JP2024116467A - Fuel Cell Stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell stack that is easy to disassemble.

SOLUTION: A fuel cell stack includes a cell laminate in which a plurality of unit cells are stacked, an adhesive sheet is used to seal between adjacent unit cells, and when the unit cells are disassembled from the adhesive sheet, the adhesive sheet between the adjacent unit cells is cut and disassembled, and a heat-inducing material is sealed in a rubber layer of the adhesive sheet.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

This disclosure relates to a fuel cell stack.

Various technologies have been proposed regarding fuel cells (FCs), such as those disclosed in Patent Document 1.

JP 2022-079927 A

There is a fuel cell in which the cells are bonded and sealed with an adhesive sheet, as disclosed in Patent Document 1.
When a cell (hereinafter sometimes referred to as a single cell) needs to be replaced due to a malfunction of the cell or damage to a part, the adhesive sheet will not peel off naturally because it is attached to the cell by its adhesive strength. However, since the adhesive strength increases over time and due to a history of high temperatures, it is not easy to cut and there is a risk of damaging the cell when the fuel cell stack is disassembled.
For example, there is a method of disassembling the cells by cutting the rubber layer of the adhesive sheet with a thin wire as a disassembly tool, but in a rubber layer that has hardened, the rubber layer is too hard and difficult to cut, making it difficult to disassemble the cells.
In addition, excessive input or heat applied to the adhesive sheet during disassembly may adversely affect surrounding components. Also, a thermostatic chamber is required to heat the entire fuel cell stack, which is a heavy workload and inefficient.
Therefore, if an adhesive sheet is used to bond and seal between the cells, it is difficult to disassemble the fuel cell stack for each cell to be replaced, resulting in poor work efficiency and requiring a great deal of man-hours.

This disclosure was made in light of the above situation, and its main objective is to provide a fuel cell stack that is easy to disassemble.

The present disclosure provides a fuel cell stack having the following features:
A fuel cell stack having a cell laminate in which a plurality of unit cells are stacked, an adhesive sheet is used to seal between adjacent unit cells, and the adhesive sheet between adjacent unit cells is cut and disassembled when the unit cells are disassembled from the adhesive sheet,
A fuel cell stack, wherein a heat-generating material is enclosed in the rubber layer of the pressure-sensitive adhesive sheet.

The fuel cell stack of the present disclosure can be easily disassembled.

FIG. 1 is a schematic diagram showing an example of a cross-section of a seal made by an adhesive sheet between individual cells before disassembly of a fuel cell stack according to the present disclosure, and FIG. 2 is a schematic diagram showing an example of a cross-section of a seal made by an adhesive sheet between individual cells after disassembly of a fuel cell stack according to the present disclosure. 2 is a cross-sectional schematic diagram showing an example of an adhesive sheet provided in a fuel cell stack according to the present disclosure. FIG.

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 range of values means that the 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.

The present disclosure provides a fuel cell stack having the following features:
A fuel cell stack having a cell laminate in which a plurality of unit cells are stacked, an adhesive sheet is used to seal between adjacent unit cells, and the adhesive sheet between adjacent unit cells is cut and disassembled when the unit cells are disassembled from the adhesive sheet,
A fuel cell stack, wherein a heat-generating material is enclosed in the rubber layer of the pressure-sensitive adhesive sheet.

FIG. 1 is a schematic diagram showing an example of a cross-section of a seal made by an adhesive sheet between individual cells before disassembly of a fuel cell stack according to the present disclosure, and FIG. 1 is a schematic diagram showing an example of a cross-section of a seal made by an adhesive sheet between individual cells after disassembly of a fuel cell stack according to the present disclosure.
As shown in FIG. 1, according to the present disclosure, by incorporating a heat-inducing material into the rubber layer of the adhesive sheet, the rubber layer of the adhesive sheet generates heat when cut with a wire, creating a structure in which the hardened rubber is softened by the heat generated by the heat-inducing material to make it easier to cut, thereby making it easier to cut the adhesive sheet when disassembling a single cell.
As a result, the fuel cell stack can be easily disassembled into individual unit cells without damaging the unit cells, and the unit cells can be reused.
In addition, since the only part that generates heat is the rubber layer of the adhesive sheet, damage to components inside the unit cell can be reduced.
Furthermore, since there is no need to heat the entire fuel cell stack, the amount of work required for disassembly can be reduced.

In this disclosure, the fuel gas and the oxidant gas are collectively referred to as reactant gas or gas. The reactant gas supplied to the anode is the fuel gas (sometimes referred to as the anode gas), and the reactant gas supplied to the cathode is the oxidant gas (sometimes referred to as the cathode 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.

The fuel cell stack of the present disclosure has a cell stack in which multiple single cells are stacked, and an adhesive sheet is used to seal between adjacent single cells. When disassembling the single cells from the adhesive sheet, the adhesive sheet between the adjacent single cells is cut and disassembled.
In this disclosure, both the single cell and the fuel cell stack may be referred to as a fuel cell.

Examples of a method for cutting the adhesive sheet between the single cells to disassemble the unit cells include a method in which the adhesive sheet is cut using a disassembly tool for cutting adhesive sheets.
The disassembly tool may be anything capable of cutting the adhesive sheet, and may be, for example, a wire, a blade, a spatula, or the like.

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 single fuel cell 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.

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 present together.
The support for supporting the catalytic metal may be, for example, a carbon material such as carbon that is generally available commercially.

The cathode side gas diffusion layer and the anode side gas diffusion layer are collectively referred to as a gas diffusion layer (GDL).
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.

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

The single cell may have a resin frame.
The resin frame is disposed around the outer periphery of the membrane electrode gas diffusion layer assembly, and is disposed between the cathode separator and the anode separator.
The resin frame may have a framework, an opening, and a hole.
The framework is the main part of the resin frame 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 framework to accommodate the membrane electrode-gas diffusion layer assembly. The opening may be located at a position in the resin frame where the framework is disposed around (the outer periphery of) the membrane electrode-gas diffusion layer assembly, and may be located in the center of the resin frame.
The holes in the resin frame allow reaction gases and fluids such as a cooling medium 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 separators.
The resin frame may have a three-layer structure including a frame-shaped core layer and two frame-shaped shell layers, i.e., 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, similar to the core layer.
The material of the core layer may be, for example, polyethylene, polypropylene (PP), 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), resin such as epoxy resin, etc. The material of the core layer may be a rubber material such as EPDM (ethylene propylene diene rubber), fluorine-based rubber, silicone-based rubber, etc.
The material of the shell layer may be a thermoplastic resin such as a polyester-based or modified olefin-based resin, or may be a thermosetting resin such as a 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.

The single cell includes a pair of separators that sandwich a membrane electrode gas diffusion layer assembly. One of the pair of separators is an anode side separator, and the other is a cathode side separator. In the present disclosure, the anode side separator and the cathode side separator are collectively referred to as separators.
The separator may have holes forming manifolds such as supply holes and exhaust holes for passing fluids such as reactant gases and cooling media in the stacking direction of the unit cells.
As the cooling medium, cooling water such as a mixed solution of ethylene glycol and water can be used to prevent freezing at low temperatures, or cooling air can be used as the cooling medium.
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.
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 for maintaining a constant temperature of the fuel cell.
The separator may be a gas-impermeable conductive member. The conductive member may be, for example, dense carbon made by compressing carbon to make it gas-impermeable, or a press-formed metal (e.g., iron, aluminum, stainless steel, etc.) plate. The separator may also have a current collecting function.
The shape of the separator may be rectangular, horizontally elongated hexagonal, horizontally elongated octagonal, circular, oval, or the like.

The separator may have ribs that define flow paths such as a reactant gas flow path and a coolant flow path.
The pair of separators may have a seal line rib on the pressure-sensitive adhesive sheet side to form a seal line with the pressure-sensitive adhesive sheet. The seal line rib may be arranged so as to surround holes such as supply holes and discharge holes when viewed from above, or may be arranged along the outer periphery of the separator so as to surround all of these multiple holes. The seal line rib may also be arranged in alignment with the seal line of the pressure-sensitive adhesive sheet.

The fuel cell stack has manifolds, such as an inlet manifold to which the supply holes communicate, and an outlet manifold to which the exhaust holes communicate.
Examples of the inlet manifold include an anode inlet manifold, a cathode inlet manifold, a coolant inlet manifold, etc. The anode inlet manifold and the cathode inlet manifold are collectively referred to as a gas inlet manifold.
Examples of the outlet manifold include an anode outlet manifold, a cathode outlet manifold, a cooling medium outlet manifold, etc. The anode outlet manifold and the cathode outlet manifold are collectively referred to as a gas outlet manifold.
The gas inlet manifold and the gas outlet manifold are collectively referred to as the reaction gas manifold.

The adhesive sheet is disposed between adjacent unit cells and is used as a sealing member for the adjacent unit cells.
The pressure-sensitive adhesive sheet may be shaped like a frame. The frame that forms the seal line of the pressure-sensitive adhesive sheet may be aligned with the seal line rib of the separator. The pressure-sensitive adhesive sheet may be shaped to cover the entire surface of the separator except for the holes of the separator.
The width of the frame that forms the seal line of the pressure-sensitive adhesive sheet may be the same as the width of the seal line rib of the separator, or may be larger than the width of the seal line rib of the separator.
The pressure-sensitive adhesive sheet may seal the periphery of the hole so as to surround the hole constituting the reaction gas manifold in a plan view, or may seal the outer periphery of the separator. The reaction gas manifold referred to here may be an anode inlet manifold, an anode outlet manifold, a cathode inlet manifold, or a cathode outlet manifold.
The pressure-sensitive adhesive sheet may seal the periphery of the holes so as to surround the holes constituting the anode inlet manifold, the holes constituting the anode outlet manifold, the holes constituting the cathode inlet manifold, and the holes constituting the cathode outlet manifold in a plan view, and may also seal the outer peripheral edge of the separator. The pressure-sensitive adhesive sheet may cover the entire surface of the separator except for the holes of the separator.
The thickness of the pressure-sensitive adhesive sheet is not particularly limited and may be 10 to 100 μm.

The pressure-sensitive adhesive sheet has at least a rubber layer. The pressure-sensitive adhesive sheet may have a three-layer structure including a rubber layer and a pair of pressure-sensitive adhesive layers sandwiching the rubber layer.
Examples of materials for the rubber layer include EPDM (ethylene propylene diene rubber), fluorine-based rubber, and silicon-based rubber.
The thickness of the rubber layer is not particularly limited and may be 5 to 90 μm.
The pair of adhesive layers is collectively referred to as an adhesive layer.
The material of the adhesive layer may be, for example, a thermoplastic resin such as a polyester or modified olefin resin, or a thermosetting resin such as a modified epoxy resin.
The pair of adhesive layers may be made of the same material or different materials, and the adhesive strength between one adhesive layer and the separator may be different from the adhesive strength between the other adhesive layer and the separator.
The shape of the adhesive layer is the same as that of the adhesive sheet.
The thickness of the adhesive layer is not particularly limited and may be 5 to 50 μm.
The pair of adhesive layers may have the same thickness or different thicknesses.

FIG. 2 is a schematic cross-sectional view showing an example of an adhesive sheet provided in the fuel cell stack of the present disclosure.
The adhesive sheet shown in FIG. 2 has a three-layer structure consisting of a rubber layer and a pair of adhesive layers sandwiching the rubber layer.
The rubber layer contains a heat-generating material.
The heat-inducing material may be metal particles.
By incorporating metal particles into the rubber layer, frictional heat can be generated when the rubber layer of the adhesive sheet between the single cells of the fuel cell stack is cut, heating the rubber layer and softening the rubber layer to make it easier to cut.
The heat-inducing material may be a material that generates heat when exposed to air, such as iron powder, water, a water-retaining material, activated carbon, and salt.
The material that generates heat when exposed to air may be packed into microcapsules and sealed in the rubber layer. This allows the microcapsules to be broken by the wire when the fuel cell stack is disassembled between the single cells, and the material that generates heat when exposed to air to heat the rubber layer when exposed to air, softening the rubber layer and making it easier to cut.

Claims (1)

A fuel cell stack having a cell laminate in which a plurality of unit cells are stacked, an adhesive sheet is used to seal between adjacent unit cells, and the adhesive sheet between adjacent unit cells is cut and disassembled when the unit cells are disassembled from the adhesive sheet,
A fuel cell stack, wherein a heat-generating material is enclosed in the rubber layer of the pressure-sensitive adhesive sheet.

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