JPH0325901B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a fuel cell, and particularly relates to a structure for simplifying the handling of a matrix in a unit fuel cell configuration and for replenishing electrolyte from the outside into a matrix layer. .

[Background of the invention]

Generally, the unit cells constituting the fuel cell are the first
As shown in the figure, the structure includes gas diffusion electrodes 1 and 2 having flow paths for fuel gas and air, and a matrix 3 arranged between the pair of gas diffusion electrodes. A battery body is constructed by stacking a plurality of unit batteries configured in this way with separators 4 interposed therebetween.

Therefore, conventional matrices are formed by adding phosphoric acid as an electrolyte to inorganic powder such as silicon carbide or metal phosphate, kneading the mixture, making a slurry, and applying the slurry to the gas diffusion electrode 1 or 2. If this is done, the matrix will protrude from the electrode due to battery tightening, etc., making it impossible to maintain the required amount of matrix, which will have an adverse effect on battery performance. For this reason, spacers are placed around the edges of the electrodes to prevent the matrix from protruding, but this is not perfect. In addition, since the matrix is a slurry made of strong acid mixed with concentrated phosphoric acid, it is important to know how to handle it during coating work and electrode bonding work.Furthermore, concentrated phosphoric acid has strong hygroscopicity, so the matrix slurry must be mixed with concentrated phosphoric acid. There are also problems in terms of quality control, such as how to store batteries after bonding electrodes, and measures against moisture absorption.

Another problem is that the electrolyte in the matrix is scattered and reduced to the outside together with the water (steam) generated by the battery reaction during battery operation, leading to a risk of deterioration of battery performance and shortening of battery life. Therefore, there is a method to reserve excess electrolyte in the gas diffusion part of the electrode, but with this method,
Diffusion of fuel gas and air is likely to be inhibited.
Furthermore, there is no good idea yet for how to replenish electrolytes from outside, and this method has not yet been put into practice.

[Object of the Invention] An object of the present invention is to simplify the matrix coating work and facilitate handling, provide a structure in which electrolyte can be supplied from the outside into the matrix layer, and improve and stabilize quality.

[Summary of the invention]

The fuel cell of the present invention is characterized in that the holding material for holding the electrolyte is a porous thin film in the form of a bag, the electrolyte is sealed inside the bag, and this is formed as a matrix layer. The point is that a replenishment port is provided within the layer.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 2, two porous thin films 6 are arranged, and a non-porous spacer 7 is arranged between the edges of the two films, and each of them is adhered. Further, a connecting pipe is provided at the end of the spacer 7 so as to pass through an electrolyte sealing port and a replenishing port 8 for replenishing electrolyte from the outside. In Figure 2, there are four electrolyte filling ports and replenishment ports.
In particular, there are no particular restrictions on the installation location or the number of people.
That is, as shown in FIG. 3, the electrolyte 3 sealed inside the porous thin film 6 passes through the pores of the thin film, reaches the electrode side, contacts the fuel gas and air, and a cell reaction occurs. By forming such a matrix layer, the matrix coating operation when assembling the unit cells involves placing a bag-shaped thin film on the electrodes, and applying the matrix at the time of stacking the unit cells or when the stacking of the main batteries is finished, for example. Since a set amount of electrolyte can be sealed by press-fitting using a quantitative dispensing device or the like, it is possible to work under the same conditions, making it easier to handle the matrix and stabilizing the quality.

Here, the amount of electrolyte to be sealed can be controlled by the pore diameter of the thin film to control the amount of electrolyte that permeates to the electrode side, so only phosphoric acid, which is the electrolyte, can be sealed. Further, even if a slurry impregnated with an electrolyte is enclosed in a powder which is a conventional matrix, there is no effect at all. Therefore, the pore diameter of the thin film mentioned above must be 40μ or less to cause wetting of the electrodes and prevent the battery reaction from being inhibited.
ml/cm ² /sec or more is desirable. In this way, even if an electrolyte is sealed inside a bag-shaped interior formed of a thin film, it will remain inside the thin film at normal pressure. Then, due to the battery clamping pressure, the electrolyte oozes out from the pores of the thin film and comes into contact with the reaction gas within the electrode as described above, causing a battery reaction. The material of this thin film is
Acid resistance and heat resistance are required. For example, fluorine resin PTFE (polytetrafluoroethylene resin)
The spacer 7 shown in FIG. 3 uses non-porous PTFE. By doing so, leakage of electrolyte from the edge portion of the matrix layer can be prevented.
Also, as the thickness of this porous thin film increases, the internal resistance of the battery increases, leading to a decrease in battery performance, so it is better to be as thin as possible, but when considering the strength of the thin film, it is preferably about 25 to 100μ. .

In FIG. 4, the electrolyte sealing port 9 described above is connected to an external electrolyte replenishing tank 10 via a manifold 5. By applying appropriate pressure to the external electrolyte tank at all times, the electrolyte will always be replenished inside the matrix tank, eliminating the loss of electrolyte scattering due to battery operation, and stabilizing battery performance and extending the lifespan. I can do it. By doing as in this embodiment, the matrix application work is simplified, and furthermore, the structure allows easy replenishment of electrolyte from the outside, thereby improving quality and stabilizing the structure.

〔Effect of the invention〕

According to the present invention, since the electrolyte is retained using a porous thin film, handling of the matrix becomes easy, and an electrolyte replenishment path can be easily constructed from outside the manifold.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a conventional battery, Fig. 2 is a perspective view of the structure of a matrix layer according to the present invention, Fig. 3 is a perspective view of the matrix of Fig. 1 configured into a unit battery, and Fig. 4 is a perspective view of the matrix layer. FIG. 6... Porous thin film, 7... Spacer, 8...
...Electrolyte sealing port, 9...Connection pipe.

Claims (1)

[Claims] 1. A matrix is sandwiched between a fuel electrode and an air electrode that have opposing gas flow paths, and a plurality of these are stacked up as unit cells with separators interposed therebetween, and fuel gas and air are placed on the sides of the cells. 1. A fuel cell equipped with a manifold for supplying and discharging the matrix, characterized in that the matrix is formed into a bag shape using a thin film, the thin film is made porous, and an electrolyte is sealed inside. 2. The fuel cell according to claim 1, wherein a replenishment port for the electrolyte is provided at a peripheral edge of the matrix formed of the porous thin film.