RU2328060C1 - Fuel element and fuel-cell battery - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention pertains to a fuel element and a fuel-cell battery with a polymer electrolytic membrane, using hydrogen as fuel and oxygen (in pure form or from the air) as an oxidising agent. According to the invention, in the fuel element there is an electrolytic membrane, electrodes, gas-diffusion collectors joined to a single construction - integrated membrane-electrode assembly with a frame made from polymer material. The membrane is sealed and the gas-diffusion collectors are strongly fixed to the frame. The membrane is protected from mechanical damages by the gas-diffusion collectors. Through putting an intermediate non-metallic netting in the current net collectors (between nets), allowing for formation of film flow, there is provision for conditions of removal of the water of reaction. A bipolar cooling fin, made in the form of a thin plate heat exchanger, provides for supplying reagents to the gas chambers of the fuel element and their outlet through several small channels in the frame of the bipolar cooling fin and openings in the side walls of the cooling fin, uniformly distributed on the width of the gas chambers. The channels at the input of the reagents are throttled. Sealing of component parts of the fuel element and the fuel elements in the battery is done using a glue bearing film, serving as an adhesive, without use of an elastomer lining and special glue.

EFFECT: simplification of the structure and better manufacturability of the fuel element; improved electrical characteristics and long-term performance of the battery; lowering of small-scale characteristics.

11 cl, 6 dwg

Description

The invention relates to the field of chemical current sources with direct conversion of chemical energy into electrical energy, namely to a fuel cell (TE) and a fuel cell battery (BTE) with a polymer electrolyte membrane using hydrogen as fuel and oxygen (in pure form or contained in air ) as an oxidizing agent.

BTE constructions with a polymer electrolyte membrane using hydrogen as fuel and oxygen in pure form, or contained in air as an oxidizing agent are known (see US Patents No. 5879826, 1999 No. 6207310 B1, 2001).

It is known that FC includes a hydrogen electrode, an oxygen electrode, a polymer electrolyte (membrane) located between the electrodes, as well as gas diffusion collector plates located on the hydrogen and oxygen sides for the distribution and supply of reagents to the membrane electrode assembly (MES) and current collectors. It is known that FCs in BFCs are separated by a bipolar plate in contact with current collectors. TEs can be assembled into the battery by stacking and screeding with covers and pins.

Of all the known BFC designs and the actual TE, the closest analogue of the presented invention is a TE with a metal distribution grid and a BFC based on this TE according to US patent No. 6207310 B1.

In accordance with this patent, the BFC consists of at least two FC separated by an electrically conductive thin bipolar cooling plate (BOP). BOP is made of thin metal foil and a metal wicker mesh located in the rectangular region of the frame, having an entrance in one corner and an exit in another, located diagonally to each other. The frame is sealed around the perimeter, forming a flow part for the cooling medium. In the hydrogen and oxygen chambers of the fuel cell, metal grids are also installed each in its own frame, which, like the BOP frame, has input and output channels located diagonally. Grids provide a uniform distribution of reagents on the surface of the electrodes.

MES is a complete assembly unit. The membrane is placed between two stainless steel frames (sheet thickness 0.254 mm) and sealed around the perimeter with adhesive. Gas diffusion electrodes from the hydrogen and oxygen sides are pressed onto the membrane. Mesh current collectors embedded in intermediate gaskets-frames are located on each side of the MES. The channels for supplying reagents to the gas chambers of the fuel cell are made directly in the intermediate gaskets-frames. The TE is sealed in the battery by compressing the intermediate gaskets-frames made of silicone tape reinforced with fabric. The compression ratio of the TE package in the battery is controlled and limited by the limiters provided for in the intermediate framework.

In the variant with a rigid combined polysulfone plastic frame excluding the intermediate gasket-frame, the TE is sealed in the battery with a special adhesive applied to both surfaces of the rigid plastic frame.

Current grid collectors are made of a set of grids with small and large cells. The mesh with small cells is in contact with gas diffusion collectors. The surface of these nets is hydrophobized with a composition of carbon and teflon to prevent water droplets from accumulating in the cells.

The disadvantages of the technical solutions implemented in the analogue are:

1. The lack of protection of the membrane around the perimeter in places of sealing and contact of gas diffusion collectors and metal frames from mechanical damage and possible damage.

2. Concentrated (local) supply / removal of working fluids in the fuel cell, which does not guarantee uniform distribution of fluids over the surface of the electrodes in a wide range of flow rates.

3. Possible “sticking” of water in the cells of the grid current collectors and the formation of sections in the grids with water-filled cells, which exclude the supply of reagents to the electrodes and lead to a decrease in the efficiency of the electrodes.

4. The presence of intermediate gaskets-frames for placement of grid current collectors, complicating the design of the fuel cell and doubling the number of mating surfaces requiring sealing (for the variant with intermediate frames).

5. Certain restrictions on minimizing the gap in the gas chambers of the fuel cell, associated with the need to form channels that communicate the collector system of the battery with gas chambers of the fuel cell directly within the fuel cell, subject to the requirements for frame strength and permissible channel sizes.

SUMMARY OF THE INVENTION

In order to eliminate the above-mentioned disadvantages of TE according to US patent No. 6207310 B1, simplify the design and increase the reliability of TE, the subject of the present invention can include TE and BFC with a polymer electrolyte membrane using hydrogen and oxygen in pure form or contained in air.

The fuel cell includes a hydrogen electrode, an oxygen electrode located between the electrodes, a polymer electrolyte, hydrogen and oxygen gas diffusion collectors, current collectors made of metal grids. Adjacent TEs in the battery are separated by a BOP made in the form of a plate heat exchanger made of thin metal foil and a metal mesh inside to distribute the cooling medium over the surface of the heat exchanger and remove heat generated in the TE. BOP has contact with current collectors and also performs the function of transmitting electricity. TEs with the help of covers and pins are collected in the battery.

Features of the invention are:

1. MES, in which gas diffusion collectors together with the membrane are embedded in the groove of the polymer frame, providing protection of the membrane over the entire surface. The membrane and collectors in the frame are sealed with a sealant placed in the free space of the groove along the membrane perimeter beyond the electrodes, and with an adhesive film located in the seal assembly.

The design of the MES frame simultaneously provides for the placement of grid current collectors in it above the gas diffusion collectors, eliminating the need for intermediate frames.

2. The BOP consists of two sheets of thin foil (from the hydrogen and oxygen sides) and metal meshes located between them and a frame with channels on the peripheral surface for supply through the BOP and uniform distribution of reagents on the surface of the electrodes. In the rectangular field of the frame, partitions are provided for organizing the flow of the cooling medium through the grids according to the “serpentine” principle.

3. Another feature of the invention is the placement of thin mesh material in the grid current collectors of the hydrogen and oxygen chambers of the fuel cell, capable of changing the wetting angle of water droplets and promoting the formation of film flow along the surface of the grids, ensuring the natural runoff of water into the collector system of the fuel cell and battery.

4. A further feature of the invention is a TE sealing assembly in a battery consisting of at least two TE separated by a BOP, using an adhesive transfer film that functions as an adhesive, without the use of gaskets made of elastomer or special glue.

List of drawings

Figure 1 presents the MES.

Figure 2 presents the BOP.

Figure 3 presents the frame of the BOP.

Figure 4 presents the oxygen plate of the BOP.

Figure 5 presents the hydrogen plate of the BOP.

Figure 6 presents a simplified diagram of the fuel cell.

Information confirming the possibility of implementing the invention

In accordance with the invention, MES TE (Fig. 1) consists of a polymer membrane (1), two electrodes, gas diffusion collectors of hydrogen and oxygen (2) located on both sides of the membrane, and a polymer (for example, polycarbonate) frame (3) with a groove along the inner contour in which the sealing unit of the membrane and gas diffusion collectors is formed. The frame can be made of three parts (option 1) made of sheet material: two outer (4) and one middle (5).

The middle part (5) has a smaller width, as a result of which, when the frame is assembled, a groove is formed on its inner side, into which a membrane with electrodes and gas diffusion layers is laid. The membrane is sealed with a sealant (6) placed in the free space of the groove along the perimeter of the membrane outside the electrodes. To increase the reliability and increase the strength of the sealing unit between the frame material, the sealant and the gas diffusion layers, an adhesive transfer film is laid, which performs the function of an adhesive layer (7). The frame parts are also connected and sealed with an adhesive film. One of the outer parts of the frame, in the area of the sealant, has holes (8), evenly spaced around the perimeter of the frame, to remove excess sealant during assembly and to prevent it from being squeezed out into the internal space onto diffusion collectors. Holes are provided on the peripheral surface of the frame, which, when assembling the fuel cell stack, are combined with similar holes in the BOP and parts of neighboring fuel cells, forming a collector system for supplying (removing) reagents, reaction products, and a cooling medium. Holes (9) form the collector system in oxygen, holes (10) in hydrogen, holes (11) in the cooling medium.

The frame can be made of two plates in which the platforms for the formation of the groove are prepared (option 2).

Gas diffusion collectors, having a seal in the frame, protect the membrane from possible mechanical damage during assembly of the FC package and its compression, as well as during operation, being, in essence, a protective element for the membrane.

BOP (figure 2) consists of a frame (12), on both sides of which are hydrogen (13), oxygen (air) plates (14). A distribution grid (15) is placed in the rectangular field of the frame.

The frame (12) and the plates (13, 14) are interconnected and sealed with an adhesive film (16).

The design of the BOP provides for the combination of the following functions in the fuel cell:

- removal of heat generated in the fuel cell;

- transmission of electrical energy;

- supply and distribution of reagents on the surface of gas diffusion collectors (electrodes);

- removal of reaction products.

The fulfillment of these functions is ensured by the design of the framework, which is the defining part of the BOP. The frame (figure 3) is made of a sheet of conductive or non-conductive material. In the central window of the frame (17), in the area of the distribution grid, partitions (18) are provided that provide a “serpentine” flow around the distribution grid (15). A system of holes and channels is provided on the peripheral surface of the frame. Holes (19) are used to form a collector system at the oxygen inlet, holes (20) - at the oxygen outlet, holes (21) - at the hydrogen inlet, holes (22) - at the hydrogen outlet, holes (23) - at the inlet of the cooling medium, openings (24) - at the outlet of the cooling medium. Channels (25, 26, 27, 28, 29, 30) communicate battery collector systems with a TE oxygen chamber (channels 25, 26), with a TE hydrogen chamber (channels 27, 28), and with an internal BOP cavity streamlined by the cooling medium (channels 29, 30). The oxygen supply channels (25) and hydrogen supply channels (27) have local constrictions (31), which, when assembling BOP with plates (13, 14), form throttle channels providing uniform distribution of reagents along the input channels. The collector systems of reagents are uniformly distributed over the width of the oxygen and hydrogen chambers, which ensures, taking into account the input throttling of each channel, a uniform distribution of reagents over the chambers.

The oxygen (air) plate (14) of the BOP (Fig. 4) has mating holes (19, 20, 21, 22, 23, 24) of the collector system, as well as holes (32, 33), which when the plate is applied to the frame (12 ) report the channels (25, 26) of the frame with the oxygen chamber of the fuel cell. The channels (27, 28) of the frame are blocked by an oxygen plate, excluding the communication of hydrogen channels with the oxygen chamber.

The BOP hydrogen plate (Fig. 5) also has openings (19, 20, 21, 22, 23, 24) of the collector system and openings (34, 35), which, when the plate is applied to the frame (12), communicate with the channels (27, 28) frames with a hydrogen cell fuel cell. The channels (25, 26) of the frame are blocked by a hydrogen plate, excluding the communication of the oxygen channels with the hydrogen chamber. Thus, the reagents from the collector system through the channels in the frame and the holes in the hydrogen and oxygen plates enter: hydrogen - only into the hydrogen chamber, oxygen (air) - only into the oxygen chamber, in this connection there is no need for intermediate frames for supplying the reagents to hydrogen and oxygen chambers. The current grid collectors in this case are located in the central field of the MES, and the gap in the chambers is regulated by the height of the frame above the gas diffusion collectors.

The connection of the BOP components with each other and their sealing along the mating surfaces is carried out by an adhesive transfer film with adhesive properties.

Figure 6 shows a simplified diagram of one fuel cell, which includes MES (36), BOP (37), current grid collectors in the hydrogen (38) and oxygen (39) chambers. All TE components have electrical and mechanical contact with each other. Mesh current collectors are made of at least two grids - with small cells on the side of the gas diffusion collector and with large cells on the side of the BOP. Between the metal grids, an intermediate grid (40) of natural (e.g., cotton) or synthetic material with the properties of changing the wetting angle of water droplets and promoting the formation of a film flow along the grids and BOP plates is placed.

A system of at least two fuel cells forms a battery of fuel cells separated by a BOP. The sealing of the fuel cells with each other in the battery is carried out by an adhesive-transfer film that performs the functions of an adhesive.

The technical result of the proposed invention is to simplify the design and improve the manufacturing technology of TE and the TE battery, increase the electrical and resource characteristics of the TE and the TE battery, reduce the overall dimensions of the battery.

The claimed technical result is achieved by the following technical solutions:

- a polymer electrolyte (membrane) with electrodes, hydrogen and oxygen gas diffusion collectors by means of a polymer frame are combined into a single integrated MES;

- in an integral MES, a membrane with electrodes and gas diffusion collectors is placed in the groove of the frame and sealed with a sealant located in the free volume of the groove in the frame around the perimeter of the membrane outside the electrodes and gas diffusion collectors;

- for the reliability of sealing and increase the strength of the seal between the frame, the sealant and the gas diffusion manifolds, an adhesive transfer film has been laid out that performs the functions of an adhesive layer;

- in the integrated MES, gas diffusion collectors together with the membrane are embedded in the frame, covering the entire surface of the membrane with the exception of the sealing area of the membrane, and protect the membrane from possible mechanical damage;

- in the integrated MES, in the area of the membrane sealing assembly, one of the frame plates has openings for removing excess sealant evenly spaced around the membrane;

- grid current collectors in the fuel cell are placed and fixed in the central rectangular region of the integrated MES frame; and the degree of compression of the active (central) region of the integrated MES is ensured by the specified excess of the thickness of the grid current collectors over the thickness of the MES frame from the level of gas diffusion collectors;

- in the current grid collectors (between the grids) there is a non-metal grid made of natural (for example, cotton) or synthetic material that has the ability to change the wetting angle of water droplets and the ability to form a film flow along the grids and the surface of the BOP;

- The BOP also performs the function of supplying and distributing reagents (hydrogen, oxygen, air) through the hydrogen and oxygen chambers of the fuel cell and removing reaction products through channels in the frame of the BEC communicating the collector system of the battery through hydrogen and oxygen with the corresponding gas chamber of the fuel cell through openings in the side plates BOP;

- in the central window of the BOP frame, in the area where the metal distribution grid is placed, partitions are provided that provide a “serpentine” flow around the distribution grid inside the BOP with a number of strokes of at least three;

- the supply of reagents to the gas chambers of the fuel cell and their removal is carried out through many small channels in the frame and holes in the side plates of the BOP, evenly distributed across the width of the gas chamber, and the channels at the inlet of the reagents in the gas chambers are throttled;

- minimizing the thickness of the fuel cell and, as a result, the dimensions of the battery of the fuel cell by minimizing the gap in the gas chambers of the fuel cell, provided by the principle of supplying reagents to the fuel cell through the BOP, and minimizing the gap between the side plates of the BOP;

- connection and sealing of fuel cells with each other in a bag with an adhesive film without the use of gaskets made of elastomer and special glue.

Claims (11)

1. A fuel cell comprising a hydrogen electrode, an oxygen (air) electrode located between the electrodes, a polymer electrolyte (membrane), hydrogen and oxygen (air) gas diffusion collectors, current collectors of at least 2 metal grids, characterized in that a polymer electrolyte (membrane) with electrodes, hydrogen and oxygen gas diffusion collectors through a polymer frame are combined into a single integral membrane-electrode assembly. 2. The fuel cell according to claim 1, characterized in that in the integral membrane-electrode assembly a membrane with electrodes and gas diffusion collectors is placed in the groove of the frame and sealed with a sealant located in the free volume of the groove in the frame around the perimeter of the membrane outside the electrodes and gas diffusion collectors. 3. The fuel cell according to claim 2, characterized in that between the frame, the sealant and the gas diffusion manifolds an adhesive transfer film is laid, which acts as an adhesive layer. 4. The fuel cell according to claim 2, characterized in that in the integral membrane-electrode assembly gas diffusion manifolds together with the membrane are embedded in the frame, covering the entire membrane surface, with the exception of the membrane sealing area, and protect the membrane from possible mechanical damage. 5. The fuel cell according to claim 2, characterized in that in the integral membrane-electrode assembly, in the region of the membrane sealing assembly, one of the frame plates has openings for removing excess sealant evenly spaced around the perimeter of the membrane. 6. The fuel cell according to claim 1, characterized in that the grid current collectors are placed and fixed in the Central rectangular region of the frame of the integrated membrane-electrode assembly, while the degree of compression of the working area of the integrated membrane-electrode assembly is provided by a specified excess thickness of the grid current collectors over the thickness membrane-electrode assembly framework, from the level of gas diffusion collectors. 7. The fuel cell according to claim 1 or 6, characterized in that in the current grid collectors (between the grids) an intermediate grid of natural (eg, cotton) or synthetic material is placed, which has the ability to change the wetting angle of water droplets and contribute to the formation of film flow along the nets and surface of the bipolar cooling plate. 8. A fuel cell battery consisting of at least 2 fuel cells, each of which includes a hydrogen electrode, an oxygen (air) electrode located between the electrodes, a polymer electrolyte (membrane), hydrogen and oxygen (air) gas diffusion collectors, current collectors made of metal grids and a bipolar cooling plate for separating adjacent fuel elements made in the form of a thin plate heat exchanger with a frame and a metal grid inside the frame, characterized by that the fuel cells are made according to any one of claims 1 to 7, the frame of the bipolar cooling plate is equipped with channels and holes for supplying and distributing reagents (hydrogen, oxygen, air) through the hydrogen and oxygen chambers of the fuel cell and removing reaction products, and the side walls adjacent to the hydrogen and oxygen chambers of the fuel cells, equipped with holes for communicating the collector systems of the battery through hydrogen and oxygen (air) with the corresponding gas chamber of the fuel cell. 9. The fuel cell battery according to claim 8, characterized in that in the central window of the frame of the bipolar cooling plate in the area where the metal mesh is placed, partitions are provided that provide a “serpentine” flow around the mesh inside the bipolar cooling plate with at least three strokes. 10. The fuel cell battery according to claim 8, characterized in that the supply of reagents to the gas chambers of the fuel cell and their removal is made through many small channels in the frame of the bipolar cooling plate and holes in the side walls of the bipolar cooling plate, uniformly distributed across the width of the gas chamber, and the channels at the inlet of the reactants in the gas chambers are throttled. 11. The fuel cell battery according to claim 8, characterized in that the connection and sealing of the fuel cells in a package is carried out by an adhesive transfer film that performs the function of an adhesive, without the use of gaskets made of elastomer and special glue.

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