CH650362A5 - BIVALENT SILVER OXIDE CELL AND MANUFACTURING METHOD THEREOF. - Google Patents

Description

The present invention relates to a bivalent silver oxide battery. It relates more particularly to a bivalent silver oxide cell having remarkable improvements concerning the electrical characteristic, the storage characteristic, and the characteristic of leakage resistance, by the fact of improvements in its stability in the solution. alkaline and the positive electrode manufacturing method. The invention also relates to a method of manufacturing this cell.

A conventional bivalent silver oxide cell or (cell cell), without the addition of a stabilizer, lacks stability since the gas evolution volume O 2 caused by dissolution in the aqueous alkaline solution is large. Thus, the bivalent silver oxide battery cell is disadvantageous in that it dissolves itself in the aqueous alkaline solution, which reduces the electrical capacity of the bivalent silver oxide. In addition, the gas 02, generated by the dissolution of the bivalent silver oxide oxidizes the separator, which deteriorates it or causes a self-discharge of the battery cell. The O 2 gas which diffuses to the positive electrode enters the negative electrode via the separator, which oxidizes the zinc and deteriorates the electrical capacity of the latter. The acceleration of the oxidation of zinc results in the surface of the zinc being coated with a passive coating layer, such as zinc oxide, and this stops the discharge of the battery despite the fact that it still remains active zinc as the active material of the cell.

Thus, the battery cells conventionally using unstable silver oxide at the positive electrode, without the addition of a stabilizer, prove to be of inferior quality as regards the storage characteristic.

In the conventional silver cell using bivalent silver oxide, which is unstable and dissolves easily in the aqueous alkaline solution, there is an acceleration of the losses or leaks of alkaline electrolyte towards the outside, since the internal pressure of the battery cell is higher, due to the fact that O2 gas gradually accumulates inside.

To overcome the aforementioned drawbacks, a method of coating the surface of the AgO powder with lead acid silver (plumbic acid silver) is described in US Patent Specification No. 3,017,448. AgO powder coated with lead acid silver (plumbic acid silver) is difficult to reduce, the silver layer is difficult to form on the surface of the pellet of the positive electrode, and therefore the battery impedance becomes higher.

The gas evolution volume 02 in the case where Zn, Cd, Hg, Al, In, TI, Sn, Pb or W is added to the AgO powder by 1000 ppm was studied by Aldar Tvarusko in J. Electrochem. Soc., 116.1071 (1969). However, the effect of Cd, Al, Pb, V and Cr which is presented in the aforementioned article to improve the stability of AgO turns out to be insufficient.

In general, the object of the present invention is to provide a bivalent silver oxide cell (or cell) having excellent qualities with regard to the electrical characteristic, the electric discharge characteristic, the characteristic electric after storage, the conservation characteristic and the resistance characteristic with regard to leaks, the achievement of this aim being sought in the use of a mixture of positive electrode made mainly of bivalent silver oxide and including Cd and Te, or optionally Cd, Te and one or more components selected from Hg, Tl, Ge, Y, Sn, W, La, rare earth elements, Zn, Se, and Al.

According to the invention, this object is achieved by the presence of the characters set out in the appended independent claim. The dependent claims define particularly advantageous embodiments from the point of view of one or the other or more of the characteristics mentioned above, as well as from the point of view of low cost, reliability, ease Manufacturing.

The accompanying drawing illustrates, by way of example, an embodiment of the subject of the invention; in this drawing:

fig. 1 is a schematic sectional view showing an experimental device for measuring the gas release volume 02,

fig. 2 is a diagram showing the gas evolution volume 02 with different AgO additives,

fig. 3 schematically shows the relationship between the volume of gas evolution 02 and the proportion of Cd and Te,

fig. 4 is a diagram showing the relationship between the content of AgO that remains and the number of days of storage, on the one hand for AgO according to the proposed new design and, on the other hand for conventional AgO, in 40 % KOH at 60 ° C,

fig. 5 shows in section an embodiment of the cell according to the particular design proposed,

fig. 6 is a diagram representing the relationship between the degradation of capacity and the storage at 60 ° C. and at ambient temperature,

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fig. 7 is a diagram representing the relationship between the voltage stability and the storage at ambient temperature,

fig. 8 is a diagram showing the relationship between the quantity of additive and the size of the gas release volume 02 (02 gassing volume),

fig. 9 is a diagram for measuring the cell voltage at -10 ° C. FIG. 10 is a diagram representing the relationship between the number of days of storage and the internal resistance.

The stability of the newly proposed AgO powder, used for the battery cell according to the design proposed by the present invention, as well as the stability of a conventional AgO powder, in aqueous alkaline solution, were compared by measurement, for each , of the gas release volume 02 (02 gassing volume), using the experimental device shown in fig. 1. The gas evolution volume is examined when the amount of a stabilizer added to the AgO powder is changed.

In fig. 1, we see in 1 a graduated glass tube, in 2, an aqueous solution of potassium hydroxide at 40%, in 3, 1 g of bivalent silver oxide powder, in 4 a thermostatic enclosure, and in 5 an aqueous solution at 40 ° C or 60 ° C.

(Example 1)

Fig. 2 shows the gas evolution volume 02 with different AgO additives. The additives which have been added to the AgO are metallic elements of the form CdO, Te02, T1203, respectively by 0.3%, 0.1% and 0.1%.

It is clearly shown in fig. 2 that the gas evolution volume 02 is extremely reduced with Cd0 + Te02 and with Cd0 + Te02 + Tl203 in comparison with AgO without additive.

Table 1 below shows that the AgO is further stabilized with various additives in addition to Cd0 + Te02.

Table 1

Additives vol. clearing. gas

(l / g200 hours)

classic

AgO

-

523

AgO

Cd + Te02

46

according to news

CdO + Te02 + PbO

14

design

Cd0 + Te02 + Tl203

6

CdO + Te02 - {- Ge02

11

CdO + TeOz + HgO

8

In this table, the CdO is added to the agO as the Cd element by 0.3%, the Te02, the PbO, the T1203, the Ge02, and the HgO are added to the AgO, as the Te , Pb, Tl, Geet Hg, by 0.1%.

Thus, it should be admitted that the bivalent silver oxide containing additives is stabilized in the aqueous alkaline solution since the specific ions (ion species) of the metallic elements or metallic compounds contained are introduced into the structural configuration d bivalent silver oxide to consolidate the structure of the crystals although the exact stabilization mechanism remains little explained.

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(Example 2)

Fig. 3 shows the relationship between the gas evolution volume 02 and the amount of Cd and Te added to the AgO. The numbers shown in the figure represent the gas evolution volume of 1 g of AgO in a 40% aqueous KOH solution, at 40 ° C, after 240 hours. Cd and Te are added to AgO as CdO and Te02 compounds.

The figure shows that the gas evolution volume 02 is smaller when the amount of Cd increases. On the other hand, the gas evolution volume 02 turns out to be small when the amount of Te is in the range of 0.05 to 0.3%.

Since the electrical capacity of the positive electrode mixture mainly comprising AgO decreases during the addition of the above-mentioned additives, the proportions Cd: Te02 = 0.3%: 0.1% (CdO: Te02 = 0.34% : 0.13%) are selected to ensure the electrical capacity while minimizing the gas release volume 02.

Hereinafter, the particular design proposed by the invention will be illustrated for the case of AgO with additives, in which Cd: Te: Tl are in the ratio of 0.3: 0.1: 0.1%.

(Example 3)

Table 2

AgO AgO

Volume

Ag2C03

dimen density

density

con clear

cona appa appa-

held gaz02

held (%)

medium rent tent

(%)

(1/200 hr)

parties

(g / cc)

dice

in 40 KOH

cules (ji)

riva

40 ° C

tion (g / cc)

New 98.3 16 0.41 2.96 0.79 1.95

Table 2 shows the chemical and physical properties with AgO to which are added Cd02, Te02, and tl203 in a proportion such as Cd: Te: Tl =

0.3: 0.1: 0.1%. It can be seen that the bivalent silver oxide battery cell according to the proposed design, comprises a high content of AgO and has a small volume of gas evolution 02. Since the average diameter of the powder grains, the apparent density and the apparent tapping density are large, the fluidity of the AgO powder is excellent and the molding characteristics of the granulated tablet are improved.

(Example 4)

Fig. 4 represents the relationships between the content of AgO and time on the one hand for the AgO proposed by the particular design, to which CdO, Te02, T1203 are added in a ratio such as Cd: Te: Tl = 0 , 3: 0.1: 0.1%, and on the other hand for conventional AgO to which no additive is added. A generally accepted method, that is to say the potassium iodide reduction filtration method, is applied for the quantitative analysis of the content of AgO.

The copy of AgO is soaked in a 40% KOH solution at 60 ° C. and the quantitative analysis of the content of AgO is carried out every twenty days.

The figure shows that the difference in AgO content between the AgO powder proposed by the new design and the conventional AgO powder becomes large after 40 days. Furthermore, the AgO content of the conventional AgO powder is reduced to 30% after 60 days and to 10% after 80 days. By

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on the other hand, the AgO content of the AgO powder according to the new proposed design is still maintained at 50% after 200 days. It therefore soon appears that the AgO content of the new AgO powder proposed is much more stable for long-term storage.

(Example 5)

An AgO cell cell according to the proposed new design, using the new AgO powder as illustrated in Examples 3 and 4 is effectively manufactured.

Fig. 5 shows a sectional view through this AgO stack cell which constitutes an embodiment of the proposed new design. In this FIG. 5, we see at 11 a container of positive electrode in which the mixture of positive electrode 12 coated with a thin layer of silver 13, a separator 14 and an absorbent layer of electrolyte 15, are incorporated. The electrolyte is an aqueous alkaline solution mainly consisting of NaOH (sodium hydroxide).

The positive electrode mixture 12, consisting of 95 to 99% by weight of AgO powder and 1 to 5% by weight of polyethylene tetrafluoride (polytetrafluoride ethylene), is pressure molded.

Stable materials, with the lubrication and organic bonding characteristics necessary for die casting, and with good alkali and acid resistance characteristics, are suitable materials as organic bonding agents, alongside powders polytetrafluoride ethylene. For example, olefinic resin powders such as polyethylene and polystyrene, polyamide resin powders, such as nylon, water-soluble polymer powders, such as carboxymethyl cellulose, polyvinyl alcohol and polyacylic acid sodium hydroxide (polyacylic acid soda), are suitable as organic binding agents.

The organic binding agent can be in liquid form such as a dispersion solution or water, but not in the form of powder.

The internal limit value of the amount of additives of the organic binder agent is 1% in consideration of the binding effect. Despite the fact that the upper limit value is not specially restricted, amounts of additives exceeding 5% cause a reduction in the capacity of the battery cell due to the reduction in the amount of AgO powder in the mixture positive electrodes. In addition, if more than 5% bonding agent is added to the positive electrode mixture, the electrical resistance inside this positive electrode mixture increases and the internal resistance of the battery cell increases since the bonding agent is an electrically insulating material. Accordingly, the amount of the binding agent additive is preferably 1 to 5%. The stability of the AgO used for the cell cell according to the proposed new design is not deteriorated even if the amount of binder agent additive exceeds 5%.

In fig. 5, we see at 13 a silver layer formed on the surface of the positive electrode mixture 12. This silver layer 13 is formed by reduction of the surface of the positive electrode mixture by suitable reducing means.

In fig. 5, we still see in 17 the negative electrode container in which is a negative electrode mixture 16 consisting of a mixture of amalgamated zinc powder and one or two of the substances that are carboxymethyl cellulose and polyacrylic sodium acid. The negative electrode mixture is used as it is or in the form of a gel with alkaline electrolyte.

The negative electrode mixture can be molded by light pressures.

Fig. 6 shows the speed of self-discharge of a TR726SW cell cell (outside diameter: 7.8 mm, height: 2.6 mm Zn / NaOH / AgO). To find out the capacity, a battery cell is removed from the thermostatic enclosure at 60 ° C. after 20 days or after 40 days of storage, and it is discharged on a charge constituted by a resistance of 1.5 kiloohms, which lets you know the remaining capacity.

The degree of self-discharge of the battery cell can be calculated after 20 days or after 40 days of storage at 60 ° C. degree of self-discharge =

(initial capacity) - (remaining capacity after storage at 60 ° C) / initial capacity x 100%.

The data represents the mean value when n = 24.

Then, the degree of self-discharge of the battery cell according to the proposed new design, after 14 months of storage at room temperature is compared with a cell of conventional type. The degree of self-discharge after 40 days of storage at 60 ° C of the new battery cell according to the particular design proposed is reduced in the ratio of 1 / 3.2 compared to a conventional battery cell. The degree of self-discharge of the cell according to the proposed new design, after 14 months of storage at room temperature is reduced to an extent of 1 / 1.5 to 1 / 2.8 compared to a cell of the conventional type.

Next, the characteristic of the low temperature battery cell is shown in fig. 7. The voltage in closed circuit at -10 ° C is the voltage which occurs when the battery cell is discharged during 7.8 ms on a load Rl = 2 KQ. The cell according to the proposed new design is represented in the figure by the points X, for n = 10, and the conventional stack cell is represented by the points X, also for 10 lots.

Fig. 7 shows that the low-circuit closed-circuit voltage of the cell according to the new proposed design is low in the initial state, but that on the other hand, its modification with the passage of time is much lower.

The changes in the closed circuit voltage at low temperature as a function of the passage of time are smaller for the new battery cell according to the proposed design than for a conventional battery cell because the AgO powder according to the new proposed design is stable in alkaline solution and that the silver layer formed on the surface of the positive electrode is only very slightly oxidized by the gas 02 due to the decomposition of AgO, as is the zinc used for the the negative electrode is also only very slightly oxidized.

As illustrated in Examples 1 to 5, the proposed design provides a bivalent silver oxide battery cell having excellent storage capacity, a closed circuit voltage at low temperature which varies very little with the flow time, and extremely high reliability.

However, when the AgO silver oxide powder cell, according to the proposed new design (Zn / KOH / AgO) is used to provide a large current, for example in a watch with digital liquid crystal display comprising a lamp, the low temperature closed circuit voltage of this battery cell just after its manufacture is approximately 70 to 100 mV lower than that of a conventional type AgO cell.

The above problem can be explained by the following measures:

(1) Optimization of the quantity of additives such as CdO, Te02 and T1203.

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(2) Elimination of Ag in a layer of Ag20 interposed between the AgO and the silver layer formed on the surface of the positive electrode.

(3) Equalization of the thickness of the reduced silver layer on the surface of the positive electrode using AgO s according to the new design proposed with that of the positive electrode using conventional AgO.

The above explanations are verified by the following example:

(Example 6)

First of all, the quantities of additives such as CdO, Te02, and T1203 are optimized.

Fig. 8 shows the relationship between the amount of stabilizer additive and the gas evolution volume 02. In this figure, curve A represents the case where CdO + 'Te02 is used as stabilizer and curve B represents the case where one uses as stabilizer CdO + Te02 + T1203. The point at which the amount of additive is zero corresponds to the volume of gas evolution 02 with a conventional AgO powder. Fig. 8 shows that the gas evolution volume 02 is lower in B than in A. This is due to the fact that thallium oxide is added alongside the cadmium oxide and tellurium dioxide.

The gas evolution volume 02 is lower when the amount of additive is between 5000 and 10 000 ppm.

The components contained strongly affect the stability of the AgO powder in the aqueous alkaline solution either in the form of metallic elements or in the form of metallic compounds.

Subsequently, a battery cell according to the proposed new design, using AgO powder, in which the amounts of stabilizer additives were changed, was manufactured in a similar manner to Example 5. The cell battery in this example is TR926W (outside diameter 9.5 mm, height 2.6 mm, Zn / KOH / AgO, nominal capacity 52mAh).

The characteristic at low temperature, the degree of self-discharge and the degree of appearance of loss of this cell according to the new proposed design, after three months of storage at room temperature, are shown in tables 3 and 4 below. .

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Table 3

quantity of additives (PPM)

characteristic at low temperature self-discharge appearance of leaks

CdO

Te02

Total

(V)

missed (%)

missed (%)

classic cell

0

0

0

1.27 V

15%

30%

new cell. AT

7

3

10

1.27 V

12%

15%

new cell. B

65

15

50

1.27 V

11%

15%

new cell. VS

70

30

100

1.27 V

10%

13%

new cell. D

350

150

500

1.27 V

10%

13%

new cell. E

700

300

1000

1.25 V

10%

13%

new cell. F

3,500

1,500

5,000

1.20 V

10%

12%

new cell. G

7,000

3,000

10,000

1.10 V

10%

12%

Table 4

amount of characteristic self-matching additives

(PPM) at low temperature discharge of

CdO

Te02

ti2o3

Total erasure

(V)

(%)

leaks (%)

classic cell

0

0

0

0

1.27 V

15%

30%

new cell. AT

6

2

2

10

1.27 V

10%

15%

new cell. B

30

10

10

50

1.27 V

10%

15%

new cell. VS

60

20

20

100

1.27 V

10%

14%

new cell. D

300

100

100

500

1.27 V

9%

12%

new cell. E

600

200

200

1000

1.23 V

8%

10%

new cell. F

3,000

1,000

1000

5,000

1.17V

7%

10%

new cell. G

6,000

2,000

2,000

10,000

1.05 V

8%

10%

With regard to the characteristic at low temperature, it is noted that the cells of battery according to the new proposed design are stored in a thermostatic enclosure at -10 ° C, while the measurement is carried out using the diagram shown in fig. 9. The switch S is closed and the minimum closed circuit voltage value 65 for 5 sec is read using the voltmeter V. The data represents an average value when N = 10.

Concerning the method of testing the storage characteristics (measures of the degree of self-discharge) we note

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that the cell cells according to the proposed new design are stored at 60 ° C in a thermostatic enclosure from which they are removed after 40 days, to be discharged on a load resistance of 7.5 KQ, which allows to know the remaining capacity . The degree of self-discharge is calculated by the following formula:

degree of self-discharge =

(initial capacity) - (capacity after storage).

We also have, in percent:

degree of self-discharge =

[{(initial capacity) - (remaining capacity after storage at 60 ° C)} / initial capacity] x 100%

In this formula, the initial capacity of the stack cell is the capacity before storage. The data indicate the mean value for n = 24.

Regarding the leakage test method, we note that the battery cells according to the proposed new design are stored at ambient temperature and humidity at relative humidity of 90 to 95%, these cells then being removed after 1000 hours, and the existence of losses being observed under the microscope. Battery cells with losses on the outside surfaces of the negative electrode are considered defective. The leak appearance data represent the degree of occurrence of leak for n = 100.

Table 3 shows the low temperature characteristic, the degree of self-discharge and the degree of occurrence of battery cell leaks with varying amounts of additives-stabilizers consisting of cadmium oxide and tellurium dioxide. The composition of the stabilizer is approximately in the ratio of CdO: Te02 = 3: 1.

In the table, the conventional stack cell is a cell using AgO powders containing no stabilizer while the stack cells according to the proposed new design, AG, are cells using AgO powders comprising amounts of additives-stabilizers which vary in the range from 10 to 10,000 ppm.

It is clear from Table 3 that the cells of cells A to G, according to the proposed new design, are much better than conventional cells in terms of the degree of self-discharge and the degree of occurrence of leaks (losses of electrolyte to the outside).

The degree of self-discharge and the degree of occurrence of leakage from cell cells using AgO powder without the addition of stabilizer are poorer since the AgO powder without stabilizer gradually dissolves when it is in contact with the aqueous alkaline solution.

The dissolution of the AgO powder causes the following phenomena:

(1) Reduction of the electrical capacity of the AgO powder.

(2) Deterioration of the separator and dissipation of the zinc by the dissolution of the Oz gas released by the AgO powder.

(3) Increase of the internal pressure in the cell of cell by the accumulation of dissolution of the gas Oz resulting from the release of this gas of the powder of AgO.

On the other hand, the cell cells according to the new proposed design prove to be excellent because of the effect of the stabilizer contained in the AgO.

The stabilizer greatly affects the stability of AgO in the aqueous alkaline solution of AgO powder in any form of oxide, hydroxide, metal powder, sulfur and all kinds of salts.

It was found that the low temperature characteristic was closely related to the amount of additive stabilizer. In fact, the low temperature characteristic becomes weaker as the amount of stabilizer additives increases. It is admitted that the reason is that the discharge reaction of the AgO powder is difficult when the discharge takes place with a large current of RL = 200, since the stabilizer stabilizes the AgO powder.

Since the low temperature characteristic for a digital liquid crystal display watch fitted with a lamp requires more than 1.05 V, it seems reasonable to consider the value of the low temperature characteristic of cell F (according to the new design proposed) as a lower limit, taking into account dispersion, etc. In fact, the degree of self-discharge and the degree of occurrence of leakage of the cell cells according to the proposed new design may be higher than those of conventional cells, but keeping the characteristic at low temperature at a suitable value, when the range of stabilizer additive amounts is within the range of 10 to 5000 ppm.

Table 4 represents the characteristic at low temperature, the degree of self-discharge and the degree of occurrence of leaks of cell cells having variable amounts of additive stabilizers, consisting of cadmium oxide, tellurium dioxide, and thallium oxide. For the rest, table 4 is similar to table 3. The composition of the stabilizer is approximately in the ratio of CdO: Te02: T1203 = 3: 1: 1.

As seen in fig. 8, the AgO powder which contains the stabilizer consisting of CdO, Te02 and T1203 is more stable than the AgO powder which contains the stabilizer consisting of CdO and T1203, since the gas evolution volume 02 in the aqueous alkaline solution is small. Thus, cell cells A 'to G', according to the proposed new design, were found to be even better than cells A to G, according to the proposed new design, in terms of the degree of self-discharge and the degree occurrence of leaks.

On the other hand, with regard to the characteristic at low temperature, the cells A 'to G' according to the new proposed design are slightly less good because the characteristic at low temperature decreases with the increase in the quantity of additives of stabilizers, d similar to what table 2 shows.

The characteristic at low temperature of cells E 'to G' is always lower than that of cells E to G. We admit that the reason is that the powders of AgO used for the cells, according to the new proposed design, E ' at G 'are more stable than the AgO powders used for the cells, according to the new proposed design, E at G, and that the IR polarization is greater compared to the discharge reaction at RL = 200 Ohms, as that reaction.

As has been shown, the proposed new design provides a bivalent silver oxide battery cell which is excellent with respect to the low temperature characteristic, the storage characteristic and the resistance characteristic against leaks, by the use, for the positive electrode, of a mixture of positive electrode mainly comprising AgO powder containing a stabilizer at a rate of 10 to 5000 ppm.

To achieve a cell cell voltage of 1.55 V, the bivalent silver oxide battery cell using conventional AgO powder forms a silver layer on the surface of the oxide. bivalent silver used for the positive electrode, by using a reduction treatment and the high electrical potential of 1.85 V (difference in electrical potential between AgO and zinc) is eliminated. The silver layer, however, turns into silver oxide by the fact that it is gradually oxidized with the passage of time, and as a result, the high electrical potential (1.85 V) appears. We admit that the above-mentioned drawback

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is caused by the formation of partial metallic silver in the monovalent silver oxide layer formed between the bivalent silver oxide cathode and the silver layer, when the latter is formed on the surface of the cathode bivalent silver oxide. Thus, the electronic isolation between the bivalent silver oxide cathode and the silver layer is broken. Since the silver layer on the surface is reoxidized, the internal resistance becomes higher due to the following reaction:

AgO + Ag -> Ag20

The particular design proposed tends to eliminate the aforementioned drawbacks; this will be further illustrated in conjunction with the following examples.

(Example 7)

0.1% by weight of CdO powder and 0.03% by weight of Te02 were added to 95% by weight of bivalent silver oxide (AgO), and, moreover, 5% by weight of powder of polyethylene tetrafluoride were added and mixed for one hour. The mixture is transformed into particles, sieved and molded under a pressure of 8 t / cm3 to form agglomerates. The latter are soaked in a solution comprising 90% by weight of methanol and 10% of KOH, for 30 min, then they are washed. Then, these agglomerates are soaked in a solution comprising 20% by weight of KOH, at 60 ° C, for 15 minutes. Then, these agglomerates,

after having been soaked for three minutes in a solution of 50% by weight of ethanol comprising 0.5% of hydrazine, are extracted from this solution, dried at ambient temperature, then stored in a desiccator. Other agglomerates having other amounts of additives are also produced in a similar manner.

(Example 8)

0.01% by weight of powder, CdO, 0.003% by weight of TeOz powder and 0.003% by weight of T1203 powder are added to 95% by weight of bivalent silver oxide powder (AgO), 5% by weight of polyethylene tetrafluoride powder being further added. The whole is mixed for one hour. The mixture is changed into particles, then it is sieved and molded under a pressure of 8 t / cm3 to form agglomerates. These agglomerates are soaked in a solution of 50% by weight of methanol comprising 0.1% by weight of tartaric acid and 5% by weight of KOH solution, this for one hour, then these agglomerates are washed.

Then, they are soaked, for 15 min, in a solution of 10% by weight of KOH comprising 2% by weight of potassium persulfuric acid (potassium persulfuric acid). Then they are thoroughly washed. Then the agglomerates of granules are soaked in a solution of 10% by weight of KOH comprising 1% by weight of tartaric acid, for 20 min. After the reduction, the agglomerates are dried at 40-50 ° C and then stored in a desiccator. Agglomerates comprising other quantities of additives have also been produced in a similar manner.

(Example 9)

0.1% by weight of Cd (OH) powder 2.0.03% by weight of Te (OH) 6 powder and 0.03% by weight of TIOH powder were added to 96% by weight of powder of AgO, 4% by weight of polyethylene powder being additionally added and the whole was mixed for one hour. The mixture was changed into particles, sieved, then molded under a pressure of 8 t / cm2 to make agglomerates. These agglomerates were soaked in a methanol solution comprising 1% KOH, for 30 min, then they were washed. Then,

the agglomerates were soaked for 15 min in a solution comprising 20% by weight of KOH, at 60 ° C., then they were washed. Then, the agglomerates, after having been soaked for 3 min in a 50% by weight ethanol solution comprising 0.5% by weight of hydrazine, were extracted from this solution, dried, at ambient temperature, and stored in a desiccator . Agglomerates having other amounts of additives have also been produced in a similar manner.

The bivalent silver oxide battery cell shown in fig. 5 is made by making use of a positive electrode mixture made as indicated above. This battery cell is of the TR926W type, similar to Example 6.

The low temperature characteristic, the degree of self-discharge and the degree of occurrence or appearance of leaks of these cells according to the proposed new design, were examined after having been stored for three months at room temperature.

Table 5 below shows the results. It is clear from this table 5 that the battery cells according to the proposed new design © to © are extremely good compared to a conventional battery cell, as regards the degree of self-discharge and the degree of occurrence of leaks. . It can be seen from Table 5 that the amount of additives to maintain the low temperature characteristic at an adequate value and to reduce the degree of self-discharge is in the range of 10 to 5000 ppm.

Fig. 10 shows the variations in internal resistance of a conventional cell and a cell according to the proposed new design, after storage at 60 ° C. This figure shows, by the curve "a" that the internal resistance of a conventional battery cell becomes large after 40 days of storage and the curve "b" of this figure shows that the internal resistance of a cell according to the new design proposed increases only very slightly after 80 days of storage.

This is due to the fact that the silver layer 13 is completely isolated from the bivalent silver oxide cathode 12.

The complete isolation of the AgO cathode from the silver layer is obtained as follows: The surface of the AgO cathode has been treated by three treatment processes such as 1. reduction treatment, 2. oxidation treatment, 3. reduction treatment. First, the surface of the AgO cathode was reduced to AgzO by a reduction treatment using a weak reducing agent. At this time, the surface of the AgO cathode will be partially reduced from AgO to Ag. In fact, this layer of Ag20 is electrically conductive since it is composed of Ag and AgO.

Then, the layer of Ag20 on the AgO cathode was oxidized using an oxidizing agent and the metal Ag located with the Ag20 in the layer of Ag20 transforms into Ag20. In fact, the layer of Ag20 becomes truly 100% Ag20 and therefore becomes a perfect insulating layer.

Finally, the layer of Ag20 treated by the oxidation treatment was reduced to a layer of Ag using a strong reducing agent.

In conclusion, the Ag layer of the AgO cathode does not undergo oxidation by the reaction of AgO + Ag-> Ag20, since there is complete isolation between the AgO cathode and the Ag layer.

As illustrated, the particular design proposed provides a bivalent silver oxide battery cell which has a low temperature characteristic good enough to prevent the increase in internal resistance, and which is excellent in its characteristics storage and resistance to leakage, this being obtained by an oxidation treatment of the bivalent silver oxide cathode including additives from 10 to

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Table 5

Weight of additives in%

of the total weight of AgO mixture

characteristic at low temperature self-discharge appearance of leaks

(V)

(%)

(%)

classic cell

-

-

-

1.27

15

30

Example

©

CdO 0.01

Te02 0.003

-

1.27

10

15

new 7

©

0.10

0.03

-

1.27

8

13

©

0.39

0.13

-

1.04

7

12

Example

©

CdO 0.01

Te02 0.003

ti2o3

0.003

1.27

8

12

cell. 8

©

0.10

0.03

0.03

1.27

7

10

©

0.30

0.10

0.10

1.02

4

8

Example

©

Cd (OH) 2 0.01

Te (OH) 6 0.003

TIOH 0.003

1.26

8

15

9

©

0.1

0.03

0.03

1.26

7

11

©

0.3

0.1

0.1

1.02

5

8

5000 ppm after weak reduction treatment to completely establish the insulation between the bivalent silver oxide cathode and the silver layer.

Finally, a method has been illustrated for improving the voltage of the closed-circuit battery cell at low temperature, when a reduction treatment is applied to the surface of the positive electrode using AgO according to the proposed new design and on that of the positive electrode using AgO in a conventional manner, with an identical reduction importance. This is achieved by keeping equal the thickness of the reduced silver layer on the surface of the positive electrode using AgO according to the new 40

proposed design and the thickness of this layer on the positive electrode using AgO in a conventional manner.

(Example 10)

Positive electrode agglomerates of type TR616SW 45 (external diameter 6.8 mm, height 1.6 mm) were produced using AgO on the one hand according to the proposed new design and on the other hand Classic AgO. A silver layer was formed by performing a reduction treatment on the surface of the chipboard.

CdO, Te02 and T1203 were added to AgO according to the proposed new design, at 0.3%, respectively, in the form of Cd, Te, and Tl.

Table 6 indicates at A the thickness of the silver layer on the positive electrode agglomerate and at B the importance of the reduction treatment. It also indicates the A / B ratio on the one hand for the AgO according to the new proposed design and on the other hand for the AgO conventionally used.

As we understand by considering table 6, 60

since the AgO according to the proposed new design is significantly more stable compared to conventional AgO, the silver layer on the surface of the positive electrode is thinner than in the case of a conventional AgO with the same

Table 6

reduction of a chipboard (TR616SW) with AgO according to the new design and classic AgO

AgO A B A / B

Treatment layer thickness Ag reduction

(| x) (mAh) OVmAh)

New 51 11.7 4.35

Class. 59 7.3 8.08

reduction treatment, and the closed circuit voltage of the battery cell according to the new design is lower than that of a conventional battery cell from 70 to 100 mV.

Consequently, it has been found that the closed-circuit voltage at low temperature is improved when the silver layer formed on the surface of the positive electrode of the battery cell according to the proposed new design is between 4.4 p ./mAh and 8.1 n / mAh.

The improvement effect is remarkable if we consider this example with the previously mentioned examples 6-9.

As illustrated, the particular design according to the present invention provides a bivalent silver oxide battery cell which is excellent in terms of its low temperature characteristic, its storage (or storage) characteristic. ), and its resistance to leakage characteristic. The design according to the present invention therefore has great industrial value and it is applicable to heart stabilizers (pace maker), electronic watches, cameras, electronic calculators, hearing aids, etc.

50

s

5 sheets of drawings

Claims (8)

650362 2 1. A bivalent silver oxide cell, comprising a negative electrode, a mixture constituting a positive electrode and formed mainly of bivalent silver oxide, a separator between said negative electrode and said mixture constituting a positive electrode, and an electrolyte, the said mixture constituting the positive electrode containing cadmium and tellurium. 2. The cell of claim 1, wherein said mixture constituting the positive electrode contains one or more components selected from lead, mercury, thallium, germanium, yttrium, tin, tungsten, lanthanum , rare earth elements, zinc, selenium and aluminum. 3. Battery according to claim 1 or claim 2, wherein the said mixture constituting the positive electrode has a silver layer on at least part of its outer surface. 4. Battery according to claim 1 or claim 2, wherein said mixture constituting the positive electrode is surrounded by a monovalent silver oxide layer which has a silver layer on at least part of its outer surface. 5. Battery according to one of claims 1 to 4, wherein said mixture constituting the positive electrode contains an organic bonding agent. 6. The cell of claim 5, wherein said mixture constituting the positive electrode contains components other than bivalent silver oxide and the organic binding agent in an amount of 10 to 5000 ppm. 7. A method of manufacturing the cell according to claim 3, wherein said silver layer is formed by reduction of said bivalent silver oxide of said mixture constituting the positive electrode. 8. The manufacturing method according to claim 7, wherein the relationship between the thickness A of said silver layer and the importance B of the reduction treatment is represented by 4.4 nm / mAh ^ A / B rg 8 , 1 | xm / mAh.