JPH01272054A - Integrated unit of fuel cell and its assembly - Google Patents

Abstract

PURPOSE: To integrate fuel cells with each other in the dry condition by providing a pair of opposite electrodes and a base material means between a first and a second plates, and providing a base material means with a paper, which can assemble a fuel cell before adding electrolyte. CONSTITUTION: A fuel cell 10, which can be integrated with each other in the dry condition, has a first plate 12 and a second plate 14 opposite to each other. A pair of opposite electrodes 16 are positioned between the first and the second plate 12, 14, and the base material 18 is arranged between the pair of electrodes 16. The base material 18 is formed of a layer of silicon carbide and a layer of paper having a sufficient porosity, and the fuel cell 10 can be assembled before applying the electrolyte to the base material 18. Sufficient porosity is given to the base material 18 so that the electrolyte can be sufficiently moved in the dry base material 18 from an edge part thereof in the lateral direction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates generally to a fuel cell assembly capable of converting the latent chemical energy of a fuel into electricity, and more particularly to a fuel cell assembly capable of converting the latent chemical energy of a fuel into electricity, and more particularly, in a dry state. That is, it relates to a fuel cell that can be integrated before being filled with electrolyte.

BACKGROUND OF THE INVENTION Fuel cells, which are used to convert the latent chemical energy of fuel directly into electricity, are well known in the art.

For example, as described in US Pat. No. 4,483,088. This type of fuel cell is based on various electrochemical reactions. One of the well-known reactions uses hydrogen as a fuel and generates electricity by the reaction of hydrogen and oxygen.

One common structure for hydrogen-oxygen batteries is a stacked structure, in which the anode and cathode electrodes are separated by a porous material that holds an electrolyte, such as concentrated phosphoric acid. . Hydrogen is conducted through a passage behind the active area of the anode and oxygen is conducted through a passage behind the active area of the cathode. A catalyst such as platinum is attached to the surfaces of the anode and cathode.

In the presence of a catalyst, hydrogen gas dissociates at 7 nodes,
becomes hydrogen ions and electrons. Hydrogen ions migrate as an ionic current through the electrolyte to the cathode, and electrons travel through an external circuit to the cathode.

At the cathode, hydrogen ions, electrons, and oxygen molecules combine to produce water.

It is known that the electrolyte contained in the matrix expands or contracts during operation due to changes in operating conditions. It is also expected that over time some of the electrolyte will be consumed and the volume of electrolyte in the matrix will decrease. It was also intended to solve problems associated with electrolyte volume changes and electrolyte depletion. For example, U.S. Pat.
No. 83,088, an electrolyte dispensing system is disclosed in which a set of electrolyte vessels are coupled to respective fuel cells. The electrolyte is stored separately to ensure that the electrolyte of each integrated cell is electrically isolated.
The individual storage compartments are joined by tubes containing fibrous wicks, each tube end terminating in a means for drawing electrolyte into each fuel cell, the 8 tubes being heat-shrinked tightly with the internal L&M. is combined with Such a configuration allows electrolyte to be supplied to the matrix to compensate for its shrinkage or consumption. However, it cannot accept acid if its volume expands due to changing conditions during operation.

<Problems to be Solved by the Invention> An object of the present invention is to enable fuel cell assemblies to be assembled in a dry state. Dry integration of fuel cell assemblies provides several advantages. First, when an acid electrolyte is used, the concentration and volume of the acid change depending on the humidity (moisture) in the air at the time of accumulation. Therefore, it is necessary to assemble the fuel cell assembly in an environment with precisely controlled humidity. This complicates assembly and increases the cost of the fuel cell assembly. Furthermore, if the fuel cell assembly can be assembled in a dry state, the time required for assembly will be reduced and less skilled workers can be used for assembly work. Finally, if a fuel cell assembly can be assembled in a dry state, there is no problem with storing it for an indefinite period of time before assembly.Currently, fuel cell assemblies are assembled in a wet state. Therefore, if the fuel cell assembly had to be stored for a period of time, the environment had to be controlled so that the acid concentration and volume did not change significantly and carbon corrosion was minimized. These types of complex storage problems have unnecessarily increased the price of fuel cell assemblies and diminished their marketability.

Means for Solving Problems> The present invention relates to a fuel cell that can be integrated in a dry state. The fuel cell has opposed first and second plates. A pair of opposing electrodes are located between the first plate and the second plate, and a matrix is disposed between the pair of electrodes. The matrix consists of a layer of silicon carbide and a layer of paper with sufficient porosity, and is configured to allow the fuel cell to be assembled prior to adding electrolyte to the matrix. Fuel cells are
Furthermore, it has a mechanism for supplying electrolyte to the base material.

Most prior art fuel cells have been found to have low lateral electrolyte mobility due to low matrix porosity. If the lateral mobility is low, the electrolyte cannot be introduced into the dry matrix from the edges of the matrix.

The present invention solves the above problem by providing the matrix with sufficient porosity to allow sufficient lateral movement of the electrolyte from the edges of the matrix into the dry matrix. The porosity of the base material is made sufficiently high while maintaining other properties of the base material, such as resistance to pressure differences associated with process losses and low internal wire resistance, within acceptable limits. .

The fuel cell of the present invention provides an effective means of assembling a dry fuel cell assembly.The method of the present invention includes the step of positioning the first electrode on top of the plate. A high porosity matrix is placed on top of the first electrode, a second electrode is placed on top of the matrix, and a plate is placed on top of the second electrode. Repeat the above steps until the desired number of batteries are accumulated.

The apparatus and method of the present invention is a significant advance over conventional methods. Since the fuel cell assembly can be assembled in a dry state, there is no need to assemble the assembly in a controlled environment. Since the stack is assembled in a dry state, the time required is short and unskilled workers can be used. After the assembly is assembled, the assembly can be stored under normal storage conditions. These advantages can reduce the price of the fuel cell assembly and further improve the marketability of the fuel cell. These and other advantages of the invention will become apparent from the following description of the preferred embodiment.

<Embodiments> In order to clearly understand and easily carry out the invention as described in the claims, preferred embodiments will be described with reference to the accompanying drawings. The following preferred embodiments are included for illustrative purposes only.

This is not intended to limit the invention.

One fuel cell 10 constructed in accordance with the teachings of the present invention is shown in FIG.
2 and a lower bipolar plate 14, and an anode electrode 16, a base material 18, and a cathode electrode 20 are sandwiched between these bipolar plates. Play) 12 and 14
is made of a material such as, for example, a compression molded graphite-resin composite. Electrodes 16 and 20 are comprised of porous graphite material or the like with a porous fiber backing (not shown) to increase structural integrity. The base material 18 has a layer of high porosity paper 22 which allows an electrolyte such as phosphoric acid to migrate laterally from one end into the bone dry material 18. The TO layer 22 must have sufficient porosity to allow
It was found that paper with a thickness of approximately 0.1 mil (4 mil), sold under the trade name RAY TGP 30, can be used. The porous paper layer 22 needs to be extremely thin to avoid loss of cell voltage due to internal ionic resistance. The matrix 18 also has a porous layer of silicon carbide on the order of 5 mils thick.

The various passageways within the fuel cell 10 are shown in FIG. 2; oxidizer or other oxygen-containing material such as air flows through the acetate passages, such as channel 26, and hydrogen-rich fuel flows through the fuel channels. 28. When multiple fuel cells are stacked, the bipolar plates 12 located between the cells are
The oxidant gas for one cell is supplied from one side, and the fuel gas is supplied from the other side to the adjacent cell. A manifold (not shown) is typically used to supply oxidant to oxidant inlet 30 of oxidant channel 26 and to receive oxidant from oxidant outlet 34 of oxidant channel 26 . A similar manifold (not shown) is used to supply fuel to the fuel inlet 38 of the fuel channel 28 and to receive fuel from the fuel outlet 42 of the fuel channel 28.

Turning now to FIG. 3, there is shown a fuel cell assembly 58 having the improved internal electrolyte supply system of the present invention. The assembly 58 is a stack of multiple fuel cells. The fuel cell has an upper bipolar plate 12 and a lower bipolar plate 14, between which a lower anode electrode 1 is arranged.
6, an electrolyte-containing porous base material, an electrolyte-containing upper porous base material (both base materials are shown as base material 18 in FIG. 1), and an upper cathode electrode 20 are sandwiched. Gaskets are typically used to seal the periphery of each electrode.

The improved internal electrolyte supply system illustrated in FIG. The hole 76 is connected to the hole 76. The supply system includes a series of first horizontal channels, each horizontally extending directly through one fuel cell between the bipolar brakes 12 and 14 to provide electrolyte to the matrix 18, as well as opposite opposite sides of the first horizontal channels. Electrolyte is supplied to the fuel cell assembly 58 along a series of second channels extending vertically through the assembly 58 adjacent the ends. The second channels are in fluid communication with the first channels and are adapted to supply electrolyte directly to the respective first channels.

More specifically, the bipolar plates 12 and 14 of the assembly 58 shown in FIG. 3 are provided with two pairs of double electrolyte flow grooves, a primary groove 78A and a secondary groove 78B as shown in FIG. and has. Auxiliary groove 78B is the main groove 78A
and connected to the main groove 78A by a series of spaced cross-flow channels 82 extending generally parallel to and defined in spaced relation within the plates 12 and 14 by an intermediate wall 92, between which the electrolyte flows. communicate with each other. The main groove 78A is also covered by a gasket. Furthermore, each auxiliary groove 78B is provided with an electrolyte transport wick 94 (only one of which is shown in FIG. 4), which engages the base material 18 and causes the base material 18 to In support of n
2 assists in the transfer of electrolyte to the material 18.

Inside the bipolar plates 12.14 of the aggregate 58 there are means for supplying electrolyte vertically downwardly through the aggregate into the main groove 78A by means of a bypass so that the electrolyte is supplied in succession one after the other. is provided. This means extends through the bipolar plates 12 and 14 of the battery in aligned relation in the direction of pitching force with respect to the opposite ends of the auxiliary groove 78B and spaced outwardly from the auxiliary groove to the opposite ends of the main groove 78A. The zero step section comprises an electrolyte channel 80 in spaced communication with the section, and a dam or step fi 88 defined between each electrolyte channel 80 of the plate and the main groove 78A.
A cascading flow of electrolyte is formed between channel 80 and main groove 78B to ensure a communicating channel.

Last but not least, the upper cooling plate 84 has a passage 80 at the left end, and the groove 78A, passage 80, and step 88 at the right end, whereas the lower cooling plate 85 has a passage 80 at the left and right ends. It only has a passage 80.

Because the step 88 offsets the position of the main groove 78A and the passageway 88, a bypass-type arrangement is created in which a small electrolyte pool is formed in the grooves 78A and 78B of each bipolar plate 12.14, and the pooled electrolyte is transferred to the next overflow onto the plate. With this configuration, there is no head pressure in the electrolyte flow.

As long as a mechanism is provided to easily supply a sufficient amount of electrolyte to the edges of the base material 18,
The details of the mechanism for feeding the edges of the 8 are not considered to be critical features of the invention.

The present invention provides significant advantages over the prior art by using a matrix with sufficient porosity to permit assembly of a fuel cell assembly prior to filling with electrolyte. Dry assembly results in labor savings. Furthermore, no dry chamber is required for acid concentration control during dry assembly or during acid filling.

In conventional methods, if too much acid is required or the acid distribution is poor before compaction of the aggregate,
Because lateral transport is extremely poor and the matrix lacks the ability to easily push excess acid from the edges of the cell into the electrolyte channel, the static pressure created by compaction of the aggregate is
According to the present invention, since the base material 18 is porous, the above problem is avoided.

A similar problem occurs due to the volumetric expansion of the acid caused by activation. Because the matrix 18 of the present invention is highly porous, the acid expands laterally and easily enters the electrolyte grooves, causing cell damage. The generation of lateral static pressure can be avoided.

Finally, the dry battery configuration allows the assemblage to be stored for any desired period of time using conventional storage techniques.

These advantages and disadvantages, such as not having to tightly control the environment as in prior art assemblies, reduce manufacturing and storage costs and increase the marketability of fuel cell technology.

One property of the matrix 118 that is sacrificed by the use of a high porosity matrix is the matrix's ability to withstand high pressure differentials (bubble pressure). 0.35k depending on system design
A pressure difference of 5 psi is required. However, when filled with acid, the silicon carbide layer 24 has a pressure difference of about 0.
It can handle a pressure difference of 58 kg/c (8 psi). Therefore, one advantage of the present invention can be exhibited without detracting from other desirable properties of the base material 18.

Although the invention has been described in terms of illustrative embodiments, many modifications and variations will be apparent to those skilled in the art. This includes all modifications and changes to the above.

[Brief explanation of the drawing]

FIG. 1 is an exploded view of a fuel cell. FIG. 2 is a diagram showing various passages inside the fuel cell shown in FIG. 1. FIG. 3 is a diagram showing a fuel cell assembly that is a preferred embodiment of the present invention. FIG. 4 is a plan view of the top surface of one of the bipolar plates of the assembly shown in FIG. 3 on the anode side. 10 Fuel cell 12.14 Bipolar plate 16 7 node electrode 18 FF1 material 20 Cathode electrode 22 Paper layer 78A Main groove 78B Auxiliary groove 80.82 Passage application Person: Westinghouse Electric Corporation

Claims (5)

[Claims] (1) A first plate and a second plate facing each other, a pair of opposing electrodes located between the first plate and the second plate, and a base material means located between the pair of electrodes. a fuel cell assembly comprising: disposed in said base material means a paper having sufficient porosity to permit assembly of the fuel cell prior to addition of an electrolyte; 1. A fuel cell assembly comprising a passage for supplying. (2) The fuel cell assembly according to claim 1, wherein the paper comprises a sheet of TORAY TGP 30. (3) The fuel cell assembly according to claim (1), wherein the base material is made of a silicon carbide layer. (4) The fuel cell assembly according to claim 1, wherein the passage supplies the electrolyte to an edge of the base material. (5) a) positioning a first electrode on a plate; b) disposing a high-porosity matrix having porous paper on the first electrode; and c) disposing a second electrode on the matrix. d) positioning a plate on the second electrode; and e) repeating steps a) to e) until a desired number of batteries are integrated.