DE2231472A1 - GELATED ELECTROLYTE FOR ELECTROCHEMICAL ELEMENTS AND ELECTROCHEMICAL ELEMENT WITH SUCH ELECTROLYTE - Google Patents

Description

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SÖCiBTE DES AGGuITOMiETiUES FIlOiIS ET DE TEAS TION: 56 * Avenue de. Metz _t ° 3 ROMÄIHVILLE (France)

ELECTROLYTE FUE: EGGROCHEMISGHE EIEKTE . KDRKSRQGHTiMISEHERS- EEEMENT 'WITH SUCH ELECTROLYTE,

The invention, "relates to gelled electrolytes for electrochemical elements with an · alkaline solution * der a gelling agent is added.

Natural gelling agents for such electrolytes are known. Strong stoffe-- as beispielsweise.- potato .- ^ _is-; Rice and cereal strong or the like used ..

It has been found, however, that: this strength sinks ! Well proven with a high concentration of Älknli ..- With one FaIilati ^ el®sung: * in de ^ das: Gel retains its characteristics and säe!)) smells liquefied, so the formality must be more than HI IfI amount to ..,. If the cone is too small, the bracing will burst rlie Starfeek ^ raer and. no longer bind the electrolyte- ..

Such a high concentration of potassium hydroxide E lek tr ο. Iy ten own !; do not fall into low temperatures * and theirs is.t lower than. of more dilute solutions.

2 § S 8 8 3/0 7 0 2 ORIGINAL INSPECTED

As a result of the electrochemical reactions that take place especially on the negative electrode Water are formed, whereby a dilution of the electrolyte occurs, which in turn causes the starch grains to crack is effected at least in certain places "

This destroys the gel _f which can cause the electrolyte to escape *

The invention eliminates these disadvantages,

The invention relates to a gelled electrolyte For electrochemical elements with an alkaline solution to which a gelling agent has been added, characterized in that that the gelling agent contains crosslinked or modified starch substances.

Such starches, which have been treated with certain reagents in a known manner, for example epichlorohydrin, withstand the action of alkaline solutions significantly better than natural starches, regardless of their concentration. Such starch substances are described, for example, in the American patent specification 2 74 "1P.J"

Potassium hydroxide can therefore be used with modified starches solutions, a normality of less than 11 JN- use b v / ground without the gels liquefying ..

Further features of the invention contain the description of a AusfulirnngsbeisrLeIs on the basis of the drawing,

20988 »/ 07β2 BAD ORIGINAL · /

which show the swelling curves of the various starch substances in aqueous potassium hydroxide solutions illustrated.

Therein the corrnality N - of the potassium hydroxide solution is as The abscissa and the percentage G of swelling of the starch granules are plotted as the ordinate.

The curves (Δ), (B) and (C) show those with corn starch, results achieved with natural potato starch or corn flour starch.

From this it can be seen that when the formality of the potassium hydroxide solution reaches a ^V 7ert of significantly less than 11 H, a very strong swelling of the starch grains is observed, whereby a liquefaction of the gel occurs.

Curves (D), (7,) and (P) show the results obtained with crosslinked starch, which one more or has been exposed to less significant networking.

As is well known, the degree of treatment becomes starch
determined by the following experiment:

^r 5 g of starch are cooked in 100 cm3 20 minutes ^ and Beliandlungsgrad is determined by the volume of within 24 Stundeii located remote strength.

The curve (D) applies to treated potato starch with a rating of / 17. .

The curve (E);.; Ilt for treated potato starch with a degree of exposure of 3 '>.

? 0 Ji V, R 3 / η 1 0? BATHROOM / ORIGINAL

The curve (F) applies to treated potato starch with a treatment degree of 28.

The swelling measurements were carried out as follows;

The starch is scraped open in the Kai il auge I'd solution, in each case 5 g per 100 cm3 for two hours at 20 ° C, then 10 cm3 of the slurry are centrifuged. The swelling of the starch corresponds to the volume it occupies, expressed in 1/10 cm3.

As can be seen from the drawing, the swelling of the crosslinked starch with any normality is the Kai i lauge 3 "ö si ing then practically constant.

A degree of treatment of the strength between 25 and 50 is therefore the most suitable, because there is a risk of one Disintegration of the gel over time if the degree of treatment is more than 50, and if it is less than 25, suffice the gelling properties of the starch used do not affect "

The amount of crosslinked starch per liter of alkaline Solution can be very different, and it depends in particular on the desired degree of fluidity of the gelled Electrolytes.

At a concentration of the crosslinked starch of 150 to 240 g / l, an electrolyte is achieved, its mobility in particular for elements with depolp, risation durcl · Air is suitable.

BAD ORIGINAL, 83 / Π.70? '" ^{% /}

The electrolyte according to the invention is particularly suitable for use in electrochemical elements negative electrode called zinc base.

The discharge reactions in zinc are as follows:

Zn + 2 OH - > Zn (OH) ₂ -: - 2 e (D.

Zn + 4 OH - ^ Zn O ₂ ² "■ + 2 H ₂ O + 2e ~ - (2)

The reaction (D occurs when the zinc hydroxide does not dissolve in the electrolyte, i.e. when it is saturated with zincate, while in the opposite case the Reaction (2) occurs.

Reaction (2) produces hater, which causes the electrolyte to be diluted in places can,

The gelation of the electrolyte by natural means Starch occurs, the water produced can destroy the gel by breaking the starch grains as a result the dilution of the electrolyte occur *

■ ^T 7enn contrast, according to the invention, the electrolyte-linked starch gels is not affected by the formation of water from the gelled state at all.

¹ ^ in accordance with the invention gelled electrolyte can advantageously be used for preparing a negative active material, mixed with Zinlcnulver be used.

As a cross-linked starch, for example, starch from 209883/0702 BAD * 'original

Corn, potatoes, or a mixture of both are used.

The invention also provides the use of a mixture of natural and crosslinked starch, their The proportion must be greater than the amount of natural starch. Good results have been achieved with mixtures in which the modified starch content was reduced to 60 percent.

- Claims 209883/0702

Claims (6)

-τ- PATEET CLAIMS 1. Gelled electrolyte for electrochemical elements with an alkaline solution to which a gelling agent has been added, characterized in that that the gelling agent contains modified or crosslinked starch substances; 2. Electrolyte according to claim 1, characterized gekennz e i without t that the alkaline solution consists of potassium hydroxide solution ". 3. ■ electrolyte according to claim 2, characterized I do not mark that the formality of the potassium hydroxide solution is less than 11 N. 4 «electrolyte according to one of the preceding claims, characterized in that "when using a mixture of 5 g of cross-linked starch and 100 cm3 of water, which is heated for 20 minutes at approximately 100 ° C, after a settling time of 24 hours Deposit 25 to 50 cm3. 5. Electrolyte according to one of the preceding claims characterized in that the gelling agent from a collection of natural and interconnected There is starch, the amount of crosslinked starch being greater than that of the natural starch. 209883/0702 223H72 6. Electrolyte according to claim 5, characterized in that that the proportion of cross-linked starch is more than 60 percent. 7 «Electrochemical element according to one of the preceding Claims, characterized in that that it has an electrolyte. 0. Element according to claim 7 »d a d u r c h characterized in that the negative active mass Zinc base is made. Γ. P'lement according to claim 8, characterized in that the negative active mass is made a mixture of zinc powder and the electrolyte after one of claims 1 to 6 consists. 2ÜS8B3 / 0702