JPS60115171A - Liquid fuel cell - Google Patents

Abstract

PURPOSE:To obtain a small light liquid-fuel cell having a high output and a high energy density by providing an arborescent fuel path having a primary path and branching paths in the negative electrode and supplying a fuel through the main path. CONSTITUTION:On the upper surface of a negative electrode 3, a fuel inlet 9 is provided from which arborescent paths extend into the negative electrode 3. The arborescent paths consist of a primary path 10, secondary paths 11, branching paths 12 and tertiary-branching paths 13. A liquid fuel supplied through the fuel inlet 9 passes through these paths before being homogeneously supplied over the entire surface of the negative electrode 3. The surface area of the cross section of each path extending from the primary path 10 to the tertiary-branching path 13 may continuously vary. By the means mentioned above, the fuel can be supplied directly into the negative electrode 3 and can easily reach the electrolyte- side surface of the negative electrode 3. Furthermore, the fuel moves toward electrolyte-side surface of the negative electrode 3 in arborescent form and diffuses over the entire surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to liquid fuel cells, and more particularly to a compact, high-performance liquid fuel cell.

A cross-sectional view of a conventional liquid fuel cell is shown in FIG.

A positive electrode 2 and a negative electrode 3 face each other with an electrolytic solution 1 in between, and an oxidizer chamber 4 is located outside the positive electrode 2, and a fuel chamber 5 is located outside the negative electrode 3. An oxidant supply port 6 and an oxidant discharge lower are installed in the oxidizer chamber 4, and a fuel supply port 8 is installed in the fuel chamber 5. Both the positive electrode 2 and the negative electrode 3 have electron conductivity. It is a porous body with material strength of 1.

Liquid fuel cells are expected to be used as portable power sources, and for this purpose they must be as small and lightweight as possible. In other words, regarding the output W, W/kg e
W/di”s W h/kg + W h
/ dm" value must be large. However, in conventional liquid fuel cells, in order to quickly and evenly supply liquid fuel to the entire surface of the negative electrode, the fuel chamber must be sufficiently wide, and the The weight and volume increase, so the above W / kg e W / dIla * W h
/ kg *Wh/dm" value was large, which hindered full-scale practical application.

In addition, the reaction in the negative electrode No. 3 of a fuel cell proceeds on the surface of the negative electrode on the electrolyte side, that is, the surface close to the positive electrode, but in conventional negative electrodes, fuel enters from the surface of the negative electrode on the fuel chamber side and becomes porous. It was necessary to cross the inside of the negative electrode to reach the surface where the reaction easily progresses. For this reason, insufficient fuel supply to the reaction surface was likely to occur, and the current density, that is, the value of the extracted current divided by the apparent electrode area, was also small.

An object of the present invention is to provide a small, lightweight, high output, and high energy density liquid fuel cell that allows fuel to easily reach the surface of the negative electrode on the electrolyte side.

The key point of the present invention is that a liquid fuel supply passage is provided within the negative electrode. That is, a dendritic fuel passage having a main path and branch paths is provided in the negative electrode, and fuel is supplied through the main path.

Hereinafter, the present invention will be explained in more detail with reference to the drawings. FIG. 2 is a longitudinal cross-sectional view of the negative electrode 3 used in the liquid fuel cell according to the present invention, that is, a cross-sectional view in a direction parallel to the surface of the negative electrode 3;
The figure is a cross-sectional view taken along the line AA of the negative electrode 3, that is, a cross-sectional view taken in a direction perpendicular to the surface of the negative electrode 3.

There is a fuel population 9 on the top surface of the negative electrode 3, and from that point,
A dendritic passage is provided in the negative electrode 3 and extends therethrough.

The dendritic passages include a main trunk passage 10, a growing trunk passage 11, a branch trunk passage 12,
It consists of narrow passages 13, through which the liquid fuel supplied from the fuel port 9 is uniformly supplied over the entire surface of the negative electrode. Of course, the passage cross-sectional area from the main passage 10 to the narrow passage 13 may change continuously.

The liquid fuel used is methanol, hydrazine, or a mixture of these and other liquid fuels. By doing so, the fuel can be directly supplied into the negative electrode, making it easier to reach the surface on the electrolyte side. Moreover, the fuel progresses in a dendritic manner toward the electrolyte side of the negative electrode and spreads over the metal surface area.

The present invention will be explained in detail below. A positive electrode made by mixing carbon powder added with a platinum catalyst and polytetrafluoroethylene fine powder and coating it on a porous carbon substrate, an ion exchange membrane impregnated with sulfuric acid as an electrolyte, and a dendritic passageway inside. A battery was assembled by combining a negative electrode made of a porous carbon plate with a negative electrode, and the positive electrode was supplied with air, and the negative electrode was supplied with a mixture of methanol and sulfuric acid as fuel to operate as a methanol-air fuel cell. Platinum was also dispersed and added to the negative electrode as a catalyst. When the electrode dimensions are 10 cm x l 5 cm, the width of the air chamber is 3.0 mm, and the thickness of the air electrode is 0.3 mm.
ll1m, the thickness of the ion exchange membrane impregnated with electrolyte is 0
．． The thickness of the negative electrode was 2.0 mm, and the thickness of the fuel chamber was OI. Therefore, the thickness of one unit battery is 5.
5 am, and if we ignore the surrounding frames, the volume is 8
It is 2.5 cm3. Similarly, excluding the surrounding frame, etc., the weight at this time was 90.7 g.

A current of 18 A was obtained from this unit cell at a discharge voltage of 0.40 V. The current density is 120 mA/Cn12. Therefore, the output power of this unit battery is 7.2 W, the output per unit volume is 87.3 W/β, and the output per unit weight is 79.4 W/kg. In this way, the present invention does not require a fuel chamber, and the output per unit volume or unit weight also increases.

On the other hand, in a battery with a conventional structure, when the electrode dimensions are set to 10 cm x 15 cm, which is the same as in the embodiment of the present invention, the width of the air chamber is 3.5 cm. , Omm, the thickness of the air electrode is 0.3 mm, the thickness of the ion exchange membrane impregnated with electrolyte is 0.2 mm,
Although the thickness of the negative electrode remains the same at 2.0 mm, a space of 3.0 mm width must be reserved for the fuel chamber, and the thickness of the unit cell is 8.5 nm+m, ignoring the surrounding frame etc. The volume of the unit battery at this time is 127.5 cm''.

The weight at this time is 145g. With this unit battery, a current of 15 A was obtained at a discharge voltage of 0.40 V. The current density is 100mA/cm''. Therefore, the output of this unit cell using the conventional method is 6.OW, the output per unit volume is 47.OW/Q, and the output per unit weight is 41.OW. It is 4W/kg.

Comparing the battery of the present invention with a conventional battery, the battery of the present invention has 1.86 times higher output per unit volume and 1.92 times higher output per unit weight.

As described above, according to the present invention, by reducing the fuel chamber space and improving cell performance, the output per unit volume and output per unit weight are significantly increased compared to conventional liquid fuel cells. do.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional liquid fuel cell, FIG. 2 is a sectional view of an embodiment of the present invention, and FIG. 3 is a sectional view taken along line AA in FIG. 1... Electrolyte, 2... Positive electrode, 7... Negative electrode, 4...
・Oxidizer chamber, butt...Fuel chamber, 6...Oxidizer supply port, 7
... Oxidizer discharge port, 8... Fuel supply port. 1st item 2nd figure

Claims (1)

[Claims] (2) A liquid fuel cell characterized in that fuel is supplied through the opposing positive and negative electrodes, an electrolytic solution interposed between the positive and negative electrodes, an oxidizer reservoir located outside the positive electrode, and the main path.