CA1293019C - Process for stabilising primary electrochemical generators having reactive zinc anodes, with aluminum or magnesium; stabilised anode made according to saidprocess; and generator including said anode - Google Patents

Abstract

"PROCESS FOR STABILIZING ELECTROCHEMICAL GENERATORS WHICH PRIMERS WITH REACTIVE ANODES IN ZINC, ALUMINUM OR MAGNESIUM; STABILIZED ANODE OBTAINED BY THIS PROCESS; AND GENERATOR COMPRISING SUCH ANODE" The subject of the invention is a method for stabilizing a primary electrochemical generator comprising at least one reactive anode made of a metal taken from the group of zinc, aluminum and magnesium, characterized in that a percentage of 0.001% to 1% by weight, relative to the metal, is added to said electrode '' at least one alkyl sulfide and polyethoxylated alcohol corresponding to the formula RS- (CH2) 2- (O-CH2-CH2-) n-OH. formula in which: - R is an alkyl radical, branched or unbranched, an aryl radical or an alkylaryl radical (R is preferably the tertiododecyl radical), and - n is between 2 and 100. It also relates to an anode obtained by the aforementioned process and a primary electrochemical generator, with alkaline or saline electrolyte, comprising an anode of this type. (no drawing)

Description

~ Z ~ 3 ~ 9 "PROCESS FOR STABILIZATION OF ELECTROCHI11 GENERATORS ~ -PRIMARY MATERIALS WITH REACTIVE ANODES IN ZINC, ALUMINUM OR
MAGNESIUM; STABILIZED ANODE OBTAINED BY THIS PROCESS OF: AND
GENERATOR COMPRISING SUCH ANODE "
The invention relates to electrochemical generators primary mics, or electric batteries, comprising very reactive anodes made of zinc, aluminum or magnesium, in particular of the type of manganese dioxide / zinc, oxide of ar-gent / zinc, mercury oxide / zinc, air / zinc, chloride lO silver / magnesium and air / aluminum, with an electrolyte alkaline or saline, such as an aqueous solution of potash or zinc chloride and ammonium chloride respectively tively, solution in which the anode is corrodable.
If such batteries provide lS high energies, they present, due to the corro-of their reactive anodes in the electrolyte alcalln or saline, fairly reduced stability with - loss of battery capacity during storage resulting from partial solubilization of the anode in the electrolyte, - continuous and significant release of hydrogen gas causing the electrolyte ejection and inflates it sometimes even the bursting of the pile;
the importance of these harmful phenomena is increased in temperature rise, for example in case of storage in a hot country.
To overcome these disadvantages and stabilize a battery of the aforementioned type, in particular with an alkaline electrolyte, we proposed to stabilize it either by incorporating mercury in the anode ~ with the formation of an amalgam) in the case of zinc, that is to add certain organic compounds ques.
We first proposed to incorporate a tain percentage of mercury, for example from 5 to 15 Z in weight compared to the active metal in the case where this one , _.
lZ93 ~ 19 is made up of zinc, especially for a battery with alkaline electrolyte.
In fact, mercury has the property of ac-increase the hydrogen surge of the metal in which it is incorporated (all the more so since its concen-tration is important) in inhibitan ~ the reaction of proton reduction, Unfortunately mercury and more particularly its compounds are toxic. This requires measures strict safety measures in the manufacturing process industrial cation, and, moreover, dissemination batteries discarded after use is a cause of dangerous pollution.
There is therefore an interest in avoiding the use of mercury or at least reduce the mercury content of batteries for ecological reasons. Besides the rule-mentation tends to gradually limit this content.
But a mercury content compared to zinc in 1 lower anode at about 3 ~ /. by weight does not pro-not provide sufficient stability to electro-alkaline lyte, It has also been proposed to add to a zinc, aluminum or magnesium anode, for stabilization ser, a number of organic compounds, such as oleic acid diethanolamide, monolauryl-ether, amines, quaternary ammonium compounds and certain polymers of ethylene oxide, to replace place, in whole or in part, the mercury.
Such compounds unfortunately do not provide sufficient stability and are themselves often of em-difficult bending or reduced efficiency.
As regards more particularly the po-ethylene oxide lymers, mention may be made of the US patent n 3,847,669 and the French patent n 2,156 ~ 662 of the Union Carbide, who propose to add, to a zinc anode containing less than 8 ~ /. of mercury, a po-lZ93 ~ 19 ethylene oxide lymer, taken from the group of di-, tri- and poly-ethylene glycols having a molecular weight medium from 190 to 7000, their alkyl ethers and their of alkanoic acids, this in order to improve the sta-bility of the batteries provided with such anodes. In these two patents, the use of al- radicals is recommended.
coyl or alkanoate has 1 to 4 carbon atoms.
On the other side, the woman described in the patent French no. 2,567,328, made available to the public on January 10 1986 for "Process of stabilization of the genera-primary electrochemical teurs ~ reactive anodes in zinc, aluminum or magnesium and anode for such a generation stabilizer by this process ", a stabilization process of primary electrochemical generators carrying at least one reactive anode made of a metal taken from the group of zinc, aluminum and magnesium, characterized in that one adds to said electrode a percentage from 0.01 Z to 1 Z by weight, relative to the met tal, of at least one perfluoric organic compound of the type ethoxyl fluoroalcohol ~
Contrary to these teachings, the demand-resse has now discovered that it is possible to stabilize a reactive anode made of zinc, aluminum or-ma-gnesium of a primary electrochemical generator, a alkaline or saline electrolyte, incorporating an anode a very small amount (generally less than 1 Z in weight relative to the metal of the anode ~ d at least one s ~ lfure of alkyl and polyethoxylated alcohol of formula RS- ~ CH2) 2- ~ O CH2 CH2 n ~ 1 in which :
- R is an alkyl radical, branched or unbranched fié, an aryl radical or an alkylaryl radical, and - n is between 2 and 100.
The subject of the invention is therefore:
a) a method of stabilizing a generator primary electrochemical comprising at least one anode ~. ,, '.
1293 ~ 9 reactive into a metal taken from the zinc group, aluminum and magnesium, characterized in that we have-add to said anode a percentage of O, OO1 Z. to 1 X, erl weight, relative to metal, of at least one sulfide of alkyl and polyethoxyl alcohol corresponding to the formu-RS- ~ CH2) 2- (o-cH2 CH2) n (1) formula in which:
- R is an alkyl radical, branched or unbranched fié, an aryl radical or an alkylaryl radical, and - n is between 2 and 100:
b) a stabilized anode obtained by this process;
c ~ a primary electrochemical generator (battery electric) comprising such an anode.
Preferably:
- R is an alkyl radical having about 12 atoms carbon, and / or - n is between 2 and approximately 20.
In the preferred embodiments, the radi-cal R is branched and it is notably constituted by a tertiary radical.
A single compound can be used.
in the above formula (1) or a mixture of two or more compounds corresponding to this formula.
Preferably we also add to the anode, '' when it is zinc, mercury, but in a quan-relatively small tite less than 2% by weight per compared to metal, especially when it is intended for an alkaline electrolyte generator.
Thanks to the invention, the corrosion of the metal of the anode and we avoid decreases in capacity of the battery during storage, the release of hydro-gene, electrolyte leakage and swelling of the battery, without resorting to the addition of mercury or ~
at the very least, for a zinc electrode, with an ad-edition of mercury in a reduced content responding to ~
,,, ~ B ~. .
1293 ~ 19 standards and environmental requirements.
The invention could, in any case, be well understood using the additional description which follows, What complement is, of course, given above all to As an indication.
A. Zinc or Dile electrode ~ called "alkaline", has elect alkaline trolvte.
An anodic mixture is prepared, intended to cons replace the negative electrode, or anode, of a battery, successively introducing into a blender the of zinc amalgamated at 1 't., of the potassium solution to 40 ~~, a gelling agent such as carboxymethylcellu-lose, and the inhibitor according to the invention. to know in the proportion of 500 ml of potash solution and 50 9 of carboxymethylcellulose per kg of amalgamated zinc.
The inhibitor can be distributed on the surface of the zinc amalgamated using a non-aqueous solvent (such as ethyl alcohol or acetone) that you evacuate then pore, or by mixing the inhibitor with the solution.
potash.
The anodic mass thus obtained is tested in a 10 N potassium hydroxide solution at 45 ° C. and the. vi-corrosion rate in ~ l / g / day (microliter of hydrogen CTPN per gram of zinc per day). A higher speed less than 10 ~ l / g / day is unacceptable in a genera-electrochemical cell.
We know that the rate of corrosion (determined by the volume of hydrogen released per gram of sample and. per day when this sample is immersed in the electrolyte in question) is largely used for the control of amalgam samples and shows a very good correlation with conservation effective electrochemical generators. To access After the test, we generally operate at 45 ° C.
~ HIS comparison, a zinc powder not amalgam has a very significantly higher corrosion rate ~ z ~
less than 10 ~ l / g / day (of the order of 2000 ~ l / g / day), a zinc powder amalgamated at 0.2 7. at a speed of corrosion of the order of 200 ~ 1/91 day, at 1 Z. a speed-corrosion of around 20 ~ l / g / day, therefore still greater than 10 ~ 4l / g / day, amalgamated at 5%
corroslon of about 1.5 ~ l / g / day, the latter being acceptable in most generators.
Examples 1 to 4 The inhibitor consists of a compound according to formula (1) in which R is the tertiodo- radical decyle, with different values of n:
Example 1: n - 2 ~ Example 2: n = 7 Example 3: n = 11 Example 4: n = 20 The inhibitor content is in each case 0.1 ~ /. by weight compared to zinc.
We made measurements of the speed of erosion and we found in ~ l / g / day:
- for example 1: 1.93 - for example 2: 1.57 - for example 3: 1.24 - for example 4: 1.07 If mercury is also used, this is that is to say if you use amalgamated zinc powder 0.2 Z of mercury and 0.1 Z of inhibitor according to the examples ples 2 to 4, we found an express corrosion rate mée in ~ l / g / day:
- for example 2: 4.6 ~ l / g / day : 30 - for example 3: 2.8 ~ l / g / day - for example 4: 1.9 ~ l / g / day EXAMPLE OF INDUSTRIAL APPLICATION IN A PEEN
alkaline erector with zinc electrode, ~ es primary generators, as described in 35 the French patent n 2.503.935 of the plaintiff, have was assembled in two series:
- one with a compound anode mass zinc powder amalgam to S / an electrolyte consisting of killed by a 40 / potassium solution. and a gel agent Icarboxymethylcellulose), the proportions being 300 ml of potassium hydroxide solution and 25 9 of carboxyme-thylcellulose per kg of amalgamated zinc;
- the other comprising in the same electrolyte and the same agent gelling an anode mass whose zinc powder is only amalgamated to 1 /. but in which during mixing with the electrolyte and the gelling agent, the compound (1) of Examples 1 was introduced to 4 above in the proportion of 0 1 Z by weight per compared to zinc.
Both series have been stored for three months at 45 C. At the end of this storage period the servation showed no electrolyte exudation at the outside of the batteries due to possible overpressure.
Removing the batteries revealed that there is no had no expansion of the anode gel. Finally the elements of these two series in module R 20 unloaded on a resistance of 3 9 ohms in continuous mode, present the same dispersion in the discharge time: 59 h ~ 1 h, that is to say that there is no loss of capacity of the batteries of the second series compared to those of the Z5 premiere.
Another example of industrial application in a generator alkaline with zinc electrode For industrial battery applications where the electrode negative consists of a gel whose zinc metal content is relatively tively low, for example ~ 52% (by mass), compared to the trolyte, and for which the mercury content of the zinc alloy is also low, for example less than 1%, we see that we have interest in maintaining electrical pe ~ ormances, in particular the voltage level, to lower the content of inhibitor dan9 anodic gel of the battery at less than 0.01% compared to zinc, i.e. between 100 ppm and 10 ppm. Thus, for an anodic gel comprising:
- 8 _ ~ 2 9 3 ~ 1 9 52 parts of a zinc alloy with 100 ppm of cadmium and 1% mercury for 48 parts of 8.5 N KOH solution containing 6% ZnO and 6%
carboxy methyl cellulose, 50 ppm compared to the zinc alloy, a dodecyl mercaptopoly alcohol-ethoxylated are added during the preparation of the mixture, preferably right after amalgamation, and intimately mixed.
This low content between 10 and 100 ppm of inhibitor can also apply to other gel compositions, in particular those which are richer in zinc, since we do not want an excess excessive corrosion protection.
~. Dour Dile zinc electrode, so-called electro saline - saline trolvte.
It is well known that dioxide type batteries of manganese / zinc, called "salt cells", use a electrolyte composed of an aqueous chloride solution of zinc and ammonium chloride, in which 1 elec-zinc trode tends to corrode to form hydrogen, which has the effect of causing electrolyte leakage, by puncturing the zinc cup, and loss of capacity in stock ~ age.
The zinc electrode of these batteries consists c ~ e sheet metal, therefore less reactive than powder ~ dlvisee of alkaline generators. This zinc sheet is only amalgamated on the surface, the weight of mercury per pile is consequently 1000 times weaker than that which is necessary for so-called "alkaline" batteries alkaline trolyte.
The inhibitory effect of the compounds according to the invention tion is highlighted by the corrosion test ef-performed at ~ SC in a saline solution comprising 25 Z
by weight of Cl2Zn, 25 Z by weight of NH ~ Cl and the complement in water.
1293 (~ 19 g The use of powdered zinc specimens has the advantage of providing a rapid response and statistically more homogeneous. Indeed, the tabs tai.llées in a pile bucket have a large het: erogeneity, of structure due to the spinning lines of the tube, and consequently a great dispersion in the re-responses to the corrosion test.
The ratio of active areas and therefore corrosion rates between the powder and the sheet is close to 5000.
The following corrosion rates were obtained:
a) control electrode without mercury and without inhi-biteur according to the invention 2000 ~ l / g / day;
b) electrode with 0.01 Z by weight of the compound (1) cited above - example 2 327 ~ l / g / day Example 3 170 ~ l / g / day Example 4 136 ~ l / g / day c) electrode with 5 Z by weight of mercury 175 ~ l / g / day The inhibitory effect of alkyl sulfide and al-cool polyethoxylate of formula (1), according to the invention, is very clear, even in saline environments.
As it goes without saying and as it follows from 25 their already from the above. 1 invention is not limited to those of its modes of application and embodiments.
more specifically envisaged; she in embraces, on the contrary, all variants.

Claims (11)

- 10 -The embodiments of the invention, concerning the-what an exclusive property right or lien is claimed, are defined as follows: 1. Method for stabilizing a generator primary electrochemical comprising at least one anode reactive in a metal chosen from the zinc group, aluminum and magnesium and characterized in that we add at said anode a percentage of 0.001% to 1%, by weight relative to the metal, at least one alkyl sulfide and polyethoxylated alcohol corresponding to the formula:
RS- (CH2) 2- (O-CH2-CH2-) n-OH (1) formula in which:
- R is an alkyl radical, branched or unbranched, a aryl radical or an alkylaryl radical, and - n is between 2 and 100. 2. Stabilization process according to the claim tion 1, characterized in that R is an alkyl radical having 12 carbon atoms. 3. Stabilization process according to the claim tion 1 or 2, characterized in that R is a radical branched. 4. Stabilization process according to the claim tion 1 or 2, characterized in that R is a radical tertiary. 5. Method according to claim 1, characterized in that R is the tertiododecyl radical. 6. Stabilization process according to the claim 1, 2 or 5, characterized in that n is included between 2 and about 20. 7. Stabilization process according to the claim tion 1, 2 or 5, characterized in that the anode is made of zinc and additionally contains mercury in an amount less than 2%
by weight compared to metal, especially when it is intended for an alkaline electrolyte generator. 8. Stabilization process according to the claim tion 1, 2 or 5, characterized in that a mixture of two or more compounds according to formula (1) of claim 1. 9. Reactive anode for electrochemical generator primary, in a metal chosen from the zinc group, aluminum and magnesium and characterized in that adds to said anode a percentage of 0.001% to 1%, in weight, relative to metal, of at least one alkyl sulfide and polyethoxylated alcohol corresponding to the formula: ' RS- (CH2) 2- (O-CH2-CH2-) n-OH (1) formula in which:
- R is an alkyl radical, branched or unbranched, a aryl radical or an alkylaryl radical, and - n is between 2 and 100. 10. Primary electrochemical generator at alkaline electrolyte, characterized in that it comprises a anode according to claim 9, this anode being made of zinc and additionally containing mercury in an amount less than 2% by weight relative to the metal. 11. Primary electrochemical generator at saline electrolyte, characterized in that it comprises a anode according to claim 9.