JPH01307172A - Electrolyte refilling device for matrix type fuel battery - Google Patents

Abstract

PURPOSE:To supply electrolyte uniformly independently from varying fluid resistance by furnishing an electrolyte refilling trough separately from a fuel battery, and supplying the electrolyte pressurized to a pressure some higher than the reactive gas pressure through an electrolyte refilling pipe divergently to the electrolyte storing part of each unitary cell. CONSTITUTION:An electrolyte refilling device according to existing invention consists of an electrolyte refilling trough 21, which contains electrolyte and is equipped with a pressurizing means 30 to press the liquid surface with a certain pressure, a mother pipe 23 whose one end opens in the electrolyte contained in this refilling trough 21, and a branch pipe 24 which diverges from this mother pipe 23 and whose other end is in communication with the electrolyte storing part 3d of each unitary cell 1. The specified pressure to be applied to the mentioned refilling trough 21 shall be some higher than the pressure of reaction gas supplied to the battery lamination 10, and the electrolyte extruded into the abovementioned mother pipe 23 is supplied distributedly to the electrolyte storing parts 3d through the branch pipe 24. This enables certain refill of the electrolyte even though the fluid resistance in the electrolyte refilling path 22 of the battery 1 has varied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrolyte replenishing device for a matrix fuel cell, which is formed by stacking a plurality of unit cells each including a porous matrix layer as an electrolyte holder.

[Conventional technology]

In the aforementioned matrix type fuel cell, a fuel gas electrode, such as a hydrogen electrode, which is supplied with fuel gas and maintains the anode reaction, and a fuel gas electrode, which is supplied with oxidizing gas, are sandwiched between a matrix layer that serves as a porous insulating layer that holds an electrolyte. An oxidizing gas electrode, such as an air electrode, is arranged to maintain the cathodic reaction. These constitute a unit cell as one power generation element, but in order to continuously supply the reactant gas, that is, the fuel gas and the oxidizing gas to the fuel and oxidizing electrodes mentioned above, one
Either cut a groove in the i8i itself to allow the reaction gas to flow through it, or
When a plurality of unit cells are stacked, a groove is provided in a separator plate interposed between the unit cells to partition the fuel gas section and the oxidizing gas section. The former will be referred to as a grooved electrode structure, and the latter will be referred to as a grooved separator plate structure.

On the other hand, for the electrolyte dissolved in the electrolytic solution or the electrolyte used as the electrolytic solution, a substance 1, for example, phosphoric acid, which causes less chemical change in -m and less damage due to evaporation etc. is used. During long-term operation of a battery, it is unavoidable that electrolyte is lost from the battery, albeit in small amounts, and some means must be taken to replenish the electrolyte or electrolyte.

In order to replenish the matrix with electrolyte that is gradually lost, an electrolyte reservoir is often provided within the cell or its 41 layers to store the electrolyte. For example, in the case of the above-mentioned grooved electrode structure, this electrolyte reservoir is located within the electrode.
In the case of temporary separator structure with 11, on the separator plate,
They are formed by locally imparting electrolyte retention and permeability, respectively.

[Problem to be solved by the invention]

Since the electrolyte storage section described above must be provided within a limited space within the battery, there is a limit to the amount of electrolyte that can be stored, and in the case of a grooved electrode structure, the electrode is made of a porous material. There is a disadvantage that the gas diffusion function of the gas is more or less inhibited by the provision of the storage section.

In order to solve the problem of electrolyte replenishment, it is necessary to overcome the above-mentioned drawbacks and to develop an electrolyte replenishment device that satisfies the following requirements.

fal If the electrolyte supply path to each cell is common, a so-called liquid junction is created between the cells through the electrolyte.

(bl) When operating a battery for a long period of time, it is necessary to prevent leakage from the electrolyte supply path.

fc) The viscosity of the electrolyte tends to change considerably when the temperature changes, and if air bubbles are mixed into the electrolyte, the apparent viscosity or fluid resistance will change, so even if the fluid resistance changes slightly, the electrolyte can be replenished reliably. Must be able to do it.

In particular, item (C) is important when trying to reduce the external dimensions of the battery stack by making the electrodes or separator plates as thin as possible.
Since the cross-sectional area of the electrolyte replenishment path is naturally reduced accordingly, this is a factor that poses a considerable hindrance to the development of a highly reliable electrolyte replenishment device.

An object of the present invention is to overcome the above-mentioned problems and to provide an electrolyte replenishment solution for a matrix fuel cell that can reliably replenish the electrolyte even if the fluid resistance in the electrolyte replenishment path inside the battery changes.
The equipment is to be obtained.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, there is provided a porous matrix layer as an electrolyte holding body, and an electrolyte storage part formed in the longitudinal direction so as to communicate with the matrix layer and having electrolyte holding property. A device for replenishing electrolyte to a battery stack consisting of a plurality of stacked single cells each having an electrolyte replenisher comprising a pressurized container separated from the battery stack and having pressurizing means. An electrolytic cell comprising a tank, a main pipe part with one end opened into the electrolyte stored in the electrolyte supply tank, and a plurality of branch pipe parts branched from the main pipe part and the other ends communicating with the electrolyte storage part. The fuel cell is provided with a liquid supply pipe and a means for discharging the remaining electrolyte in the main pipe portion to the outside of the fuel cell.

[Effect]

In the above means, there is provided an electrolyte replenishment tank that contains an electrolyte and is equipped with a pressurizing means for pressurizing the liquid surface at a predetermined pressure, a main pipe portion with one end opened into the stored electrolyte of the replenishment tank, and By providing a branch pipe section which branches off from the main pipe section and whose other end communicates with the electrolyte storage section of each unit cell, the predetermined pressure applied to the replenishment tank can be controlled from the pressure of the reaction gas supplied to the battery stack. By increasing the height somewhat, the electrolytic solution pushed into the main tube can be distributed and supplied to each electrolytic solution storage section via the branch tube.

In addition, by providing a means to discharge the remaining electrolyte in the electrolyte replenishment tube, it is possible to replenish the electrolyte while the fuel cell is stopped and to remove the electrolyte in the replenishment tube during operation. This makes it possible to easily avoid liquid junctions during operation.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a structural diagram showing the overall configuration of an apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view showing the main parts of FIG. 1, showing the detailed structure of the electrolyte storage section. In Figure 1,
IO is a battery stack, in which a plurality of single cells 1 and separator plates 5 made of gas-impermeable carbon plates are alternately stacked, and are integrally formed by applying a predetermined surface pressure to the stacked surfaces. Ru. Each cell 1 has a matrix layer 2
, a fuel gas electrode 3 , and an oxidizing gas electrode 4 . Furthermore, each electrode 3.4 is an electrode substrate 3a.

4a and catalyst layers 3b, 4b, and each electrode substrate 3a, 4a has grooves 3c, 4c for reaction gas on the surface opposite to the matrix layer 2, respectively. As is well known, the groove 4C of the electrode substrate 4a is cut in a direction perpendicular to $3c of the electrode substrate 3a on the fuel gas side. These unit cells 1 are stacked together with a gasket 6 disposed on the periphery with an airtight separator plate 5 interposed therebetween to form the above-mentioned battery stack 10.

On the other hand, 21 is a replenishment tank for electrolyte solution (phosphoric acid solution) 20,
In addition to storing a sufficient amount of electrolyte necessary for replenishment, a pressurizing means 3 using, for example, an inert gas 33 as a pressurized gas is used.
0 and pressure tube 31. Further, since the replenishment tank 21 requires corrosion resistance against the electrolyte 20, for example, tetrafluoroethylene (trade name: Teflon) is suitable for the phosphoric acid electrolyte. 22 is an electrolyte replenishment pipe (hereinafter abbreviated as replenishment pipe); A main pipe section 23 that opens into the electrolytic solution 20, passes through the replenishment tank airtightly through a backing 44, and is drawn out to the outside, and the other end is opened to the atmosphere via a valve 42; and a main pipe section 23 that branches from the main pipe section 23. The other end of the fuel gas electrode substrate 3a of each unit cell 1 is composed of a plurality of branch pipe portions 24 which are connected to the electrolytic cell 1/& and supply/1!13e formed on the fuel gas electrode substrate 3a of each unit cell 1.

In addition, since it is necessary to replenish a predetermined amount of electrolyte to each cell equally, the hole where the main pipe part 23 and branch pipe part 24 communicate is opened in a different area for each cell, and inside each branch pipe. It is necessary to equalize the electrolyte replenishment flow rate between the cells due to the pressure loss of the electrolyte passing through the cell.

Furthermore, since multiple cells are connected by the electrolyte supply main pipe and branch pipes, at least one of the electrolyte supply main pipe or branch pipes is made of an insulating tube such as a Teflon tube to prevent liquid leakage between the cells. be done. Further, after replenishment is completed, at least no electrolyte should remain in the replenishment main pipe. Therefore, an electrolyte discharge means consisting of a valve 42 arranged on the outlet side of the main pipe section 23 and an intake cock 41 arranged on the inlet side thereof is provided, and the remaining electrolyte in the main pipe section is removed during power generation operation of the fuel cell. is discharged toward the receiver 43.

On the other hand, as shown in the perspective view of the second tooth of the electrode substrate 3a of the fuel gas electrode 3, a plurality of fuel gas a3c are formed in parallel to each other in contact with the separator plate 5, and one end is parallel to the groove 3c. An electrolyte replenishment groove 3e with a dead end is formed. The end of the branch pipe part 24 branched from the main pipe part 23 is fitted into one end of the supply groove 3e, and the opening part 24a is connected to the a3
Connects to e.

Since the electrode base material 3a is composed of a gas diffusion material 1, for example, a porous graphite material, the electrode base material 3a is generally impregnated with a liquid-repellent Teflon-based material, etc. Measures are taken to prevent leakage to the outside. 3d is a storage part for the electrolytic solution 20, and the electrolyte Bi1 base material 3
By not performing the In solution treatment by infiltrating the Teflon material only in the limited portion surrounding the groove 3e of a, a reservoir having electrolyte retention and permeability is formed. Further, as shown in FIG. 1, the electrode catalyst layer 3b supported on the back side of the electrode base material 3a is formed with communication holes 3f for electrolyte in a distributed manner. The electrolyte accumulated in the main pipe part 23. communicates with the matrix 2 through the communication hole 3f, and the branch pipe part fitted in the groove 3e is somewhat crushed so that the groove 3e forms an electrolyte chamber, so that the main pipe part 23. Branch pipe section 24. An electrolyte supply passage consisting of a groove 3e, a storage section 3d, and a communication hole 3f is formed.

Therefore, if a predetermined pressure is applied to the liquid level of the contained electrolyte 20 in the supply tank 21 by the pressurizing means 30, and the valve 42 is opened to expel the gas in the main pipe part 23 and then the valve 42 is closed, the electrolyte 20 is connected to the groove 3 of each jIL battery l via each branch pipe part 24.
e, permeates into the storage section 3d, and is supplied to the matrix via the communication hole 3f. At this time, the electrolyte in the supply passage is supplied while being energized to a pressure higher than the reaction gas pressure in the battery by a predetermined value. Even if there are slight changes due to contamination, etc., replenishment will be ensured. Furthermore, in order to prevent the electrolytic solution supplied to the branch pipe section 24 from returning when draining the remaining electrolyte in the main pipe section 23 to prevent a liquid junction during power generation operation, the main pipe section 23 and the branch pipe section 24 should be It is preferable that the height position of the branch part is higher than the height position of the corresponding groove 3e, and by doing so, air bubbles that have entered the branch pipe part 24 can be discharged to the main pipe part side. This makes it possible to prevent blockage of the branch pipe portion or increase in fluid resistance due to air bubbles.

〔Effect of the invention〕

As described above, this invention provides an electrolyte replenishment tank having a pressurizing means separately from the fuel cell, and applies a pressure somewhat higher than the reaction gas pressure via an electrolyte replenishment pipe consisting of a main pipe and a branch pipe. The pressurized electrolyte was configured to be branched and supplied to the electrolyte storage section of each unit cell. As a result, the electrolyte can be evenly supplied to each cell without being affected by changes in the viscosity of the electrolyte or changes in fluid resistance due to the inclusion of air bubbles. When discharging the electrolyte through the discharge means, it is possible to prevent the electrolyte supplied to the branch pipe from backflowing, making it possible to alternately and repeatedly supply and discharge the electrolyte, ensuring liquid junction. can be prevented. Further, since the electrolyte replenishment tank is housed in a pressurized container with a closed structure necessary for pressurization, completely isolated from the reaction gas, the possibility of troubles caused by electrolyte leakage can be extremely reduced.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram including a sectional view of a fuel cell stack showing a device according to an embodiment of the present invention, and FIG. 2 is a perspective view showing essential parts of the device according to the embodiment. 1: Cell, 2: Matrix, 3: Fuel gas electrode, 4
Dioxide gas electrode, 5: separator plate, 10: battery stack, 3d: electrolyte storage section, 3e: electrolyte supply tank, 3f:
Electrolyte communication hole, 20; Electrolyte, 21; Electrolyte supply: ★,
22: Electrolyte supply pipe, 23: Main pipe part, 24; Branch pipe part, 3
0: Pressurizing means, 41.42: Valve (electrolyte solution!) L outlet means), 33: Pressurizing gas. Substitute! Patent Attorney Iwao Yamaguchi Hatakeno-ton Figure 2

Claims (1)

[Claims] 1) A porous matrix layer as an electrolyte holder;
This device replenishes electrolyte to a battery stack formed by stacking a plurality of unit cells, each of which has an internal electrolyte reservoir formed in the longitudinal direction so as to communicate with the matrix layer and capable of retaining electrolyte. An electrolyte replenishment tank comprising a pressurized container separated from the battery stack and having a pressurizing means, a main tube portion with one end opened into the electrolyte contained in the electrolyte replenishment tank, and this main tube. and a means for discharging the remaining electrolyte in the main pipe part to the outside of the fuel cell. An electrolyte replenishment device for matrix-type fuel cells characterized by: