FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a chemical current source and

storage batteries and, more particularly, to methods of preparing water-

activated batteries with soluble anodes of a chemical current source and

storage batteries.

Many chemical current sources are known. These differ in their

dimensions, in their manner of construction and in the nature of the

electrochemical reactions which take place in the sources. The current

sources also vary in their use-related properties, such as, for example, their

applicability to underwater or above-water devices, rescue and signaling

equipment, electric vehicles, and the like.

It is common to intensify the reactions taking place at the electrodes

of a chemical current source by making use of various metallic alloys for

the fabrication of the negative electrode (anode).

Chemical current sources can be described and rated in terms of

various performance indicators, such as their energy density, their capacity,

and their internal resistance per unit area of electrode surface or per unit

mass or per unit volume of the cell.

Additional considerations are cost and availability of the materials

needed for the construction of the electrodes, and the service life and shelf-

life of the current source, as well as the ecological effects of its production,

use and discarding.

The active portions of the electrodes may, in theory, be made of any

of a large variety of metalloids, including those which are aluminum and

magnesium based. Based on energy density consideration, the choice is

usually limited to metalloids which include lead, nickel, cadmium, iron,

manganese, zinc, lithium, silver, alone or in combination.

There have been attempts to produce chemical current sources with

electrodes of aluminum and magnesium, but these attempts have not found

wide application due to their inherent shortcoming of the high resistivity

of the protective oxide layer which tends to form around the anode and

which leads to a potential barrier of about 1 volt. This potential barrier,

in turn, produces a highly negative differential effect which increases the

corrosion current and increases of the anodic current density.

It is largely this limitation which has tended to rule out the use in

chemical current source anodes of aluminum alloyed with rare metals, such

as indium, thallium and gallium. Other considerations, such as the high

cost and relatively high toxicity, also played a role.

A further shortcoming of known water-activated chemical current

sources, and of air-magnesium cells in particular, is their inability to

operate intermittently. This is caused by the high self-discharge and the

corrosion of the anode, which is permanently activated following its initial

operation.

There is thus a widely recognized need for, and it would be highly

advantageous to have, an inexpensive and long-lasting chemical current

source, capable of generating a large current density over a long period,

including in intermittent use.

SUMMARY OF THE INVENTION

According to the present invention there is provided a method of

making material for use in fabricating an anode for use in a chemical

current source, comprising: (a) heating a mixture including aluminum and

magnesium to at least the fusion point of the mixture in the presence of

hydrogen to form a molten mass; and (b) cooling the molten mass to form

the anode material, and an anode made in this way.

Also according to the present invention there is provided a method

of making material for use in fabricating an anode for use in a storage

battery, comprising: (a) heating a mixture including aluminum and

magnesium to at least the fusion point of the mixture in the presence of

hydrogen to form a molten mass; and (b) cooling the molten mass to form

the anode material, and an anode made in this way.

According to further features in preferred embodiments of the

invention described below,

According to still further features in the described preferred

embodiments, the mixture used to fabricate an anode for use in a chemical

current source further includes solder, potassium hydroxide, nitride of

nickel, nitride of zinc, or nitride of titanium, or combinations thereof. A

mixture used to fabricated an anode for use in a storage battery is further

made up of nickel hydroxide.

An anode according to the present invention can be used, along with

a cathode and an electrolyte, to form a chemical current source, which

preferably features means for heating the anode.

Anodes according to the present invention can be used, along with

appropriate cathodes electrolytes, to form an energy plant which includes

a chemical current source and an electrically connected storage battery.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with

reference to the accompanying drawing, which schematically depicts an

energy plant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of a method of fabricating an anode and of

an anode, for use in chemical current sources and in storage batteries.

The present invention addresses the task of improving the

performance characteristics of chemical current sources by making use of

a water-activated negative electrode (anode) made of a magnesium-

aluminum alloy impregnated with hydrogen. The magnesium-aluminum

is brought to the molten state under an atmosphere of hydrogen, in the

presence of one or more additives which facilitate the impregnation of the

melt by hydrogen.

To fabricate an anode according to the present invention, magnesium

and aluminum granules are mixed one or more additives, such as granules

of solder, granules of potassium hydroxide, powdered nitrides of nickel,

zinc and titanium, and the like. Any suitable proportions may be used.

Preferably, the magnesium, aluminum, solder, potassium hydroxide, nitrides

of nickel, nitrides of zinc and nitrides of are in the following mass-

proportions: 7-52%, 38-84%, 2-4%, 0.5-1.5%, 0.5-1.5%, 3-5% and 1-4%,

respectively.

The mixture is heated under hydrogen atmosphere, to above the

melting temperature, so as to form a molten mass. The melt is

subsequently cooled or allowed to cool and harden to some suitable

temperature, forming the anode material. Preferably the cooling takes

place in molds which are shaped and sized so as to result in a finished

anode after cooling.

Without in any way limiting the scope of the present invention, it

is believed that these operations result in the formation of solid solutions

and compounds. The resultant anode possesses higher electrochemical

activity.

Without in any way limiting the scope of the present invention, it

is believed that the heat treatment of the aluminum/magnesium alloy at the

liquefying point under hydrogen, at adequate pressure, affects the electronic

state and modifies the structural parameters of the aluminum and of the

magnesium initiating the penetration into their crystalline lattice of

hydrogen atoms, that is, of protons, which are all bound in a medium

replete with free electrons. The number of electrons at the bound level

may be two, that is, hydrogen plus whatever ion forms an H ^' , which causes

less anode metal polarization and heightens the resistance to corrosion,

typically be a factor of 2, on account of the higher toughness due to

intensive hydrogen penetration into the metal surface, which passivates it.

The formation of the H ^" ion causes a shift of the potential of the

chemical current source at the magnesium/aluminum anode, without the

formation or release of any toxic admixtures. The resultant anode has

increased resistance to electrochemical corrosion.

The discharge current density is capable of instantaneously reaching

from 2 to 500 milliamperes/cm.sq., and higher.

The higher stability of magnesiunValuminum alloys and the reduced

corrosion due to the negative differential effect testify to the effect which

passivation has at relatively low current densities and chemical current

source self-discharge. The increased corrosion resistance throughout the

anode volume is therefore practically realized by the anode reagent all over

the magnesium-aluminum electrode volume. The working under hydrogen

also has a beneficial influence on the electrochemical activity of the

resultant intermetallic compounds of aluminum-magnesium-tin-lead-zinc-

nickel.

The method for fabrication of chemical current source according to

the present invention achieves improved technical characteristics, and yields

chemical current sources which are capable of fast discharge.

EXAMPLE

Granules of magnesium and aluminum were mixed with granules of

solder and KOH and nickel, zinc and titanium nitride at the following mass

proportions: 44%, 45%, 3%, 1%, 1%, 4% and 2%, respectively. The

mixture obtained was enclosed in an electrical graphite crucible, and heated

to the fusion point under hydrogen. The resultant substance was cooled

down to an acceptable temperature for fabrication of electrodes.

A chemical current source anode made as described above may be

used to fabricate a chemical current source. The anode is immersed in an

electrolyte, which is preferably water. Also immersed in the electrolyte is

a cathode which can be made from any suitable material, preferably

activated carbon. Preferably, means are provided to heat the anode of the

current source in order to improve its performance.

Precisely the same techniques described above can be used to

fabricate an anode for use in a storage battery. Preferably, the mixtures

used to fabricate an anode for use in a storage battery will, in addition, also

contain 3-5 wt% of nickel hydroxide.

A storage battery anode made as described above may be used to

fabricate a storage battery. The anode is immersed in an electrolyte, which

is preferably an alkaline solution containing one or more of the following:

zincates, stannates, aluminates, fluoric sodium, or potash. Also immersed

in the electrolyte is a cathode which can be made from any suitable

material, preferably an oxygen-nickel cathode.

A chemical current source and a storage battery as described above

may be combined to form an energy plant. One example of such an

energy plant is depicted schematically in the Figure. The energy plant is

made up of a chemical current source 10 and a storage battery 12.

Chemical current source 10 includes a current source anode 14 and a

current source cathode 16 immersed in a current source electrolyte 18.

Heating means 20 are available to heat current source anode 14.

Storage battery 12 includes a battery anode 22 which is electrically

connected to current source anode 14, and a battery cathode 24 which is

electrically connected to current source cathode 16. Battery anode 22 and

battery cathode 24 are immersed in a battery electrolyte 26.

While the invention has been described with respect to several

preferred embodiments, it will be appreciated that many variations,

modifications and other applications of the invention may be made.