Fuel Cell Stack

Abstract

To provide a fuel cell stack capable of extending service life with an inexpensive configuration.SOLUTION: With a fuel cell stack, at least one separator of a cathode separator and an anode separator in at least one unit cell of a plurality of unit cells includes, in a region adjacent to a cooling liquid manifold of the unit cell in a surface direction, a sacrificial electrolytic corrosion region that is not bonded to an insulation sheet adjacent in a stacking direction and a seal region adjacent to the sacrificial electrolytic corrosion region in the surface direction and bonded to the insulation sheet. In the sacrificial electrolytic corrosion region, a cooling liquid lead-in / out region of the separator is tabular in contact with the insulation sheet. A region other than the cooling liquid lead-in / out region in the sacrificial electrolytic corrosion region has an uneven shape at least partially not in contact with the insulation sheet.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a fuel cell stack. [Background technology]

[0002] Various research projects are being conducted on fuel cells. For example, Patent Document 1 discloses a technique for dealing with electrolytic corrosion occurring in a cooling water manifold by separately providing a sacrificial member. For example, Patent Document 2 discloses a fuel cell stack that can suppress the occurrence of corrosion in separators. For example, Patent Document 3 discloses a fuel cell system that effectively prevents corrosion of the separator, etc., particularly on the high potential side. For example, Patent Document 4 discloses a fuel cell equipped with a mechanism for preventing corrosion of the separator plates caused by cooling water that recovers heat from the fuel cell. For example, Patent Document 5 discloses a fuel cell equipped with a mechanism for preventing corrosion of fuel cell stack components, such as conductive separators, caused by a coolant that recovers heat from the fuel cell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4901169 [Patent Document 2] JP 2016-096033 A [Patent Document 3] JP 2008-016216 A [Patent Document 4] JP 2010-113864 A [Patent Document 5] JP 2010-113863 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the coolant inlet / outlet area of ​​the coolant manifold of the fuel cell stack, high temperature coolant flows out, particularly on the outlet side, which increases the ionic conductivity of the coolant, reduces the ionic resistance of the coolant, concentrates electrolytic corrosion, and shortens the lifespan of the fuel cell stack. In the prior art, a sacrificial member is separately provided to counter electrolytic corrosion occurring in the coolant manifold, and this countermeasure increases the number of parts constituting the fuel cell stack, raising the cost of the fuel cell stack. In addition, in order to prevent electrolytic corrosion from occurring in the coolant manifold, if the separator substrate of the cell where electrolytic corrosion occurs is changed from an inexpensive stainless steel material such as SUS to a highly corrosion-resistant material such as Ti, the cost of the fuel cell stack will increase.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and has as its main object to provide a fuel cell stack that has an inexpensive configuration and a long lifespan. [Means for solving the problem]

[0006] In the present disclosure, there is provided a fuel cell stack having a cell stack in which a plurality of unit cells each having a stainless steel separator are stacked, The single cell includes a cathode separator, an anode separator, and an insulating sheet disposed between the cathode separator and the anode separator; In at least one of the plurality of unit cells, at least one of the cathode separator and the anode separator has, in a region adjacent to a coolant manifold of the unit cell in a surface direction, a sacrificial corrosion region that is not bonded to the insulating sheet adjacent in the stacking direction, and a seal region that is adjacent to the sacrificial corrosion region in the surface direction and bonded to the insulating sheet, A fuel cell stack is provided in which, in the sacrificial electrolytic corrosion region, the shape of the coolant discharge inlet / outlet region of the separator is flat and in contact with the insulating sheet, and the shape of the region in the sacrificial electrolytic corrosion region other than the coolant discharge inlet / outlet region is uneven and at least partially does not contact the insulating sheet.

[0007] In the fuel cell stack of the present disclosure, when the width in the surface direction from the end of the coolant inlet / outlet side of the coolant manifold of the sacrificial corrosion area is defined as a sacrificial corrosion distance W (mm), the product of the sacrificial corrosion distance W (mm) and the thickness D (mm) of the separator is a sacrificial corrosion area W×D of 0.25 mm 2 It may be more than that.

[0008] In the fuel cell stack of the present disclosure, at least one separator selected from the group consisting of a cathode separator of a highest potential single cell among the multiple single cells, which contributes to power generation and has the highest electrical potential, a cathode separator of an end single cell adjacent to the highest potential single cell and which does not contribute to power generation, and an anode separator of the end single cell, may have a sacrificial corrosion area protruding portion that protrudes in the planar direction in a portion of the coolant manifold beyond the insulating sheet adjacent to the separator.

[0009] In the fuel cell stack of the present disclosure, the cathode separator of the highest potential unit cell may have the sacrificial electrolytic corrosion region protrusion.

[0010] In the fuel cell stack of the present disclosure, the sacrificial corrosion distance W (mm) is 2.1 to 13 mm, The separator may have a thickness D (mm) of 0.08 to 0.12 mm. Effect of the Invention

[0011] The fuel cell stack of the present disclosure can be constructed inexpensively and have a long lifespan. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the vicinity of a coolant discharge manifold of a fuel cell stack according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing an example for illustrating a sacrificial electrolytic corrosion distance W and a separator thickness D in the vicinity of a coolant discharge manifold of a fuel cell stack according to a second embodiment of the present disclosure. [Diagram 3] FIG. 3 is a graph showing an example of the relationship between the sacrificial electrolytic corrosion distance W of separators having different ionic conductivities in a fuel cell stack according to a second embodiment of the present disclosure and the lifespan of the fuel cell stack. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of the vicinity of a coolant discharge manifold of a fuel cell stack according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described. Note that matters other than those specifically mentioned in this specification and necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of a fuel cell stack that do not characterize the present disclosure) can be understood as design matters of a person skilled in the art based on the prior art in the field. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the field. Furthermore, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships. In this specification, the use of "to" indicating a numerical range means that the numerical values ​​before and after it are included as the lower limit and upper limit. Furthermore, any combination of upper and lower limits in a numerical range can be used.

[0014] In the present disclosure, there is provided a fuel cell stack having a cell stack in which a plurality of unit cells each having a stainless steel separator are stacked, The single cell includes a cathode separator, an anode separator, and an insulating sheet disposed between the cathode separator and the anode separator; In at least one of the plurality of unit cells, at least one of the cathode separator and the anode separator has, in a region adjacent to a coolant manifold of the unit cell in a surface direction, a sacrificial corrosion region that is not bonded to the insulating sheet adjacent in the stacking direction, and a seal region that is adjacent to the sacrificial corrosion region in the surface direction and bonded to the insulating sheet, A fuel cell stack is provided in which, in the sacrificial electrolytic corrosion region, the shape of the coolant discharge inlet / outlet region of the separator is flat and in contact with the insulating sheet, and the shape of the region in the sacrificial electrolytic corrosion region other than the coolant discharge inlet / outlet region is uneven and at least partially does not contact the insulating sheet.

[0015] In the present disclosure, in a cell where electrolytic corrosion occurs, a predetermined region from the end of the coolant manifold is designated as a sacrificial electrolytic corrosion region using inexpensive stainless steel material, and a seal structure is set outside of this region. In the present disclosure, a coolant manifold for a fuel cell using a stainless steel separator has a sacrificial electrolytic corrosion region, and in the coolant lead-in / out region of the sacrificial electrolytic corrosion region, the separator is flat and only one side is in contact with the coolant, while the portion of the sacrificial electrolytic corrosion region other than the coolant lead-in / out region has an uneven shape and includes an area that does not contact an insulating sheet, and has a structure in which both sides of the separator are in contact with the coolant during electrolytic corrosion. By increasing the area by providing surface unevenness, the sacrificial electrolytic corrosion region functions more as a sacrificial material. According to the present disclosure, in the area of ​​the sacrificial corrosion area that is not in contact with the insulating sheet, electrolytic corrosion occurs on both sides of the separator, promoting the electrolytic reaction. Therefore, the effect of sacrificial electrolytic corrosion in the relevant area is increased, electrolytic corrosion concentration in the coolant inlet / outlet area is mitigated, and the life of the fuel cell stack can be extended. In addition, the use of stainless steel separators allows for an inexpensive configuration.

[0016] The fuel cell stack of the present disclosure has a cell stack in which a plurality of unit cells each having a stainless steel separator are stacked. In this disclosure, both a single cell and a fuel cell stack in which single cells are stacked may be referred to as a fuel cell. In this disclosure, a single cell may be referred to as a cell.

[0017] The cell stack is a stack of a plurality of unit cells. The number of stacked unit cells in the cell stack is not particularly limited, and may be from 2 to several hundred. A fastening load may be applied to the cell stack by a fastening member. The fastening member may be a shaft member such as a bolt with threads on both ends and a nut, or a spring member. The fuel cell stack may have a pair of end plates on both ends of the cell stack in the stacking direction. Methods for fastening the cell stack include a method of applying a fastening load by screwing using shaft members such as threaded bolts and nuts on both ends of a pair of end plates arranged at both ends of the cell stack in the stacking direction, and a method of applying a fastening load using a spring member.

[0018] A single cell of a fuel cell comprises a cathode separator, an anode separator, and an insulating sheet disposed between the cathode separator and the anode separator, and typically comprises a membrane electrode gas diffusion layer assembly (MEGA). The membrane electrode gas diffusion layer assembly has, in this order, an anode gas diffusion layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, and a cathode gas diffusion layer.

[0019] The cathode (oxidant electrode) includes a cathode catalyst layer and a cathode-side gas diffusion layer. The anode (fuel electrode) includes an anode catalyst layer and an anode-side gas diffusion layer. The cathode catalyst layer and the anode catalyst layer are collectively referred to as catalyst layers. The catalyst layer may include, for example, a catalytic metal that promotes an electrochemical reaction, an electrolyte having proton conductivity, and a carrier having electron conductivity. As the catalytic metal, for example, platinum (Pt) and alloys of Pt and other metals (for example, Pt alloys mixed with cobalt and nickel, etc.) can be used. The electrolyte may be a fluorine-based resin, etc. As the fluorine-based resin, for example, a Nafion solution, etc. may be used. The catalytic metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalytic metal (catalyst-supporting carrier) and the electrolyte may be mixed. The support for supporting the catalytic metal may be, for example, a carbon material such as carbon that is generally available commercially.

[0020] The cathode side gas diffusion layer and the anode side gas diffusion layer are collectively referred to as a gas diffusion layer. The gas diffusion layer may be a gas-permeable conductive member or the like. Examples of the conductive member include porous carbon materials such as carbon cloth and carbon paper, and porous metal materials such as metal mesh and foamed metal.

[0021] The electrolyte membrane may be a solid polymer electrolyte membrane. Examples of the solid polymer electrolyte membrane include a fluorine-based electrolyte membrane such as a thin film of perfluorosulfonic acid containing water, and a hydrocarbon-based electrolyte membrane. The electrolyte membrane may be, for example, a Nafion membrane (manufactured by DuPont).

[0022] The insulating sheet is disposed between the cathode separator and the anode separator, and may be disposed around the outer periphery of the membrane electrode gas diffusion layer assembly. The insulating sheet may have a framework, openings, and holes. The framework is the main part of the insulating sheet that connects to the membrane electrode gas diffusion layer assembly. The opening is a holding region for the membrane electrode gas diffusion layer assembly, and is a region penetrating a part of the skeleton to accommodate the membrane electrode gas diffusion layer assembly. The opening may be located at a position in the insulating sheet where the skeleton is disposed around (outer periphery of) the membrane electrode gas diffusion layer assembly, and may be located in the center of the insulating sheet. The holes in the insulating sheet allow fluids such as reactant gases and coolants to flow in the stacking direction of the unit cells. The holes in the insulating sheet may be aligned and arranged to communicate with the holes in the separators. The insulating sheet may include a frame-shaped core layer and two frame-shaped shell layers, that is, a first shell layer and a second shell layer, provided on both sides of the core layer. The first shell layer and the second shell layer may be provided in a frame shape on both sides of the core layer, similarly to the core layer.

[0023] The core layer may be a structural member having gas sealing and insulating properties, and may be formed of a material whose structure does not change even under the temperature conditions during thermocompression bonding in the manufacturing process of the fuel cell. Specifically, the material of the core layer may be, for example, polyethylene, polypropylene, PC (polycarbonate), PPS (polyphenylene sulfide), PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PA (polyamide), PI (polyimide), PS (polystyrene), PPE (polyphenylene ether), PEEK (polyether ether ketone), cycloolefin, PES (polyethersulfone), PPSU (polyphenylsulfone), LCP (liquid crystal polymer), epoxy resin, or other resin. The material of the core layer may be a rubber material such as EPDM (ethylene propylene diene rubber), fluorine-based rubber, or silicon-based rubber. The thickness of the core layer may be 5 μm or more, or may be 20 μm or more, from the viewpoint of ensuring insulation, and may be 200 μm or less, or may be 150 μm or less, from the viewpoint of reducing the cell thickness.

[0024] The first and second shell layers may have properties such as high adhesiveness to other substances, softening under temperature conditions during thermocompression bonding, and a lower viscosity and melting point than the core layer in order to bond the core layer to the anode separator and the cathode separator and ensure sealing properties. Specifically, the first and second shell layers may be thermoplastic resins such as polyester and modified olefin, or may be thermosetting resins such as modified epoxy resin. The resin constituting the first shell layer and the resin constituting the second shell layer may be the same type of resin or different types of resin. By providing shell layers on both sides of the core layer, adhesion between the insulating sheet and the two separators by hot pressing becomes easier. The thickness of each of the first shell layer and the second shell layer may be 5 μm or more, or 30 μm or more, from the viewpoint of ensuring adhesion, and may be 100 μm or less, or 40 μm or less, from the viewpoint of reducing the cell thickness.

[0025] In the insulating sheet, the first shell layer and the second shell layer may be provided only in the portions that are bonded to the anode separator and the cathode separator, respectively (separator seal areas). The first shell layer provided on one surface of the core layer may be bonded to the cathode separator. The second shell layer provided on the other surface of the core layer may be bonded to the anode separator. The insulating sheet may be sandwiched between a pair of separators.

[0026] The fuel cell stack may have manifolds with the holes communicating with each other, such as a supply manifold with the supply holes communicating with each other, and a discharge manifold with the discharge holes communicating with each other. The supply manifold may include a fuel gas supply manifold, an oxidant gas supply manifold, and a coolant supply manifold. Examples of the exhaust manifold include a fuel gas exhaust manifold, an oxidant gas exhaust manifold, and a coolant exhaust manifold. In this disclosure, the coolant supply manifold and the coolant exhaust manifold are collectively referred to as the coolant manifold.

[0027] The fuel cell stack may include a gasket between adjacent unit cells, which is used as a seal to prevent leakage of reaction gas from each reaction gas system. The gasket may be ethylene propylene diene rubber (EPDM) rubber, silicone rubber, thermoplastic elastomer resin, or the like.

[0028] The single cell includes a pair of separators. The pair of separators sandwich an insulating sheet, and usually also sandwich a membrane electrode gas diffusion layer assembly. One of the pair of separators is an anode separator and the other is a cathode separator In the present disclosure, the anode separator and the cathode separator are collectively referred to as separators. The separator may have holes such as supply holes and exhaust holes for passing fluids such as reactant gases and coolant in the stacking direction of the unit cells. As the coolant, for example, a mixed solution of ethylene glycol and water can be used to prevent freezing at low temperatures. Examples of the supply hole include a fuel gas supply hole, an oxidant gas supply hole, and a coolant supply hole. Examples of the exhaust hole include a fuel gas exhaust hole, an oxidant gas exhaust hole, and a coolant exhaust hole. In this disclosure, these holes may be conveniently referred to as manifolds. The separator may have a reactant gas flow path on the surface in contact with the gas diffusion layer, and may have a coolant flow path on the surface opposite to the surface in contact with the gas diffusion layer to maintain a constant temperature of the fuel cell. The anode separator may have a fuel gas flow path on the surface in contact with the anode-side gas diffusion layer, and may have a coolant flow path on the surface opposite to the surface in contact with the anode-side gas diffusion layer for maintaining a constant temperature of the fuel cell. The cathode separator may have an oxidant gas flow path on the surface in contact with the cathode-side gas diffusion layer, and may have a coolant flow path on the surface opposite to the surface in contact with the cathode-side gas diffusion layer for maintaining a constant temperature of the fuel cell. The separator may be a plate made of stainless steel such as SUS. The shape of the separator may be rectangular, horizontally elongated hexagonal, horizontally elongated octagonal, circular, oval, or the like.

[0029] In this disclosure, the fuel gas and the oxidant gas are collectively referred to as reactant gases. The reactant gas supplied to the anode is the fuel gas, and the reactant gas supplied to the cathode is the oxidant gas. The fuel gas is a gas that mainly contains hydrogen, and may be hydrogen. The oxidant gas is a gas that contains oxygen, and may be oxygen, air, dry air, etc.

[0030] The separator has a coolant inlet / outlet region between the coolant flow passage and a coolant supply hole or coolant discharge hole that constitutes the coolant manifold. Specifically, the separator has a coolant inlet region between the coolant supply hole that constitutes the coolant supply manifold and the coolant flow path, and has a coolant outlet region between the coolant discharge hole that constitutes the coolant discharge manifold and the coolant flow path. The coolant inlet / outlet region means a coolant inlet region or a coolant outlet region. The area of ​​the separator adjacent in the surface direction to the coolant manifold (the coolant supply hole or the coolant discharge hole constituting the coolant manifold) of the unit cell has a coolant inlet / outlet area and an area other than the coolant inlet / outlet area. Specifically, the region of the separator adjacent to the coolant supply manifold of the single cell in the surface direction has a coolant inlet region and a region other than the coolant inlet region, and the region of the separator adjacent to the coolant discharge manifold of the single cell in the surface direction has a coolant outlet region and a region other than the coolant outlet region. The region other than the coolant lead-in / out region may be a region adjacent to the coolant supply manifold of the single cell in the surface direction of the separator, and may be a region not communicating with the coolant flow path.

[0031] (1) First embodiment In at least one of the multiple unit cells of the fuel cell stack of the first embodiment of the present disclosure, at least one of the cathode separator and the anode separator has, in a region adjacent to the coolant manifold of the unit cell in a face direction, a sacrificial corrosion region that is not bonded to an insulating sheet adjacent in the stacking direction, and a seal region that is adjacent to the sacrificial corrosion region in the face direction and bonded to the insulating sheet. That is, the sacrificial electrolytic corrosion region is a region of the separator that is adjacent to the coolant manifold in the surface direction and is not bonded to the insulating sheet. The seal region is a region of the separator that is adjacent to the sacrificial electrolytic corrosion region in the surface direction and is also a region that is bonded to the insulating sheet. The sacrificial electrolytic corrosion region may be provided in at least one of the cathode separator and the anode separator, and may be provided in both separators. The sacrificial electrolytic corrosion region needs to be provided in at least one unit cell among the plurality of unit cells, and may be provided in all unit cells.

[0032] In the sacrificial electrolytic corrosion region, the shape of the coolant inlet / outlet region of the separator is a flat plate in contact with the insulating sheet. The shape of the sacrificial electrolytic corrosion region of the separator other than the coolant inlet / outlet region may be irregular so long as it is at least partially not in contact with the insulating sheet, and it does not have to be entirely in contact with the insulating sheet as long as it is irregular. In the sacrificial electrolytic corrosion region, the shape of the coolant introduction region of the separator is flat and in contact with the insulating sheet, and the shape of the region in the sacrificial electrolytic corrosion region other than the coolant introduction region may be uneven and at least partially not in contact with the insulating sheet. In the sacrificial electrolytic corrosion region, the shape of the coolant discharge region of the separator is flat and in contact with the insulating sheet, and the shape of the region in the sacrificial electrolytic corrosion region other than the coolant discharge region may be uneven and at least partially not in contact with the insulating sheet.

[0033] FIG. 1 is a schematic cross-sectional view showing an example of the vicinity of a coolant discharge manifold of a fuel cell stack according to a first embodiment of the present disclosure. As shown in FIG. 1, in the fuel cell stack of the first embodiment of the present disclosure, in each unit cell, the cathode separator and the anode separator have, in an area adjacent in a face direction to the coolant discharge manifold of the unit cell, a sacrificial corrosion area that is not bonded to the insulating sheet adjacent in the stacking direction, and a seal area that is adjacent in a face direction to the sacrificial corrosion area and bonded to the insulating sheet. In the sacrificial electrolytic corrosion region, the shape of the coolant discharge region of the separator is flat and in contact with the insulating sheet, and the shape of the region other than the coolant discharge region in the sacrificial electrolytic corrosion region is uneven and partially not in contact with the sheet. Although FIG. 1 shows an example of a coolant discharge manifold as the coolant manifold, the coolant manifold may be configured in the same manner as the coolant discharge manifold even when the coolant manifold is a coolant supply manifold.

[0034] (2) Second embodiment In the fuel cell stack according to the second embodiment of the present disclosure, when the width in the planar direction from the end of the coolant inlet / outlet side of the coolant manifold of the sacrificial corrosion area is defined as the sacrificial corrosion distance W (mm), the product of the sacrificial corrosion distance W (mm) and the thickness D (mm) of the separator is 0.25 mm 2 From the viewpoint of the balance between the size (energy density) and life of the fuel cell stack, the upper limit is 1.00 mm 2 It may be the following. The sacrificial corrosion distance W (mm) may be 2.1 to 13 mm, with the lower limit being 2.5 mm or more, or 3 mm or more, and the upper limit being 6 mm or less, or 4 mm or less. The thickness D (mm) of the separator may be 0.08 to 0.12 mm, and the lower limit may be 0.1 mm or more. The ionic conductivity of the separator is not particularly limited and is 1 to 8 μS / cm 2 may be 2 to 6 μS / cm 2 may be also possible. The end of the sacrificial electrolytic corrosion region on the coolant inlet / outlet side of the coolant manifold may be the end of the coolant lead-in / out area of ​​the separator on the coolant manifold side. The end of the sacrificial electrolytic corrosion region on the coolant inlet side of the coolant supply manifold may be the end of the coolant introduction region of the separator on the coolant supply manifold side. The end of the sacrificial electrolytic corrosion region on the coolant outlet side of the coolant discharge manifold may be the end of the coolant discharge manifold side of the coolant lead-out region of the separator.

[0035] FIG. 2 is a schematic cross-sectional view showing an example for illustrating a sacrificial electrolytic corrosion distance W and a separator thickness D in the vicinity of a coolant discharge manifold of a fuel cell stack according to a second embodiment of the present disclosure. Although FIG. 2 shows an example of a coolant discharge manifold as the coolant manifold, the coolant manifold may be configured in the same manner as the coolant discharge manifold even when the coolant manifold is a coolant supply manifold.

[0036] FIG. 3 is a graph showing an example of the relationship between the sacrificial electrolytic corrosion distance W of separators having different ionic conductivities in a fuel cell stack according to a second embodiment of the present disclosure and the lifespan of the fuel cell stack. The life of a fuel cell stack is determined by, for example, the sacrificial corrosion volume V (mm 3 ) and the separator's electrolytic corrosion rate S (mol / s) and the separator's ionic conductivity (μS / cm 2 ) may be estimated based on empirical rules. In this disclosure, the sacrificial corrosion volume V (mm 3 ) is the product D x W x L of the separator thickness D (mm), the sacrificial corrosion distance W (mm), which is the width in the planar direction from the end of the coolant inlet / outlet of the coolant manifold, and the coolant manifold circumference L (mm). In this disclosure, the electrolytic corrosion rate S (mol / s) of the separator is calculated by the perimeter L (mm) of the coolant manifold, the length d (mm) of the electrolytic reaction region of the separator, and the reaction rate v (mol / s mm 2 ) is the product L×d×v.

[0037] According to the second embodiment of the present disclosure, the electrolytic corrosion of the separator in the coolant manifold is limited to the sacrificial electrolytic corrosion area, so that the seal structure of the unit cell is not destroyed even after the separator dissolves in the sacrificial electrolytic corrosion area, and the seal function of the unit cell can be protected, thereby extending the life of the fuel cell stack. Furthermore, by keeping the sacrificial electrolytic corrosion area below a predetermined value, a good balance between the life span and the energy density of the fuel cell stack can be achieved.

[0038] (3) Third embodiment In a fuel cell stack of a third embodiment of the present disclosure, at least one separator selected from the group consisting of a cathode separator of a highest potential single cell that contributes to power generation and has the highest electrical potential among a plurality of single cells, a cathode separator of an end single cell adjacent to the highest potential single cell and not contributing to power generation, and an anode separator of the end single cell may have a sacrificial corrosion area protruding portion that protrudes in the planar direction in a portion of the coolant manifold beyond the insulating sheet adjacent to the separator. In the fuel cell stack of the third embodiment of the present disclosure, at least the cathode separator of the highest potential unit cell may have a sacrificial corrosion area protrusion, and further, the cathode separator of an end unit cell adjacent to the highest potential unit cell and not contributing to power generation, and the anode separator of the end unit cell may have a sacrificial corrosion area protrusion. The sacrificial corrosion area protrusion may protrude in the planar direction beyond the insulating sheet onto a portion of the coolant supply manifold, may protrude in the planar direction onto a portion of the coolant discharge manifold, or may protrude in the planar direction onto a portion of the coolant supply manifold and a portion of the coolant discharge manifold. The sacrificial electrolytic corrosion region protrusion may protrude in the planar direction beyond the insulating sheet to a portion of the coolant manifold, and may protrude in a manner not to block the coolant manifold.

[0039] FIG. 4 is a schematic cross-sectional view showing an example of the vicinity of a coolant discharge manifold of a fuel cell stack according to a third embodiment of the present disclosure. As shown in FIG. 4, in a fuel cell stack according to a third embodiment of the present disclosure, the cathode separator of the highest potential single cell, which contributes to power generation among the multiple single cells and has the highest electrical potential, has a sacrificial corrosion region protruding portion that protrudes in the planar direction into a portion of the coolant discharge manifold beyond the insulating sheet adjacent to the cathode separator. Although FIG. 4 shows an example of a coolant discharge manifold as the coolant manifold, the coolant manifold may be configured in the same manner as the coolant discharge manifold even when the coolant manifold is a coolant supply manifold.

[0040] In a third embodiment of the present disclosure, among the separators of the stacked power generation cells, only the cathode separator, which has the highest potential and is closest to the negative side, or the separator of the end cell adjacent thereto, is made to protrude toward the coolant manifold side beyond the adjacent insulating sheet. As a result, the protruding edge of the separator is electrolytically corroded and acts as a sacrificial electrode, protecting the other members. In addition, since there are one to three separators protruding from the insulating sheet, there is no risk of contact with other separators with different potentials, which could lead to insulation breakdown.

Claims

1. A fuel cell stack having a cell stack in which a plurality of unit cells each having a stainless steel separator are stacked, The single cell includes a cathode separator, an anode separator, and an insulating sheet disposed between the cathode separator and the anode separator; In at least one of the plurality of unit cells, at least one of the cathode separator and the anode separator has, in a region adjacent to a coolant manifold of the unit cell in a surface direction, a sacrificial corrosion region that is not bonded to the insulating sheet adjacent in the stacking direction, and a seal region that is adjacent to the sacrificial corrosion region in the surface direction and bonded to the insulating sheet, A fuel cell stack, in which, in the sacrificial electro-corrosion region, the shape of the coolant discharge inlet / outlet region of the separator is flat and in contact with the insulating sheet, and the shape of the region in the sacrificial electro-corrosion region other than the coolant discharge inlet / outlet region is uneven and at least partially does not contact the insulating sheet.

2. When the width of the sacrificial corrosion area in the surface direction from the end of the coolant inlet / outlet side of the coolant manifold is defined as a sacrificial corrosion distance W (mm), the product of the sacrificial corrosion distance W (mm) and the thickness D (mm) of the separator, that is, a sacrificial corrosion area W×D, is 0.25 mm ２ The fuel cell stack according to claim 1 .

3. 2. The fuel cell stack according to claim 1, wherein at least one separator selected from the group consisting of a cathode separator of a highest potential unit cell that contributes to power generation and has the highest electrical potential among the plurality of unit cells, a cathode separator of an end unit cell adjacent to the highest potential unit cell and not contributing to power generation, and an anode separator of the end unit cell has a sacrificial electrolytic corrosion region protruding portion that protrudes in a planar direction in a portion of an area of ​​the coolant manifold beyond the insulating sheet adjacent to the separator.

4. 4. The fuel cell stack of claim 3, wherein the cathode separator of the highest potential single cell has the sacrificial corrosion area protrusion.

5. The sacrificial corrosion distance W (mm) is 2.1 to 13 mm, 3. The fuel cell stack according to claim 2, wherein the separator has a thickness D (mm) of 0.08 to 0.12 mm.

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