JP2023135769A - fuel cell stack - Google Patents

Abstract

To provide a fuel cell stack capable of suppressing mixing of a fuel gas into a coolant passage.SOLUTION: Provided is a fuel cell stack that has a cell laminate configured by laminating a plurality of single cells each comprising a cathode separator and an anode separator, using a seal sheet for a seal between adjacent single cells. The fuel cell stack has a fuel gas manifold. The seal sheet has a double-seal structure of a first seal line that surrounds and seals the fuel gas manifold in a plan view and a second seal line that surrounds the first seal line. A rib of the cathode separator in contact with the second seal line is provided with a penetration hole that allows an oxidant gas to be supplied from an oxidant gas passage of the cathode separator to a double-seal interspace part between the first seal line and the second seal line and that penetrates through the rib in a plane direction. The double-seal interspace part has a structure that can be filled with the oxidant gas by means of the penetration hole.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to fuel cell stacks.

Various studies have been conducted regarding fuel cells.
For example, Patent Document 1 discloses a technique that can reduce or eliminate side flow through the outer circumferential portion of a metal spring seal by inserting a filler into the outer circumferential seal portion.
Patent Document 2 discloses a fuel cell that makes it possible to reliably prevent fuel gas flowing through a fuel gas communication hole from entering a coolant flow path.
Patent Document 3 discloses a fuel cell stack in which at least one of the support frame and the separator is provided with a through hole between the first and second bead seal parts.

Special table 2017-535915 publication JP2008-277184A Japanese Patent Application Publication No. 2020-149804

Conventional fuel cell stacks have a structure in which the fuel gas manifold seal part goes inside the outer seal in order to realize a low-cost cell seal structure at the outer circumference using a sheet-shaped sealing material (seal sheet). Become. At that time, there is a problem in that the fuel gas is in contact with the refrigerant flow path across the fuel gas manifold seal line, and the fuel gas mixes into the refrigerant flow path.

The present disclosure has been made in view of the above circumstances, and its main purpose is to provide a fuel cell stack that can suppress the mixing of fuel gas into a refrigerant flow path.

In the present disclosure, a fuel cell stack has a cell stack in which a plurality of unit cells each having a cathode separator and an anode separator are stacked, and a seal sheet is used for sealing between adjacent unit cells,
The fuel cell stack has a fuel gas manifold,
The seal sheet has a double seal structure including a first seal line that surrounds and seals the fuel gas manifold in a plan view, and a second seal line that surrounds the first seal line,
The rib of the cathode separator in contact with the second seal line is provided with an oxidant gas from the oxidant gas flow path of the cathode separator to the space between the double seals between the first seal line and the second seal line. A through hole is provided that penetrates the rib in a planar direction, and is capable of supplying
The space between the double seals provides a fuel cell stack having a structure that can be filled with the oxidizing gas through the through hole.

The fuel cell stack of the present disclosure can suppress mixing of fuel gas into the refrigerant flow path.

In FIG. 1, the upper figure is a schematic plan view showing an example of the vicinity of the fuel gas manifold of the fuel cell stack of the present disclosure when viewed from above, and the lower figure is a schematic cross-sectional view taken along line AA.

Embodiments according to the present disclosure will be described below. Note that matters other than those specifically mentioned in this specification that are 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) are It can be understood as a matter of design by a person skilled in the art based on the prior art in the field. The present disclosure can be implemented based on the content disclosed in this specification and the common general knowledge in the field.
Furthermore, the dimensional relationships (length, width, thickness, etc.) in the figures do not reflect the actual dimensional relationships.
In this specification, "~" indicating a numerical range is used to include the numerical values written before and after it as the lower limit and upper limit.
Furthermore, any combination of upper and lower limits in the numerical range can be adopted.

In the present disclosure, a fuel cell stack has a cell stack in which a plurality of unit cells each having a cathode separator and an anode separator are stacked, and a seal sheet is used for sealing between adjacent unit cells,
The fuel cell stack has a fuel gas manifold,
The seal sheet has a double seal structure including a first seal line that surrounds and seals the fuel gas manifold in a plan view, and a second seal line that surrounds the first seal line,
The rib of the cathode separator in contact with the second seal line is provided with an oxidant gas from the oxidant gas flow path of the cathode separator to the space between the double seals between the first seal line and the second seal line. A through hole is provided that penetrates the rib in a planar direction, and is capable of supplying
The space between the double seals provides a fuel cell stack having a structure that can be filled with the oxidizing gas through the through hole.

In the present disclosure, the fuel gas manifold has a double seal structure, and the space between the double seals is filled with oxidizing gas (air). In order to fill the space between the double seals with oxidizing gas, the ribs of the separator under the outer seal of the double seal structure are provided with oxidizing gas from the oxidizing gas flow path of the cathode separator to the space between the double seals. It is characterized by having a through hole through which it is possible to supply.
According to the present disclosure, the structure has a double seal structure, and the space between the double seals in contact with the seal sheet through which fuel gas permeates is filled with oxidizing gas, so that fuel gas does not directly permeate to the refrigerant side. I can do it. In addition, by providing a through hole in the rib below the seal line of the cathode separator, which allows oxidizing gas to be supplied from the oxidizing gas flow path of the cathode separator to the space between the double seals, the gap between the double seals is always maintained. It is possible to maintain a state in which the fuel gas concentration in the space does not increase.

In this disclosure, the fuel gas and the oxidant gas are collectively referred to as a reaction gas. The reactive gas supplied to the anode is a fuel gas, and the reactive gas supplied to the cathode is an oxidant gas. The fuel gas is a gas mainly containing hydrogen, and may be hydrogen. The oxidant gas is a gas containing oxygen, and may be oxygen, air, dry air, or the like.

The fuel cell stack of the present disclosure has a cell stack in which a plurality of unit cells each having a cathode separator and an anode separator are stacked, and a seal sheet is used for sealing between adjacent unit cells.

The cell laminate is a laminate in which a plurality of single cells are stacked.
The number of stacked single cells in the cell stack is not particularly limited, and may be from 2 to several hundreds.

A single fuel cell cell typically comprises a membrane electrode gas diffusion layer assembly (MEGA).
The membrane electrode gas diffusion layer assembly includes an anode gas diffusion layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, and a cathode gas diffusion layer in this order.

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 a catalyst layer.
The catalyst layer may include, for example, a catalyst metal that promotes an electrochemical reaction, an electrolyte that has proton conductivity, a carrier that has electron conductivity, and the like.
As the catalyst metal, for example, platinum (Pt) and an alloy of Pt and another metal (for example, a Pt alloy mixed with cobalt, nickel, etc.) can be used.
The electrolyte may be a fluororesin or the like. As the fluororesin, for example, Nafion solution or the like may be used.
The catalyst metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalyst metal (catalyst-supporting carrier) and the electrolyte may coexist.
Examples of the carrier for supporting the catalytic metal include carbon materials such as carbon that are generally commercially available.

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 conductive member or the like having gas permeability.
Examples of the conductive member include carbon porous bodies such as carbon cloth and carbon paper, and metal porous bodies such as metal mesh and foamed metal.

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

The single cell includes two separators that sandwich both sides of the membrane electrode gas diffusion layer assembly. One of the two separators is an anode separator and the other is a cathode separator. In this disclosure, an anode separator and a cathode separator are collectively referred to as separators.
The separator may have holes such as supply holes and discharge holes for allowing fluids such as reaction gas and refrigerant to flow in the stacking direction of the unit cells. As the refrigerant, 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, a refrigerant supply hole, and the like.
Examples of the exhaust hole include a fuel gas exhaust hole, an oxidant gas exhaust hole, and a refrigerant exhaust hole.
The separator may have a reactive gas flow path on the surface in contact with the gas diffusion layer. Further, the separator may have a coolant flow path for keeping the temperature of the fuel cell constant on the surface opposite to the surface in contact with the gas diffusion layer.
The separator may have ribs forming channels such as a reaction gas channel and a coolant channel.
The separator may have seal line ribs that surround holes such as the supply hole and the discharge hole and are aligned with the seal line of the seal sheet on at least the surface on the refrigerant flow path side.
The anode separator may have a fuel gas flow path on the surface in contact with the anode side gas diffusion layer. Further, the anode separator may have a coolant flow path for keeping the temperature of the fuel cell constant on the surface opposite to the surface in contact with the anode side gas diffusion layer.
The cathode separator may have an oxidant gas flow path on the surface that contacts the cathode side gas diffusion layer. Further, the cathode separator may have a coolant flow path for keeping the temperature of the fuel cell constant on the surface opposite to the surface in contact with the cathode side gas diffusion layer.
The separator may be a gas-impermeable conductive member or the like. Examples of the conductive member include thermosetting resins, thermoplastic resins, resin materials such as resin fibers, carbon powder, and dense carbon made gas impermeable by compressing carbon materials such as carbon fibers. , a press-formed metal (for example, iron, aluminum, stainless steel, etc.) plate, etc. may be used. Further, the separator may have a current collecting function.
The shape of the separator may be a rectangle, a horizontally long hexagon, a horizontally long octagon, a circle, an oblong shape, or the like.

The reaction gas flow path of the separator may have a reaction gas inlet/outlet that is disposed adjacent to the reaction gas manifold and communicates with the reaction gas manifold. When the reaction gas flow path is an oxidant gas flow path, the reaction gas lead-in/out portion is an oxidant gas lead-in/out portion that communicates with the oxidant gas manifold, and when the reaction gas flow path is a fuel gas flow path, it is an oxidant gas lead-in/out portion that communicates with the oxidant gas manifold. This is a fuel gas inlet/outlet communicating with the manifold. The reactive gas lead-in/out part is a reactive gas introduction part when the reactive gas manifold is a reactive gas inlet manifold, and is a reactive gas outlet part when the reactive gas manifold is a reactive gas outlet manifold.
The reaction gas flow path may include a gas distribution section. The gas distribution section is disposed adjacent to the region of the reaction gas inlet/output section on the opposite side of the reaction gas manifold in the planar direction, and extends the gas flow from the reaction gas manifold to the power generation region or from the power generation region to the reaction gas manifold. This is the part that converges the gas flow. The gas distribution section has a structure that widens the gas flow on the inlet side of the reaction gas. The gas distribution section has a structure that converges the gas flow on the exit side of the reaction gas. The power generation region may be a region in which a membrane electrode gas diffusion layer assembly is arranged.

The single cell may include a resin frame.
The resin frame may be arranged around the outer periphery of the membrane electrode gas diffusion layer assembly, and may also be arranged between the cathode separator and the anode separator.
The resin frame may have a skeleton, an opening, and a hole.
The skeleton part is the main part of the resin frame connected to the membrane electrode gas diffusion layer assembly.
The opening is a holding area for the membrane electrode gas diffusion layer assembly, and is an area that penetrates a part of the skeleton to accommodate the membrane electrode gas diffusion layer assembly. The opening may be located in the resin frame at a position where the skeleton is located around the membrane electrode gas diffusion layer assembly (outer periphery), or may be located in the center of the resin frame.
The holes in the resin frame allow a fluid such as a reaction gas and a refrigerant to flow in the stacking direction of the unit cells. The holes in the resin frame may be aligned and arranged so as to communicate with the holes in the separator.
The resin frame may include a frame-shaped core layer and two frame-shaped shell layers provided on both sides of the core layer, that is, a first shell layer and a second shell 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.

The core layer may be a structural member having gas sealing properties 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 fuel cell manufacturing process. Specifically, the material of the core layer is, 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 (polyether sulfone), PPSU (polyphenylsulfone), LCP (liquid crystal polymer), epoxy resin, etc. It may also be made of resin or the like. The material of the core layer may be a rubber material such as EPDM (ethylene propylene diene rubber), fluorine rubber, silicone rubber, or the like.
The thickness of the core layer may be 5 μm or more, 30 μm or more from the viewpoint of ensuring insulation, and may be 100 μm or less, 90 μm or less from the viewpoint of reducing the cell thickness. It may be.

The first shell layer and the second shell layer have high adhesiveness with other substances and under the temperature conditions during thermocompression bonding, in order to bond the core layer and the anode separator and cathode separator to ensure sealing performance. It may be softened and have a lower viscosity and melting point than the core layer. Specifically, the first shell layer and the second shell layer may be made of thermoplastic resin such as polyester or modified olefin, or may be made of thermosetting resin 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 may be different types of resin. Providing shell layers on both sides of the core layer facilitates adhesion between the resin frame and the two separators by hot pressing.
The thickness of each of the first shell layer and the second shell layer may be 5 μm or more from the viewpoint of ensuring adhesiveness, or may be 30 μm or more from the viewpoint of reducing the cell thickness. , it may be 100 μm or less, or it may be 40 μm or less.

In the resin frame, the first shell layer and the second shell layer may be provided only in the portions bonded to the anode separator and the cathode separator, respectively. The first shell layer provided on one side of the core layer may be bonded to the cathode separator. The second shell layer provided on the other side of the core layer may be bonded to the anode separator. The resin frame may be sandwiched between a pair of separators.

The fuel cell stack may have a manifold in which each hole communicates, such as an inlet manifold with which each supply hole communicates, and an outlet manifold with which each discharge hole communicates.
Examples of the inlet manifold include a fuel gas inlet manifold, an oxidant gas inlet manifold, and a refrigerant inlet manifold.
Examples of the outlet manifold include a fuel gas outlet manifold, an oxidant gas outlet manifold, and a refrigerant outlet manifold.
In this disclosure, the fuel gas inlet manifold and the fuel gas outlet manifold are collectively referred to as the fuel gas manifold.
In the present disclosure, the oxidizing gas inlet manifold and the oxidizing gas outlet manifold are collectively referred to as the oxidizing gas manifold.
In this disclosure, a refrigerant inlet manifold and a refrigerant outlet manifold are collectively referred to as a refrigerant manifold.
A fuel cell stack has at least a fuel gas manifold, and typically further includes an oxidant gas manifold and a coolant manifold.

The seal sheet is placed between adjacent single cells and is used as a sealing member for the adjacent single cells.
The seal sheet may be made of thermoplastic resin such as polyester-based or modified olefin-based resin, or may be made of thermosetting resin such as modified epoxy resin.
The seal sheet may have a frame shape. The frame serving as the seal line of the seal sheet may be aligned with the seal line rib of the separator.
The seal sheet has a double seal structure including a first seal line that surrounds and seals the fuel gas manifold in a plan view, and a second seal line that surrounds the first seal line. The fuel gas manifold here may be a fuel gas inlet manifold, a fuel gas outlet manifold, or both manifolds.
The double seal structure has a double seal space between the first seal line and the second seal line.
Oxidizing gas is supplied to the rib of the cathode separator in contact with the second seal line from the oxidizing gas flow path of the cathode separator to the space between the double seals between the first seal line and the second seal line. A through hole is provided that penetrates the rib in the planar direction.
The space between the double seals has a structure that can be filled with oxidizing gas through the through hole.

In FIG. 1, the upper figure is a schematic plan view showing an example of the vicinity of the fuel gas manifold of the fuel cell stack of the present disclosure when viewed from above, and the lower figure is a schematic cross-sectional view taken along line AA.
As shown in the schematic plan view of FIG. 1, the seal sheet 24 of the fuel cell stack of the present disclosure includes a first seal line 11 that surrounds and seals the fuel gas manifold 10 in a plan view, and a second seal line 11 that surrounds the first seal line 11. It has a double seal structure with a seal line 13. Although not shown, the refrigerant manifold and the oxidizing gas manifold may be provided at any position outside the second seal line 13. The fuel gas manifold 10 may be a fuel gas inlet manifold or a fuel gas outlet manifold.
A double seal space 14 is formed between the first seal line 11 and the second seal line 13.
As shown in the AA cross-sectional schematic diagram, the fuel cell stack of the present disclosure includes a cathode separator 20 and an anode separator 22, and a resin disposed between the cathode separator 20 and the anode separator 22 in the vicinity of the fuel gas manifold 10. Adjacent single cells are sealed with a sealing sheet 24. The anode separator 22 has a fuel gas flow path 25 . The fuel gas passage 25 referred to here may be a fuel gas lead-in/out section.
As shown in the AA cross-sectional schematic diagram, oxidizing gas is supplied to the ribs of the cathode separator 20 that are in contact with the second seal line 13 from the oxidizing gas flow path of the cathode separator 20 to the space 14 between the double seals. A through hole 21 is provided that penetrates the rib in the planar direction. Oxidizing gas is supplied from the through hole 21 to the space 14 between the double seals, and the space 14 between the double seals is filled with the oxidizing gas. The double seal structure can prevent fuel gas from entering the refrigerant flow path.

10 Fuel gas manifold 11 First seal line 13 Second seal line 14 Space between double seals 20 Cathode separator 21 Penetration 22 Anode separator 23 Resin frame 24 Seal sheet 25 Fuel gas flow path

Claims (1)

A fuel cell stack having a cell stack in which a plurality of single cells each having a cathode separator and an anode separator are stacked, and using a seal sheet to seal between adjacent single cells,
The fuel cell stack has a fuel gas manifold,
The seal sheet has a double seal structure including a first seal line that surrounds and seals the fuel gas manifold in a plan view, and a second seal line that surrounds the first seal line,
The rib of the cathode separator in contact with the second seal line is provided with an oxidant gas from the oxidant gas flow path of the cathode separator to the space between the double seals between the first seal line and the second seal line. A through hole is provided that penetrates the rib in a planar direction, and is capable of supplying
The fuel cell stack has a structure in which the space between the double seals can be filled with the oxidizing gas through the through hole.