CS213400B2 - Method of making the metal and air current source - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a method for producing an indirect air (oxygen) cathode power source. In the last twenty years, research activity has developed considerably with the aim of creating air or oxygen electrodes for metal-air elements. During this research, two types of these electrodes have been produced: a) a hydrophilic type, the formation of which is described, for example, in United Kingdom Patent Nos. 1,113,043, 1,212,853, 1,167,178 and 1178,053, and U.S. Pat. 3 318 736 and 3 573 992. A common disadvantage of these electrodes is that they require a closed space and permanent overpressure to operate them; b) a hydrophobic type which has recently been expanded and which is described in U.S. Pat. Nos. 3,348,975 and 3,753,788; in Hungarian Patent Specification No. 159,822 and in United Kingdom Patent Nos. 1,159,344, 1,158,580, 1,272,109, 1,138,469 and 1,120,591; these patents disclose electrodes hydrophobic and fixed with Teflon. Other solutions of this kind in which the electrodes are made of activated carbon are disclosed in United Kingdom Patent Nos. 1158,580 and 1,246,830 and U.S. Patent Nos. 3,335,034 and 3,562,841.

The common feature of hydrophobic cathodes is that they do not need either auxiliary power or overpressure to operate. For both types of electrodes, there is a three-phase reaction zone (gas, liquid, solid) in which the reduction of oxygen contained in the air proceeds. Depending on the time of operation and the load, the zone moves in the direction of the air side of the electrode, changing its properties, thereby deteriorating the electrode's electrical parameters.

Another common drawback of said air cathodes is the leakage of electrolyte, which occurs partly in the pores of the electrodes, partly in the contact points.

Numerous attempts have already been made to eliminate these adverse phenomena, such as the deposition of an insulating polytetrafluoroethylene layer, as disclosed in U.S. Patent Nos. 3,348,975 and 3,370,508, as well as in United Kingdom Patent Nos. 1,272,109 and U.S. Pat. 1 138 469, but it has still not been possible to produce a completely leaking electrode. In the proposed solution according to the invention, the method of working the air (oxygen) cathode deviates considerably from the above-described solutions, while at the same time giving rise to leaking batteries with a time stable performance.

The operation of the air cathodes used so far using alkaline electrolytes can be schematically illustrated as follows. The oxygen diffusing through the cathode insulating layer reacts in the three-phase electrolyte catalyst zone

The OH-ions formed at the cathode enter the next reaction with the positive ions formed at the anode during charging (ionic association; for example, with H + to water). Accordingly, the cathode reaction proceeds only in the three-phase, ultra-thin interface, optionally depending on the low dissolution capacity of oxygen in the electrolyte-coated layer, whose activities and hydrophobes remain over time, thereby constantly moving the reaction zone and its lifetime. mezena.

The indirect cathode of the invention does not use oxygen from the air immediately, but works with oxygen in the dissolved electrolyte in advance so that instead of a three-phase zone (gas, liquid, solid) there is only a two-phase zone (liquid, solid).

The essence of the invention is that the oxygen or air cathode of the electric cell is completely immersed in an electrolyte having a solubility of at least 0.05 ml oxygen per ml electrolyte and 1 oxygen required to operate the electrolyte at room temperature and oxygen pressure of 0.128 MPa. it dispenses physically or physically-chemically dissolved and during operation continuously replaced oxygen, optionally from air. This reduces the corrosion of the cathode, giving the possibility of generating a power source with a lifetime of several tens of thousands of hours, which will not suffer any damage even if it remains out of service.

The process of the invention will be explained in more detail with reference to the drawing, which illustrates a method for producing a metal and air flow source according to the invention. The anode 1 and the cathode 2, which are submerged in the electrolyte 3, are arranged in the body 5. The nozzle 4 feeds the electrolyte into the electrolyte, which is dissolved in the electrolyte by physical or physical-chemical means. When the oxygen-saturated electrolyte reaches cathode 2, the dissolved oxygen enters the electrode into the electrochemical reaction, forming hydroxonium ions, whereupon the electrode reactions proceed in the usual manner.

This reaction process cannot in any way take place in the usual electrolyte due to the extremely slow course, since its oxygen dissolution capacity (about 0.0005 ml of Oa / ml bath) is in excess of the desired value (0.05-0.5 ml O 2 / ml bath ) is disproportionately lower.

Accordingly, an electrolyte is used in which the solubility of oxygen is at least one order of magnitude greater than that of the commonly used alkaline electrolytes.

Compounds which dissolve relatively high levels of oxygen are, for example, perfluoro compounds such as perfluoro-2-butyl tetrahydrofuran, ethers such as dibutyl ether, oxo compounds such as methyl, ethyl ketone and alcohols such as ethanol, methanol and also organic acids such as formic acid. The dissolution ability of n oxygen can be quantified by

nteraiiu uuuuuia uujjwnua áiuuua the blood oxygenation capacity of hemoglobin and is about twenty times higher than that of water and about a hundred times higher than the dissolution ability of 30% KOH. In the production of the electrolyte, these polar or non-polar solvents are electrically dissociated in a manner known per se by dissolving organic or inorganic dissociating substances. Oxygen-dissolving electrolytes may be used unmixed, or mixed with one another, and may account for 1 to 99% of the total volume. The catalysts used may be silver, silver and mercury compounds, or organic iron and cobalt compounds, for example phthalocyanides, which are used in the production of oxygen electrodes. The advantages of the solution used are as follows: 1. Since there is no need for a separate separate gas space, the anodes and cathodes can be arranged in a common solid wall body, thereby eliminating the risk of leakage. 2. The oxygen-saturated electrolyte comes into contact with the entire electrode surface, whereby the reduction of oxygen is not limited to a thin three-phase layer, and there is no need to create a high local current density causing corrosion of the electrodes. Thus, neither the shifting of the reaction zone nor the limitation of the function of the electrode takes place. 3. There is no need to adjust the overpressure and use an airtight seal. A single, low-power fan is sufficient to vent all cells. 4. As the anode, a metal electrode (e.g., zinc, cadmium) may be used as a metal, air and current source; For gas or liquid electrodes (eg water, methanol) a heating element must be installed. Example 1

50 g of silver powder (grain size less than 40 µm), 8 g of PVC powder (grain size less than 20 µm) and 10 ml of distilled water were mixed. The mixture was triturated onto a 10 µm nickel screen. the content of silver in the layer on the sieve was 5 mg / cm 2. The sieve was dried at room temperature and then subjected to a heat treatment at 250 ° C for 15 minutes. The electrolyte mixture was prepared by dissolving 10 g of lithium perchlorate in 50 ml of perfluoro-2-butyltetrahydrofuran. The produced electrode was immersed in a bath, as a zinc electrode made in a manner known per se was used as an anode. Between the anode and the cathode, 8 x 10 -4 m polyamide separators were inserted to separate the oxygen. After the introduction of air or oxygen into the bath, the battery is available and the cathode current density value exceeds 15 mA / cm 2.

These tests were carried out in 100 cycles, ie for 500 discharging and 1000 charging hours, the terminal voltage was IV, there were no harmful deposits at the cathode. EXAMPLE 2 50 g of cobalt phthalocyanide were mixed with 20 g of polyethylene powder and 30 ml of water, then the mixture was spread on a nickel sieve (fiber thickness 60 [mu] m, mesh length 120 [mu] m so that the catalyst was 50 mg / cm2 on the electrode surface. was dried and subjected to a heat treatment at 230 ° C for 20 minutes The electrode produced was immersed in the electrolyte described in Example 1 and tested under the conditions also given in Examples 1. The current density obtained was 8 mA / / cm 2 at terminal voltage 1 V.

Claims (1)

Original document published without claims.