US3000996A - Accumulators - Google Patents

Description

ACCUMULATORS Filed June 27, 1957 Fluidand Gus-Tight Accumulator containing:

Elecfrolye,

Electrodes Absorbing Substances and Redox System Foriners.

INVENTOR HUBERT STEPHAN USEL BY whim ,35% M g;

ATTORN EYS United States Patent 3,500,996 ACCUMULATORS Hubert Stephan Use Sistrans (Tyrol), Austria Filed June 27, 1957, Ser. No. 668,505 Qlaims priority, application Austria July 2, 1956 6 Claims. (Cl. 136-9) This invention relates to a fluid and gas-tight totallyenclosed accumulator.

In accumulators of such kind the formation of gases which may occur by loading, discharge, self-discharge and chiefly by overloading either has to be prevented or the gases must be bound. For example, in overloaded lead accumulators oxygen forms itself at the anode and hydrogen at the cathode.

Object of the invention is to prevent the formation of small gas-bubbles or to bind the occurring gases in the electrolyte, respectively in or at the electrodes.

A special purpose of this invention is to prevent the formation of molecular oxygen and hydrogen in overloaded lead accumulators, or to bind same gasiform oxygen and hydrogen. The bond may be effected by adsorption of the oxygen and hydrogen molecules, or formation of oxygen and hydrogen is prevented by chemical processes.

The invention further has the purpose to provide an accumulator which is able to work in every position whatever.

The solution of this problem proposed by the invention consists in creating a fluid and gas-tight totallyenclosed accumulator containing, besides electrolyte and electrodes, adsorbing substances as well as substances qualified to form a redox-process with the occurring gases.

It is required of these substances that they secure the slight reversibility of the redox-process. Moreover it is required of said substances that throughout the redoxprocess they do not substantially vary the potential differences in the accumulator.

Therefore such substances preferably are used which in initial condition as well as in reduced and oxidized state are insoluble in the electrolyte.

It is suitable to incorporate such substances into one or both electrodes or to add them on the electrodes. sub stances of that kind do but trivially modify the potential difierences and originate no noticeable self-discharge.

If the substances of the redox-system in initial condition are soluble in the electrolyte and at least partially dissociated, then they separate at the electrodes. Through this separation, however, the substances should not be allowed to form any compounds with the electrodes, or they should only form compounds difiicultly soluble in the electrolyte. Besides, the reversibility should, of course, be assured.

Especially suitable for this purpose are polyvalent elements, for example oxides, acids and salts of chromium, titanium, vanadium, manganese, Wolfram, molybdenum, uranium and the like. The properties which compounds out of said elements have in common are a good oxidizing and reducing effect.

Out of more, here are some compounds of said kind particularly suitable for acid accumulators, for example for lead accumulators: H2C1'2O7, CrO HVO V 0 B21103, TiSO H2M0O4; HMGO4; HRGOr}.

These are thoroughly acids or oxides of the elements quoted. They have in common a tendency to forming complex compounds.

The property to form complex compounds deserves particular consideration why it generally implies still more favourable reducing effects. For this reason it may appear suitable not to add the customary compounds to the elements quoted, out of which the complex come together with hydrogen and oxygen.

Patented Sept. 19, 1961 pounds are formed afterwards, but to add primarily prepared concentrates of the complex compounds.

Following complex compounds may be mentioned for example to be applied in case of acid electrolytes: Complex acids with silican or with a metal as central atom for example tetrachromic acid, metawolfram acid.

In case of basic electrolytes it will be more suitable, instead of acids or oxides, to use bases or salts of same elements or of similar ones.

Lead accumulators with sulfuric acid electrolytes form for example some heteropoly acids with the hydrogen separated at the cathode and with the oxygen separated at the anode and create in this way an effective redoxsystem. Periodic and vanadic acids should be mentioned as an example, for heteropoly acids. Further examples are heteropoly acids which are formed from vanadic acidwith silicic acid, from vanadic acid with boric acid and from vanadic acid with telluric acid. Said heteropoly acids are added to the electrolyte.

Besides heteropoly acids, compounds of elements of the iron series are qualified to form a redox-system In consideration of the easy but undesirable separation generally occurring atthe electrodes when such compounds are used it will be preferable to use compounds which. are insoluble or at least-nearly insoluble. Thus are said compounds substantially in suspension in the electrolytes. Examples thereof are basic sulfide of cobalt Co(OH)S and of nickel Ni(OI-I) S.

In a similar way titanium dioxide TiO or titanium (HI) oxide Ti 0 form together with the oxygen and hydrogen separated at the electrodes an eifective redoxsystem. Thereby the titanium dioxide or the titanium (III) oxide may be stored in the cathode for example by mixing it up with the lead powder out of which the cathode is made by pressing method. Another means consists in spreading the titanium dioxide, respectively the titanium (III) oxide upon the surface of the cathode which in this manner is coated with a porous layer of titanium dioxide, respectively of titanium (III) oxide. As a third possibility, the titanium dioxide, respectively titanium (III) oxide may be suspended in the electrolyte. In the latter case a larger quantity of titanium dioxide or titanium (III) oxide will be present than in the other cases where the substances are provided directly at or into the cathode.

In lead accumulators it is also possible to obtain effective redox-systems for realising the bond of gases occurring at the electrodes by incorporating iodine, arsenic, sulfur and chiefly selenium, into the electrodes, preferably into the cathode, or by addition of same at the electrodes. An alternative possibility consists in solving iodic acid, telluric or tellurous acid, arsenic or arsenious acid, lead sulfide and preferably selenic acid or selenious acid in the electrolyte.

As adsorbing substances it will be suitable to use such substances which have a very large surface and these may be suspended in the electrolyte. Most suitable for example is highly dispersed silicic acid which, when in suspension in the electrolyte, efiects that the electrolyte is converted into pasty state.

Although it is true that the bond of the gases is on the one hand already realised by the adsorbing substances and on the other hand by the substances forming a redox-sys-tem together with the gases separated at the electrodes, a practically useful efiFect is only attained through the co-operation of both kinds of substances.

In fact not only the gases themselves are adsorbed by the adsorbing substances, but equally the other substances of the redox-system. Latter thus are brought into a convenient position to react with the gases and, moreover, self-discharge is strongly reduced. Substantially the se1fspouses discharge is conditioned by the difiusibility of the ions contained in the electrolyte. The diflusion, however, is strongly reduced by the adsorption and by the reduction of the ionic mobility as a consequence of the pasty consistency of the electrolyte.

In many cases, for example when the substances composing the redo-x-system are solved in the electrolyte and the accumulator is in overloaded condition, consequently when no selfdischarge is menacing, a slightdifiusion of the substances of the redox-system is desirable in view of good reaction conditions. Experiments have shown that it is possible to obtain a slight diffusion of the electrolyte in overloading state and a worse diffusion in resting state, by supplying the electrolyte in resting state with as great a quantity of adsorbing substances, for example highly dispersed silicic acid, as is necessary to make the electrolyte pass from the liquid state into a pasty consistency. By overloading and provided that the accumulator is gas-tight closed, the electrolyte spontane ously returns to liquid state as expected.

. The invention is explained more in detail by means of following examples:

Example 1 V In the sulfurc acid electrolyte of a lead accumulatorthe concentration of the electrolyte has the value customary in lead accumulatorsg. to g. highly dis-' persed silicic acid having a surface of 300 mi to 350 m? per gram are suspended per 100 g. electrolyte.

in the negative electrode, titanium dioxide TiO is incorporated, namely substantially in that the titanium dioxide has been mixed up with the lead powder of the electrode and this mixture moulded to electrodes by pressing method. For a permanent loading current of 0.06 ampere, about 1.5 g. titanium dioxide TiO are sufiicient.

In the course of the redox-process, by which the bond of oxygen formed at the anode and hydrogen formed at the cathode is realised, titanium (III) oxide is formed out elf-titanium dioxide and is re-converted into titanium dioxide. In view of the bond of the oxygen formed at the anode, this oxygen must be brought to the cathode. This can occur through diffusion, or in that the oxygen at first escapes and forms a gas-cushion above the electrolyte, and is solved in the electrolyte under the pressure of the gas-cushion. In the cathode, the bond is then realised of the oxygen by the titanium (III) oxide Ti O which was formed by reduction by the hydrogen formed at the cathode.

The voltage of this accumulator-cell during the loading process is of maximum 2.9 volts. The terminal voltage by beginning of the consumption of current is 2.2 volts.

Instead of pressing the titanium dioxide together with the lead of the cathode, titanium may be spread upon the surface of the cathode.

Example 2 Example 2 only differs from Example 1 in that the titanium dioxide TiO is not incorporated to the cathode nor spread upon its surface, but is suspended in the electrolyte. By same permanent loading current of 0.0 6 ampere a quantity of titanium dioxide TiO is, however, necessary which amounts to 2 to 3 g.

Example 3 Like in Example 1 silicic acid is added to the elec' trolyte of a lead accumulator. Further, as initial sub stance for the rcdox-process to realise the bond of oxygen and hydrogen, basic nickel sulfide Ni(OH)S is suspended in the electrolyte. By permanent loading current of 0.06 ampere, 0.6 g. to 3 g. basic nickel sulfide are suflicient.

This accumulator-cell has a peak-tension of 2.6 volts during the loading process and a terminal voltage of 2. volts by discharge beginning.

i The efiect remains equivalent if, instead of basic nickel sulfide Ni(OH)S, there is used basic cobalt sulfide About the same quantity is suspended in the electrolyte. Voltage conditions remain the same.

Equivalent effects also are obtained when basic nickel sulfide or basic cobalt sulfide, instead of being added to the electrolyte, are added to or embedded in the electrodes.

Example 4 Here again is a lead accumulator, to the electrolyte of which and in a like way as in Example 1 highly dispersed silicic acid has been added.

Besides this, the electrolyte contains a heteropoly acid formed from vanadic acid and per-iodic acid. The produced heteropoly acid, which is necessary for adding to an accumulator with a permanent loading current of 0.06 ampere, is formed from the reaction of 021 g. to l g. vanadic acid and an equal quantity of per-iodic acid in sulfuric acid of the concentration of an electrolyte of a lead accumulator.

Such an accumulator-cell has a peak-tension of 2.4 volts in course of the loading process and a terminal voltage of 2 volts by discharge beginning.

Whatl claim is:

l. A fluid and gas-tightly enclosed accumulator comprising, in combination, a fluid and gas-tightly closed casing; electrodes of opposite polarity arranged in said casing spaced-from each other; an aqueous electroylte located in said casing in contact with said electrodes,

whereby during operation] of said accumulator hydrogen and oxygen is generated; anadsorbent substance adapted to adsorb said thus generated hydrogen and oxygen, said adsorbent substance being insoluble in said electrolyte and dispersed in said electrolyte in finely subdivided state so as to at least retard accumulation of hydrogen and oxygen gas within said casing; and at least one oxidizable and reducible material selected from the group consisting of Ti O :TiO and of a heteropoly acid formed of substantially equal weights of vanadic and per-iodic acid, being locatedin said casing in contact with said electrolyte and present in a quantity sufiicient to react with substantially all of said hydrogen gas and oxygen gas generated during operation of said accumulator while said gases are at least partly adsorbed by said finely dispersed adsorbent substance, so as to prevent accumulation of hydrogen and oxygen gas within said casing.

2. An accumulator as defined in clairn l, said accumulator being of thelead-acid type and wherein said dispersed adsorbent substance consists of silicic acid.

3. An accumulator as defined in claim l wherein said oxidizable and reducible material is insoluble in said electrolyte forming a suspension therein.

4. An accumulator as defined in claim 2 wherein said oxidizable and reducible material is composed of TigOgiTiOg- 5. An accumulator as defined in claim 2 wherein said oxidizable and reducible material is composed of a heteropoly acid formed of equal weights of vanadic and per-iodic acid.

6. An accumulator as defined in claim 2, wherein said oxidizable and reducible material is selected'from the group consisting of Ti O zTiog being present in a quantity corresponding to between about 1.5 grams and 3 grams titanium dioxide at a permanent loading current of 0.06 ampere, and a heteropoly acid being present in a quantity equal to that formed from the reaction of between about 0.1 gram to 1 gram vanadic acid with a substantially equal quantity of per-iodic acid at a permanent loading current of 0.06 ampere; and wherein said silicic acid possesses a surface area of the magnitude of between about 300 and 350" square meters per gram, said silicic acid being present in a quantity equal to between about 10 and 15% of the weight of said aqueous electrolyte.

References Cited in the file of this patent 6 Lange et a1 Sept. 27, 1938 Fox Mar. 10, 1953 Jeannin July 21, 1953 FOREIGN PATENTS Great Britain Mar. 13, 1957 Great Britain July 21, 1921 Great Britain June 8, 1938

Claims (1)

1. A FLUID AND GAS-TIGHTLY ENCLOSED ACCUMULATOR COMPRISING, IN COMBINATION, A FLUID AND GAS-TIGHTLY CLOSED CASING: ELECTRODES OF OPPOSITE POLARITY ARRANGED IN SAID CASING SPACED FROM EACH OTHER; AN AQUEOUS ELECTROLYTE LOCATED IN SAID CASING IN CONTACT WITH SAID ELECTRODES, WHEREBY DURING OPERATION OF SAID ACCUMULATOR HYDROGEN AND OXYGEN IS GENERATED; AN ADSORBENT SUBSTANCE ADAPTED TO ADSORB SAID THUS GENERATED HYDROGEN AND OXYGEN, SAID ADSORBENT SUBSTANCE BEING INSOLUBLE IN SAID ELECTROLYTE AND DISPERSED IN SAID ELECTROLYTE IN FINELY SUBDIVIDED STATE SO AS TO AT LEAST RETARD ACCUMULATION OF HYDROGEN AND OXYGEN GAS WITHIN SAID CASING; AND AT LEAST ONE OXIDIZABLE AND REDUCIBLE MATERIAL SELECTED FROM THE GROUP CONSISTING OF TI2O3:TIO2 AND OF A HETEROPOLY ACID FORMED OF SUBSTANTIALLY EQUAL WEIGHTS OF VANADIC AND PER-IODIC ACID, BEING LOCATED IN SAID CASING IN CONTACT WITH SAID ELECTROLYTE AND PRESENT IN A QUANTITY SUFFICIENT TO REACT WITH SUBSTANTIALLY ALL OF SAID HYDROGEN GAS AND OXYGEN GAS GENERATED DURING OPERATION OF SAID ACCUMULATOR WHILE SAID GASES ARE AT LEAST PARTLY ADSORBED BY SAID FINELY DISPERSED ADSORBENT SUBSTANCE, SO AS TO PREVENT ACCUMULATION OF HYDROGEN AND OXYGEN GAS WITHIN SAID CASING.

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