power generation in fuel cells.

[0116] The fuel gas flowing from the oxidizing gas supply port 103 into the oxidizing gas supply manifold passes through the oxidizing gas channels 139B formed on the central portion 131B of the cathode separator 130B; it then flows into the coolant discharge manifold before being discharged from the oxidizing gas discharge port 106. The oxidizing gas is supplied to the catalyst electrode of the MEA 121 by passing through the oxidizing gas channels 139B, thus contributing to power generation in fuel cells.

[0117] The coolant flowing from the coolant supply port 102 into the coolant supply manifold passes through the coolant inlet channels 143 and then flows into the coolant channels. The coolant removes heat from the fuel cells as it passes through the coolant channels; it then flows into the coolant discharge manifold via the coolant discharge channels 145. Industrial applicability

[0118] The separator pair according to the invention, integrated with sealing elements, is highly reliably sealed, thus regulating the gas or coolant flow and reliably preventing mutual mixing. Furthermore, the fuel cell stack according to the invention is used in portable grid connections, electrical power supplies for motor vehicles, and combined heat and power systems for homes. List of reference symbols 100 fuel cell stacks 101 Fuel gas supply opening 102 Coolant supply opening 103 Oxidation gas supply opening 104 Fuel gas discharge opening 105 Coolant discharge opening 106 Oxidation gas discharge opening 107 End plate 108 fastening bolts 109 Mother 110 Fuel gas supply distribution hole 111 Fuel gas discharge distribution hole 112 Oxidation gas supply manifold hole 113 Oxidation gas discharge manifold hole 114 Coolant supply manifold hole 115 Coolant discharge manifold hole 120 frame-integrated MEA 121 MEA 122 thinnest section of the frame 123 frames 124 Deepening 125 polymer electrolyte membrane 127 Catalyst electrode 130 metal separators 131 central section 132 Section on reaction gas distribution 133 Outer circumference section 135 inlet groove 137 exhaust groove 139 Reaction gas channel 140 separator pair 141 Coolant channel 142 sections on coolant distribution 143 Coolant inlet channel 145 Coolant discharge channel 151 Outer peripheral sealing element 153 Fuel gas sealing element 155 Oxidation gas sealing element 157 Coolant sealing element

Claims

[1] Fuel cell stack (100) in which frame-integrated MEAs (120), each comprising an MEA (121) and a frame (123) enclosing the MEA (121) and having a coolant supply distribution hole (114), and Separator pairs (140), each comprising an anode separator (130A) and a cathode separator (130B), each having a corrugated central portion (131) forming channels and an outer peripheral portion (133) surrounding the central portion (131), positioned opposite one another in such a way as to bring the outer peripheral portions (133) into contact with one another, wherein the anode separator (130A) and the cathode separator (130B) have a coolant supply distribution hole (114) arranged on the outer peripheral portion (133) and coolant sealing elements (157) arranged on the back of the contact area of ​​the outer peripheral portion (133), are stacked on top of each other, with the frame (123) has recesses (124) receiving the coolant sealing elements (157), the separator pair (140) comprises coolant channels (141) consisting of opposite surfaces of the central portions (131) of the anode separator (130A) and the cathode separator (130B) and a coolant inlet channel (143) connecting the coolant channels (141) and the coolant supply distribution hole (114), an upper part of the coolant inlet channel (143) consists of an inlet groove (135A) formed on an opposite surface (133A) of the outer peripheral portion (133) of the anode separator (130A) and communicating with the coolant supply distribution hole (114), a lower part of the coolant inlet channel (143) consists of an inlet groove (135B) formed on an opposite surface of the outer peripheral portion (133B) of the cathode separator (130B) and communicating with the central portion (131), a coolant sealing member (157A) arranged on the back of the contact area of ​​the outer peripheral portion (133A) of the anode separator (130A), the coolant supply distribution hole (114) and the groove (135A) and a coolant sealing element (157B) arranged on the back of the contact area of ​​the outer peripheral portion (133B) of the cathode separator (130B) encloses the coolant supply distribution hole (114), wherein the inlet groove (135A) of the anode separator (130A) does not directly connect the coolant supply distribution hole (114) to the central portion (131A), and wherein the inlet groove (135B) of the cathode separator (130B) does not directly connect the coolant supply distribution hole (114) to the central portion (131B), wherein, when the frame-integrated MEAs (120) and the separator pairs (140) are stacked on top of each other, the inlet groove (135A) of the anode separator (130A) and the inlet groove (135B) of the cathode separator (130B) partially overlap. [2] The fuel cell stack according to claim 1, wherein the area surrounded by the coolant sealing member (157A) includes that surrounded by the coolant sealing member (157B), and the coolant sealing member (157A) and the coolant sealing member (157B) do not overlap. [3] The fuel cell stack according to claim 1, wherein the outer peripheral portion (133) further comprises a coolant discharge manifold hole (115), wherein the separator pair (140) further comprises a coolant discharge channel (145) connecting the coolant channels (141) and the coolant discharge distribution hole (115), an upper part of the coolant inlet channel (143) consists of an outlet groove (137B) formed on the opposite surface of the outer peripheral portion (133B) of the cathode separator (130B) and communicating with the central portion (131), and a lower part of the coolant inlet channel (143) consists of an outlet groove (137A) formed on the opposite surface of the outer peripheral portion (133A) of the anode separator (130A) and communicating with the anode separator (130A) and the cathode separator (130B).

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