DE2912496A1 - CADMIUM CONNECTION AS ADDITIONAL FOR CELLS WITH TWO-VALUE SILVER OXIDE - Google Patents

Description

-Q- March 27, 1979 Gzm / Ro

UNION CARBIDE CORPORATION, 270 Park Avenue, New York, N.Y. 10017, U.S.A.

Cadmium compound as an additive for cell * · with bivalent Silver oxide

The present invention relates to an alkaline silver oxide cell, which uses a positive electrode containing divalent silver oxide and which uses a smaller one Amount of a cadmium compound, e.g. cadmium oxide, is added to the positive electrode and / or the electrolyte in order to achieve the to improve the chemical stability of the divalent silver that is in contact with the alkaline electrolyte. Additionally the cadmium compound can be used in an alkaline AgO / zinc cell as an over-balancing depolarizer be, uo with the complete discharge of the cell the hydrogen to essentially prevent development of the cathode.

The battery has become a primary source of energy for many portable electronic devices, e.g. radios, hearing aids, watches, Calculator and the like. In order to keep the entire electronic device as compact as possible, the electronic Devices are usually cavitated to accommodate miniature cells as their source of energy. The cavities are usually designed so that a Cell can be stored well fitting in it, whereby a

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electronic contact is made with the appropriate connections within the device. A bigger one potential problem with using high energy density cells such as an alkaline cell with divalent Silver oxide and zinc reside in that when the cell bulges, it is normally within the cavity of the device becomes wedged, sometimes causing damage to the device. If the cell bulges, it can also the seal is disturbed, whereupon the electrolyte can escape, which leads to damage to the device and / or oxygen from the atmosphere can penetrate, which can lead to uneconomical corrosion of the anode. if on the other hand, the closure of the cell is maintained, bo "a high internal gas pressure may develop which does not only causes a bulging of the cell, but possibly causes the cell to break apart.

Although divalent silver azide is a good high capacity positive active material when in alkaline cells is used, it is still quite unstable when in contact with an aqueous alkaline electrolyte. In particular, divalent silver oxide is a highly oxidizing material and, as such, can be water in an aqueous alkaline Decompose electrolytes, producing oxygen gas. In addition, divalent silver oxide releases oxygen when it decomposes to monovalent silver oxide when in contact with an aqueous alkaline electrolyte. Bivalent Silver oxide can also attack cellulose materials in the cell, e.g. the separator, whereby carbonate ions are formed

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at the expense of even more electrolyte. These are undesirable Processes because they lead to cell bulging, deterioration of its parts and operational losses.

US Pat. No. 3,853,623 discloses a method to stabilize divalent silver oxide in an alkaline silver oxide-zinc cell through the use of Gold ions, which are introduced into the alkaline electrolyte on the positive side of the cell separator, or gold oxide is added to the positive active material of the cell.

In commonly assigned U.S. Patent Application No. 891,828, which is taken over as quoted, an alkaline silver oxide cell is described in which a divalent silver oxide containing electrode is used, and an aluminum-containing additive is introduced into the cell to ensure chemical stability of the divalent silver oxide when it is in contact with the alkaline electrolyte of the cell.

It is an object of the present invention to provide a divalent silver oxide cell which incorporates the formation an internal gas pressure as low as possible in order to effectively reduce distortion of the housing of the cell.

It is another object of the present invention to provide a divalent silver oxide cell in which a cadmium compound, e.g. cadmium oxide, is introduced into the electrolyte of the cell and / or into the positive electrode in order to

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to effectively control the formation of gas pressure within the cell and thereby effectively reduce the distortion of the housing of the cell
to eliminate.

It is another object of the present invention to provide a cadmium compound, e.g. Cadmium oxide, to be introduced into a cell with divalent silver oxide to chemically stabilize the divalent silver oxide when it is in contact with the aqueous electrolyte of the cell.

It is another object of the present invention to provide a cadniium compound, E.g. cadmium oxide, to be introduced into a cell with divalent silicon oxide / zinc as an overcompensating depolarizer, to prevent hydrogen evolution when the cell is completely discharged to effectively prevent from the cathode.

The present invention relates to a silver oxide cell
a negative electrode, an aqueous alkaline electrolyte, a positive electrode made of a larger proportion of divalent silver oxide and a separator between the negative and the positive electrode, characterized in that a smaller amount of a cadmium compound, for example cadmium oxide in the positive electrode and / or in the Electrolyte of the cell is introduced to improve the stability of the divalent silver oxide-containing electrode in contact with the aqueous alkaline electrolyte.

In this context, a positive electrode or means Silver oxide electrode an electrode in which the active cathode material is divalent silver oxide (AgO) or an electrode,

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in which the main active material is divalent silver oxide along with an amount (below 50% by weight) of monovalent silver oxide (Ag ₂ P) and / or some other electrochemically active positive material.

The cadmium compound, e.g., cadmium oxide, can be added to the solid positive electrode and / or in the electrolyte to be resolved. The cadmium compound that is attached to the positive electrode can either be mixed with the bivalent Silver oxide are mixed or introduced within the crystallites of the divalent silver oxide by joint precipitation or absorption during synthesis. The mixing of the cadmium compound and the bivalent one Material consisting of silver oxide has the advantage of greater flexibility with regard to the choice of the divalent silver oxide in terms of particle size, purity and the like.

The smaller amount of the added cadmium compound for use in the positive electrode according to the invention in order to improve the stability of the divalent silver oxide when it is in contact with the aqueous alkaline electrolyte of the cell should be between about 0.01 and about 5% , based on the dry weight of the divalent silver oxide in the positive electrode, preferably between about 0.1 and about 0.3% by weight based on the dry weight of the divalent silver oxide in the positive electrode. An amount of the cadmium compound less than, for example, about 0.01% by weight would not provide enough material to

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to effectively improve the stability of the divalent silver oxide material when it is in contact with the aqueous alkaline Electrolyte is available. When an amount of the cadmium compound greater than, for example, 5% by weight is added to the positive electrode is, the stability of the divalent silver oxide is not further increased when it is in contact with the aqueous alkaline electrolyte.

The cadmium compound of the invention is added to the electrolyte according should, in an amount between about 0.0001 wt -% are added up to saturation of the electrolyte with the cadmium compound.. For example, if a 33% potassium hydroxide solution is used, the upper limit is about 0.00125% based on the weight of the electrolyte. If the amount of cadmium oxide is less than, for example, about. Is $ 0.0001, there is insufficient material to improve the stability of the divalent silver oxide material when it is in contact with the aqueous alkaline electrolyte.

Cadmium oxide cannot just be used as a stabilizer but also in larger quantities from about 5 to about 25% by weight of the dry ingredients of the positive Electrode as an overbalance depolarizer in a cell with divalent silver oxide. A The overbalance depolarizer is that part of the positive electrode that is in excess of the stoichiometric amount is present to balance the negative electrode (to balance the negative electrode). The purpose of this excess amount is to increase the capacity of the positive

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To reinforce the electrode sufficiently in order to generate hydrogen when the cell is completely discharged (anode-limited) to prevent the cathode. Like divalent silver oxide, a cadmium compound such as cadmium oxide has limited solubility in alkaline media, it charges at a positive potential (relative to hydrogen) and its volumetric Energy density is high enough that the total energy density of the silver oxide / anode system is not impaired. As an excess substitute for divalent silver oxide, there is an advantage in lower cost and also in being chemical stability imparted to the divalent silver oxide material when in contact with the aqueous alkaline electrolyte stands.

It is also within the scope of the present invention to additionally add zinc oxide or aluminums to the electrolyte and / or Zinc oxide or aluminum oxide of the positive electrode. The zinc oxide and the alumina can add to the electrolyte in the area between about 0.5 and about 5 percent by weight based on the weight of the electrolyte. When zinc oxide and Aluminum oxide are added to the positive electrode, so they can be in an amount between about 0.5 and about 5 or approximately 0.001 and approximately 0.1% by weight are added, based on the dry weight of the divalent silver oxide in the positive electrode. The addition of zinc oxide was found to be more desirable than the addition of alumina. Surprisingly, the combination of cadmium oxide results in the positive Electrode and zinc oxide or alumina in the electrolyte to a synergistic effect on the stability of the two-

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valuable superoxide when in contact with the aqueous alkaline Electrolyte is available.

It is also within the scope of the present invention to add a minor amount of an active positive mixture Add stabilizer, a flux and / or a lubricant to the physical properties of the active positive Mixture continues to change, namely in terms of shaping, to make electrodes of different sizes and different Type. Examples of such additives are ethylene bis-stearamide, zinc stearate, lead stearate, calcium stearate and the same.

The silver oxide electrode according to the invention can be in an aqueous Zeilsystem can be used in which an anode made of zinc, Cadmium, indium or the like is used. The one so selected A pair of electrodes can be used with an electrolyte that is compatible with it, preferably an alkaline one Electrolytes. Examples of suitable electrolytes are aqueous solutions of alkaline earth metal hydroxides, e.g., strontium hydroxide and alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide and cesium hydroxide. Together compatible mixtures of the compounds listed above can be used. The electrode according to the invention should preferably be porous so that the walls of the pores and voids of the electrode are wetted by the electrolyte can be.

909840/0834

- Jf -

EXAMPLE I

Some lots of test cells were made, being at each positive pellet containing divalent silver oxide was used at a density of 90 grams per cubic inch, one negative electrode made of zinc and an electrolyte made of 33% KOH. The positive electrode was in a cathode collector beeher with a zinc shield placed between the inner surface of the cup and the positive pellet (see U.S. Patent 3,920,478). Then one out of two Dividing existing separator, which consists of a cellulosic barrier film and an absorption layer and a Having gold layer on the side adjacent to the cathode applied to the top of the positive pellet; then followed by the zinc electrode. An anode cup that holds the zinc electrode contained, was then placed over the Rthodenbecher and on locked conventionally.

The exact components of the positive electrode and any additives to the electrolyte are shown in Table i.

The cells were stored for three months on different ones Temperature conditions. The cells were then measured for bulge and the results for each test item were averaged; they are shown in Table 2 along with the maximum bulge observed in each item became. In addition, the operating time up to a voltage cutoff of 1.3 volts was observed; the results are also listed in Table 2.

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• feAgO ^ Ag ₂ O additive - 10 ι - Other ^ Others electrolyte ZnO ^ Addition 80 19.0. TABLE LE 1 EAA 1.0 NaAlOp η 18.9 CdO cathode η η additive _ test ZnO Post η 16.0 η ^ Addition Art. π π - _ _ 1 η 19.65 η SW Pb.Str. 0.25 ZnO - Γ « η 16.75 Il ο, ι at η η KAlO ₀ _ ι? π 19.0 - mixture EAA 1.0 _ 2 _ 3 η 18.9 CdO 3.0 π η η - _ Po ο, ι ti W W ς ■ η 16.0 η 3.0 π π η _ _ O 6th η 18.9 η -. - Il ' η 1.0 7th η If It 0.1 at π π _ 1.0 O 79.96 19th Cd-Ver mixture It Il ZnO A) 8th η binding 3.0 It NaAlO ₀ 9 η η Il 0.1 ti Il It 2 5.0 ■ Ρ 10 η π η ο, ι It ti It 1.0 11 78.98 π π 0.041 With η It 80 It - precipitation η It 1.0 12th π 19th - Il It EAA 1.0 13th η Il - H π Il η 1.0 14th η π - 1.02 ti . · Η It 1.0 15th η 18.9 CdO - - η η 16 - 17th - - 18th - - 19th 0.1 adm.

- 11 -

test % AgO $ Ag _o O additive CdO - 11 - 3 Art 1 Other ^ Others electrolyte ^ Addition Post 78.98 19th Cd-Ver »R T A B; ELLE With EAA 1.0 5.0 20th binding Il (Port setting) precipitation additive η ti dd It cathode ti If It ZnO 1.0 21st 80 18.9 ti a dm. Il dd dd 22nd η Il Cd-Ver ^ Addition It dd dd NaAlO ₉ ti 25th η dd binding 1.02 ti dd It KAlOp 5.0 ο 24 π 18.5 dd dd Il It .ZnO ^& 2 ^C It It ti, !? It dd It If 1.0 P ⁰ 96 79.92 19th η 0.1 With ft dd - 2? it dd precipitation ZnO ο η π - dd Il ti ti _ 1.0 ■ ~ · 28 Il ti 0.5 dd ti ti Il 29 Il It reDolymerei π dd dd η KAlO ₉ 5.0 10 79.44 Il 0.08 ti It Il ZnO ^A 1.0 33 80 19th H dd η dd 32 = Lead stearate κ dd Pb. St. = Ethylene η - EAA -Acrylic acid dd 0.56 -

- 12 -

• fs · ta

Test-
Post Ambient ~ Ur V IAJ.
maxi- by- T A - 12 - 1.0 45 by- 2 by- 54 ° C 16.5 Operating U ν »JLU SJ Is X
by- . times BELLE 0.0 sehnittl. maxi- 1.5 duration (hours) 1 sehnittl 0.5. * Expansion after 0.5 3.9 average times 2.0 332 2 0.1 0.0 34 ° C 0.0 0.6 3 months 8.2 1.5 332 3 -0.1 0.0 max χ- 0.5 1.0 ⁰ C 0.6 2.0 327 4th -0.2 0.5 average times 1.0 0.8 maxi 0.5 3.0 324 5 0.0 0.5 0.8 1.0 0.6 times 1.1 5.0 338 6th 0.0 0.0 -0.4 0.5 1.8 5.0 1.2 3.5 324 O 7th -0.2 0.5 -0.2 1.0 2.7 1.5 2.3 325 8th 0.0 0.0 -0.2 1.5 1.6 1.0 3.4 4.5 319 do 9 -0.2 1.0 0.1 1.0 0.9 2.0 ρ o
^ t Λ 4m * 4.0 316 10 0.2 1.0 0.5 0.5 1.6 1.5 2.5 341 11 0.2 0.5 0.2 ι, ο 1.7 3.0 2.4 4.0 319 ο 12th 0.0 0.0 0.1 0.6 4.0 3.5 3.5 324 Po 13th -0.4 1.5 0.2 2 * 5 2.4 2.5 1.8 19.5 316 ο » 14th 0.3 0.0 0.9 £, 0 1.4 1.5 2.6 3.5 324 Ψ 15th -0.3 1.0 0.2 2.0 5.4 2.5 3.3 4.5 317 16 0.1 1.0 0.2 1.5 2.4 2.5 11.7 3.5 17th 0.3 ι, ο 0.2 3.0 2.2 2.0 2.6 4.0 _ 18th 0.4 1.0 -0.4 2.8 3.5 3.0 _ 19th 0 _s 4 1.0 1.1 2.5 2.6 - 0.4 0 ^? , 9 7.0 2.4 0.4 4.0 0.8 4.0 1.1 4.0 4.0

- 13 -

Oo

to

f ¹

- 13 -

TA BELLE 2 (continued)

»Bulge after 5 months

Test- Ambient maxi- 34 by- ⁰ C 45 by- ⁰ C maxi- 54 by- ⁰ C maxi- Operating Post temperature . times average maxi- average . times average . times duration * ^ hours) by- 0.0 . 0.1 . times -0.4 1.5 262 average 0.5 0.0 0.5 1.6 2.0 2.1 3.0 316 ? 0 -0.4 0.5 1.1 0.5 1.0 2.5 2.0 2.5 • Si -0.2 1.0 0.2 2.5 0.4 2.0 1.7 2.0 22nd 0.2 -0.5 -0.2 1.0 -1.4 -0.5 -0.3 1.0 25th 0.0 0.5 0.1 i, 5 0.9 2.5 1.7 2.5 2 ^ -1.4 0.5 0.0 1.5 1.2 3.0 1.4 2.5 25th 0.0 1.0 0.7 1.0 1.8 2.5 2.1 2.5 26th -0.1 0.5 0.2 1.5 2.0 3.5 2.0 3.0 27 0.0 0.5 0.1 1.0 1.2 3.0 1.5 2.5 2S -0.2 0.0 -0.1 1.0 0.6 3.0 0.9 2.0 29 -0.3 0.5 0.4 0.5 0.6 4.0 1.2 2.0 3C -0.4 1.0 2.1 1.0 5.6 9.5 7.7 14.0 316 31 -0.1 2.5 0.5

ο »

the average bulge and the maximum bulge are in 0.001 inch increments specified

Discharge through a 3K ohm resistor up to a final voltage of 1.3 volts

a negative bulge and negative numerical values in the table relate on a decrease in the usr cell height, which sometimes occurs during storage

- 14 -

ti?

m g rn σ

The data shown in Table 2 show that according to the teachings of the invention an added cadmium compound with or without Zinc oxide and additives containing aluminum are used effectively can be used to stabilize divalent silver oxide when it is in contact with the aqueous alkaline electrolyte stands j uia to reduce the bulging of the cell. As from the Data also shows the combination of a cadmium compound results in the positive electrode and zinc oxide or alumina in the electrolyte to form a synergistic effect Effect on the stability of the divalent silver oxide in contact with the aqueous alkaline electrolyte. That means, that the addition of a cadmium compound in the positive Electrode and zinc oxide or alumina in the electrolyte reduced the bulge more than either Material on its own. One recognizes this when, for example the test item 23 with item 16, 1? and 19 for the Zin addition to the electrolyte compares and for the addition of aluminate to the electrolyte by comparing item 22 with items 16, 18 and 19.

EXAMPLE II

Several lots of cells to be tested were made as in Example I, except that the cathode and electrolyte composition as shown in Table 3. In the The data shown in Table 3 demonstrate the benefits of adding the cadmium compound in reducing bulging of the cell, as already emerged from Example I. Both Example I and Example II show that the admixed Cadmium compound gives better results in controlling the Bulge results as that obtained by coprecipitation. Cadmium compound.

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- 15 TABLE

test
Post cathode
additive additive electrolyte
additive ZnO ** Bulging after 4 months maxi
times*** 4Ϊ > ° c 54 « ³ C Art ZnO Ambient
temperature
*by-
average 1
1
1
-1 * Qurcii-
Schnitü maxi—
. times*** *by-
Schnitü. maxi—
times*** 1
2
A. 1% Cd-Vea? -
binding
Vfo "
1% " Ifo
If ₀ ZnO • H O Ol Ol
B. O 5
3
3 6th
3
2
3 10
5-
5 11
5
5
5 tP
O
O K 1.3% " With-
Solution
With-
FILLING
With-
incidental ifo NaAlO ₀ O 1 1 1 1 1 O
Po Vfo CdO With- 1% O -1 3 3 5 5 υ ¹ 7th 1% CdO At-
mixture 1% -2 2 2 _{4th 4th} At-
mLschuag

3! ο

2:

is

- 16 -

f ABELL E "(continued)

fixed-

ϊι Aiisbaitcirang ^ after 3 months

43 *by- ⁰ C 54 ■ eh— 5 ⁰ C solmittl • maxi = average 0 maxi 4.7 . times*** 8th, 5 times*** 2.9 egg 5, 5 11.0 3.2 4.0 8th 4.0 2.7 5.5 3, 2 4.5 2.1 4 ₉ 0 2, 13.0 p K 3.0 5 4.5 3.0 4.0

flie Eatlaofie "bestancl au 100% from AgO to HXelTfcroiyt was 33% potassium hydroxide solution

° a © negative bulge and negative number © »values in the table refer to a decrease in holes or cells, which also occurs during storage.

* maximum rotational speed during the specified time period ** the diarelastic sectional extent and the maximum extent are in 0.001 inch increments

given,
# ** maximum attendance of any single cell belonging to a particular test item

Claims (26)

Claims A silver oxide cell with a negative electrode, one in aqueous alkaline electrolyte, a positive electrode made of a larger proportion of divalent silver oxide and a separator between the negative electrode and the positive electrode characterized by the addition of Cadmium oxide in the positive electrode, to the stability of the divalent silver oxide containing electrode in contact To improve with the aqueous alkaline electrolyte, the cadmium oxide is in the positive electrode in one Amount present between about 0.01 and about 0.5 weight percent based on the dry weight of the divalent Silver oxide in the positive electrode. 2. The silver oxide according to claim 1, characterized in that cadmium oxide in an amount between about 0.1 and about 0.3 wt -% is present, based on the dry weight of the divalent silver oxide in the positive electrode.. 3. The SilTberoxidzelle according to claim 1, characterized in that the positive electrode is less than 50 wt -% containing monovalent silver oxide, based on the dry weight of the divalent silver oxide in the positive electrode.. 4 »The silver oxide according to claim 3» characterized in that the Cadmiumoxid'der positive electrode in an amount between about 0.0i to about 0.3 wt -% is present, based on the dry weight of the divalent silver oxide. in the positive electrode. - 18 - 909840/0834 5. The silver oxide cell according to claim k, characterized in that the Cadmiuraoxid in an amount between about 0.1
and about 0.3% by weight based on the
Dry weight of the divalent silver oxide in the positive electrode. 6. The silver oxide cell according to claim 1, characterized in that the positive electrode has smaller amounts of zinc oxide
or contains alumina. 7. The silver oxide cell according to claim 1, characterized in that the aqueous alkaline electrolyte is a smaller amount Contains zinc oxide or alumina. 8. The silver oxide cell according to claim 1, characterized in that the positive electrode has a smaller amount of a
Contains material which is selected from the group consisting of ethylene bis-stearamide, zinc stearate, lead stearate
and calcium stearate. 9. The silver oxide cell according to claim 1, characterized in that the negative electrode is selected from the group
consisting of zinc, cadmium and indium. 10, The silver oxide cell according to claim 1, characterized in, that the negative electrode is zinc. - 19 - 909840/0834 11. The silver oxide cell according to claim 1, characterized in that the negative electrode is zinc and the electrolyte is made of aqueous potassium hydroxide. 12. The silver oxide cell according to claim i, characterized in that that the negative electrode is zinc and the electrolyte consists of aqueous sodium hydroxide. 13. A silver oxide cell with a negative electrode, a aqueous alkaline electrolyte, a positive electrode made of a larger amount of divalent silver oxide and a separator between the negative electrode and the positive electrode, characterized by the insertion of Cadmium oxide in the electrolyte to ensure the stability of the divalent Silver oxide containing electrode in contact with the aqueous alkaline electrolyte to improve the Cadmium oxide is in the ElektiriLyten in an amount between about 0.0001 wt .-% based on the weight of the electrolyte Present until the electrolyte is saturated with cadmium oxide. 14. The silver oxide according to claim 13, characterized in that the positive electrode is less than 50 wt -% containing monovalent silver oxide, based on the dry weight of the divalent silver oxide in the positive electrode.. 15. The silver oxide cell according to claim 13, characterized in that the aqueous alkaline electrolyte is a smaller amount Contains zinc oxide or alumina. - 20 - 909840/0834 16. The silver oxide cell according to claim 13> characterized in that the negative electrode is selected from the group consisting of zinc, cadmium and indium. 17. The silver oxide cell according to claim 13, characterized in that «iie negative electrode is zinc. 18. The silver oxide cell according to claim 13, characterized in that the negative electrode is zinc and the electrolyte is made of aqueous potassium hydroxide or sodium hydroxide. 19. The silver oxide cell according to claim 13, characterized in that that the positive electrode contains a smaller amount of cadmium oxide. 20. The silver oxide cell according to claim 19 »characterized in that cadmium oxide in the positive electrode in an amount present between about 0.01 and about 0.5 weight percent based on the dry weight of the divalent silver oxide in the positive electrode. 21. The silver oxide cell according to claim 19, characterized in that that the positive electrode is less than 50% by weight monovalent Silver oxide contains, based on the weight of the dry components of the positive electrode. 22. The silver oxide cell according to claim 21, characterized in that that the cadmium oxide is present in the positive electrode in an amount between about 0.01 and about 0.5 weight percent based on the dry weight of the divalent silver oxide in the positive electrode. - 21 - 909840/0834 23. The silver oxide cell according to claim 19, characterized in that that the positive electrode contains a minor amount of a material selected from the group consisting of Ethylene bis-stearamide, zinc stearate, lead stearate and calcium stearate. 24. The silver oxide cell according to claim 19 »characterized in that that the negative electrode is selected from the group consisting of zinc, cadmium and indium. 25. Bie silver oxide cell according to claim 20, characterized in that the negative electrode is zinc and the electrolyte is made of
aqueous potassium hydroxide. 26. A silver oxide cell with a negative electrode, a
aqueous alkaline electrolyte, a positive electrode
from a larger proportion of divalent silver oxide and
a separator between the negative electrode and the
positive electrode, characterized by the addition of
Cadmium oxide in an amount between about 5 and about
$ 25 based on the weight of the dry ingredients
positive electrode, the aqueous alkaline electrolyte containing a minor amount of zinc oxide or alumina. 909840/0834