CA1042979A - High drain rate, primary alkaline cell having a divalent silver oxide/monovalent silver oxide depolarizer blend coated with a layer of silver - Google Patents
High drain rate, primary alkaline cell having a divalent silver oxide/monovalent silver oxide depolarizer blend coated with a layer of silverInfo
- Publication number
- CA1042979A CA1042979A CA265,958A CA265958A CA1042979A CA 1042979 A CA1042979 A CA 1042979A CA 265958 A CA265958 A CA 265958A CA 1042979 A CA1042979 A CA 1042979A
- Authority
- CA
- Canada
- Prior art keywords
- blend
- depolarizer
- silver oxide
- pellet
- cell
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/54—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of silver
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M6/00—Primary cells; Manufacture thereof
- H01M6/04—Cells with aqueous electrolyte
- H01M6/06—Dry cells, i.e. cells wherein the electrolyte is rendered non-fluid
- H01M6/12—Dry cells, i.e. cells wherein the electrolyte is rendered non-fluid with flat electrodes
Landscapes
- Chemical & Material Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Manufacturing & Machinery (AREA)
- Engineering & Computer Science (AREA)
- Inorganic Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Primary Cells (AREA)
- Cell Separators (AREA)
- Luminescent Compositions (AREA)
- Adhesives Or Adhesive Processes (AREA)
- Developing Agents For Electrophotography (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A high drain rate, primary alkaline cell comprising a negative electrode, a divalent silver oxide (AgO)/monovalent silver oxide (Ag2O) depo-larizer blend, a separator between said negative electrode and depolarizer blend, and an alkaline electrolyte consisting essentially of potassium hydro-xide. The surface of the depolarizer blend adjacent to the separator is coated with a layer of silver. The reduced surface layer of the depolarizer provides improved stability of the depolarizer blend in the alkaline electrolyte, and it provides the cell with a single voltage plateau during discharge. The cell is characterized by a maximum open circuit voltage of about 1.75 volts. The surface of the depolarizer blend can be reduced to form the silver layer ei-ther prior to being placed in the cell container or after the blend is consoli-dated in the container. The amount of divalent silver oxide present in the depolarizer blend is critical, and the blend may contain up to about 70% by weight of divalent silver oxide and still achieve a single voltage plateau during discharge. The cell has a high drain rate capability whereby is can be pulsed, said cell being capable of providing a flash amperage greater than an average of 0.20 amperes per square centimeter of cell cross-sectional area.
A high drain rate, primary alkaline cell comprising a negative electrode, a divalent silver oxide (AgO)/monovalent silver oxide (Ag2O) depo-larizer blend, a separator between said negative electrode and depolarizer blend, and an alkaline electrolyte consisting essentially of potassium hydro-xide. The surface of the depolarizer blend adjacent to the separator is coated with a layer of silver. The reduced surface layer of the depolarizer provides improved stability of the depolarizer blend in the alkaline electrolyte, and it provides the cell with a single voltage plateau during discharge. The cell is characterized by a maximum open circuit voltage of about 1.75 volts. The surface of the depolarizer blend can be reduced to form the silver layer ei-ther prior to being placed in the cell container or after the blend is consoli-dated in the container. The amount of divalent silver oxide present in the depolarizer blend is critical, and the blend may contain up to about 70% by weight of divalent silver oxide and still achieve a single voltage plateau during discharge. The cell has a high drain rate capability whereby is can be pulsed, said cell being capable of providing a flash amperage greater than an average of 0.20 amperes per square centimeter of cell cross-sectional area.
Description
;2979 In the packaged power industry7 there is an ever increasing emphasis upon the development of high capacity, small volume electric cellsO The follo-wing is a comparison of the capacity and voltage for some active materials currently used in commercially available cells:
Active E~ vs. Zn in Capacity MaterialAlkaline Electrolyte ~ amp-hr./cc HgO 1-35v- 248 2.76 Ag20 1.60v. 232 1.67 Ag~ 1.82v. 432 3.22 Divalent silver oxide (AgO) is an excellent high capacity battery active material, but it has two properties which have limited its use as a battery active material. During the discharge of a battery employing a diva-lent silver oxide positive active material, the initial voltage is at the higher divalent voltage level (1082v. vs. Zn in alkaline electrolyte) Until substantially all of the AgO is converted to Ag20, and thereafter, the dischar-ge continues at the lower monovalent voltage level (1060v. vsO~n in alkaline electrolyte). This two plateau voltage level during discharge cannot be tolerated b~ many types of battery operated equipment.
Another problem encountered when using divalent silver oxide as a depolarizer (positive active material) is its lack of stability when in con-tact with aqueous alkaline solutions. It is well known that divalent silver oxide evolves oxygen when in contact with aqueous alkaline solutions, and this gassing phenomenon causes self-discharge of the divalent silver oxide~
converting it to monovalent silver oxide or metallic silverO Divalent silver oxide cannot be used as the positive active material in hermetically sealed cells because of this instability in alkaline solutions and the consequent hazard of pressure build-up and possible cell rupture.
The problem of the two plateau voltage level during the electrical discharge of divalent silver oxide has previously been overcome by the in~entions disclosed in United States Patent Numbers 3,615,858 and 3,655,450 issued to Luis Soto-Krebs. These patents disclose a battery having a positive electrode comprising a principal active material (e.g. divalent silver oxide) and a secondary active material (e.g. monovalent silver oxide) whose discharge product is readily oxidized by the principal active material in the presence of alkaline electrolyte, and wherein khe sole electronic path for discharge of the principal active material is through the secondary active material.
The battery invented by Soto-Krebs ischaracterizedthroughout discharge by the potential of the secondary active material (Ag20) vs. the negative electrode in the alkaline electrolyte. The battery has the advantage of a single voltage level during electrical discharge and also the increased capacity provided by the divalent silver oxide positive acti~e materialO
The problem of the divalent silver oxide instability has been over-come by the inventions disclosed in United States Patent Numbers 3,476,610 and 3~484~295 issued to Luis Soto-Krebs and Robert Dawson. These patents disclose a battery having a positive electrode comprising a principal active material (e.g. divalent silver oxide) and a secondary active material (e.g.
monovalent silver oxide) employed as a substantially electolyte-impermeable layer interposed between the principal active material and the battery compo-nents containing the electrolyte. This construction isolates the principalactive material from contact with the electrolyte until the secondary active material is discharged, thereby providing improved stand or shelf lifeO
It is the general object of this invention to provide a high drain rate~ primary alkaline cell having a divalent silver oxide/monovalent silver oxide depolarizer blend which is stable in the potassium hydroxide alkaline electrolyte and which cell is characterized by a single voltage plateau during discharge. Another object of the invention is to provide a high drain rate~
primary alkaline cell, particularly of the "button cell" construction, which has increased capacity per unit weight and volume compared to a cell employing ~4Z979 only monovalent silver oxide as the positive active material. A further ; object is to provide a high drain rate, primary alkaline cell having a posi-tive electrode comprising a blend of divalent silver oxide and monovalent silver oxide which will utilize the capacity of both of these active materials and having a maximum open circuit voltage ~vs. Zn in alkaline electrolyte) of about 1.75 volts. A still further object is to provide a novel method of manufacturing a divalent silver oxide/momovalent silver oxide depolarizer blend coated with a layer of silver.
According to one aspect of the present invention, there is provided a high drain rate, primary alkaline cell comprising a negative electrode, a divalent silver oxide/monovalent silver oxide depolarizer blend, a separator between said negative electrode and the depolarizer blend, and an aqueous potassium hydroxide electrolyte, said depolarizer blend containing up to about 70% by weight of divalent silver oxide, and a substantially continuous and electrolyte permeable layer of silver on the surface of the depolarizer blend adjacent to the separator, whereby the cell is characterized by the stability of the depolarizer blend in the potassium hydroxide electrolyte, a maximum open circuit voltage of about 1.75 volts, a single voltage plateau during discharge and is capable of providing a flash current greater than an average of 0.2 amps per square centimeter of cell cross-sectional area.
Quite unexpectedly, it has been found that the depolarizer blend can be discharged at a single voltage plateau without restricting the elec-tronic path to monovalent silver oxide; however, it is essential that the silver layer on the surface of the depolarizer blend be present. The layer of silver on the depolarizer blend is essential to achieve a single voltage plateau during discharge of the cell, and it also provides improved stability of the depolarizer blend in the potassium hydroxide electrolyte.
The layer of silver may be formed by treating the surface of the depolarizer blend with a strong reducing agent such as hydrazine or formalde-hyde.
The surface of the depolarizer blend can be reduced either priorto being placed in the cell container, or preferably, after the blend is ~Yl ~3~
~
., . ' ~ b ~ . ,'" ', ' ' ' ~ ~ , - /
consolidated in the container.
Thus, according to one aspect of the method of ~he present invention, there is provided a method for manufacturing the depolarizer blend used in the primary alkaline cell of the invention comprising forming the depolarizer blend comprising divalent silver oxide and monovalent silver oxide, compressing the blend to form a pellet, placing the pellet in a cathode container, consolidating the pellet in the container by compression, and treating the consolidated pellet/cathode container component with a strong reducing agent for a period of time sufficient to reduce the surface of the depolarizer blend to metallic silver.
According to another aspect of the method of the present invention, there is provided a method for manufacturing the depolarizer blend used in the primary alkaline cell of the invention comprising forming the depolarizer blend comprising divalent silver oxide and monovalent silver oxide, compress-ing the blend to form a pellet, treating the pellet with a strong reducing agent for a period of time sufficient to reduce the surface of the depolarizer blend to metallic silver, placing the pellet with the reduced surface in a cathode container, and consolidating the pellet with the reduced surface in the cathode container by compression.
-3a-297~
:, The high drain rate, primary alkaline cells of this invention are particularly useful as power sources for elec~ronic watches, and they are manufactured in the "button cell" construction for use in small electric ; devices such as watches and hearing aids. The cells have the required single voltage plateau discharge characteristics and also stability of the depolari-zer blend in potassium hydroxide electrolyte without incorporating special additives, such as those disclosed in United States patent Number 3,650,832.
The primary alkaline cells have substantially increased electrochemical capa-city over that supplied by cells using a monovalent silver oxide depolarizer.
These cells also have improved high drain rate capability required for pulsing to activate a light emitting diode.
The above and other objects and advantages of this invention will be more fully described in the description of the preferred embodiment, parti-cularly when read in conjunction with the accompanying drawing.
Pigure 1 is a cross-sectional view of the high drain rate, primary alkaline cell of this invention, in completely assembled condition.
This invention comprises a highdrain rate, primary alkaline cell having a divalent silver oxide (AgO)/monovalent silver oxide (Ag20) depolarizer blend (cathode) coated with a layer of silver, a negative electrode (anode),
Active E~ vs. Zn in Capacity MaterialAlkaline Electrolyte ~ amp-hr./cc HgO 1-35v- 248 2.76 Ag20 1.60v. 232 1.67 Ag~ 1.82v. 432 3.22 Divalent silver oxide (AgO) is an excellent high capacity battery active material, but it has two properties which have limited its use as a battery active material. During the discharge of a battery employing a diva-lent silver oxide positive active material, the initial voltage is at the higher divalent voltage level (1082v. vs. Zn in alkaline electrolyte) Until substantially all of the AgO is converted to Ag20, and thereafter, the dischar-ge continues at the lower monovalent voltage level (1060v. vsO~n in alkaline electrolyte). This two plateau voltage level during discharge cannot be tolerated b~ many types of battery operated equipment.
Another problem encountered when using divalent silver oxide as a depolarizer (positive active material) is its lack of stability when in con-tact with aqueous alkaline solutions. It is well known that divalent silver oxide evolves oxygen when in contact with aqueous alkaline solutions, and this gassing phenomenon causes self-discharge of the divalent silver oxide~
converting it to monovalent silver oxide or metallic silverO Divalent silver oxide cannot be used as the positive active material in hermetically sealed cells because of this instability in alkaline solutions and the consequent hazard of pressure build-up and possible cell rupture.
The problem of the two plateau voltage level during the electrical discharge of divalent silver oxide has previously been overcome by the in~entions disclosed in United States Patent Numbers 3,615,858 and 3,655,450 issued to Luis Soto-Krebs. These patents disclose a battery having a positive electrode comprising a principal active material (e.g. divalent silver oxide) and a secondary active material (e.g. monovalent silver oxide) whose discharge product is readily oxidized by the principal active material in the presence of alkaline electrolyte, and wherein khe sole electronic path for discharge of the principal active material is through the secondary active material.
The battery invented by Soto-Krebs ischaracterizedthroughout discharge by the potential of the secondary active material (Ag20) vs. the negative electrode in the alkaline electrolyte. The battery has the advantage of a single voltage level during electrical discharge and also the increased capacity provided by the divalent silver oxide positive acti~e materialO
The problem of the divalent silver oxide instability has been over-come by the inventions disclosed in United States Patent Numbers 3,476,610 and 3~484~295 issued to Luis Soto-Krebs and Robert Dawson. These patents disclose a battery having a positive electrode comprising a principal active material (e.g. divalent silver oxide) and a secondary active material (e.g.
monovalent silver oxide) employed as a substantially electolyte-impermeable layer interposed between the principal active material and the battery compo-nents containing the electrolyte. This construction isolates the principalactive material from contact with the electrolyte until the secondary active material is discharged, thereby providing improved stand or shelf lifeO
It is the general object of this invention to provide a high drain rate~ primary alkaline cell having a divalent silver oxide/monovalent silver oxide depolarizer blend which is stable in the potassium hydroxide alkaline electrolyte and which cell is characterized by a single voltage plateau during discharge. Another object of the invention is to provide a high drain rate~
primary alkaline cell, particularly of the "button cell" construction, which has increased capacity per unit weight and volume compared to a cell employing ~4Z979 only monovalent silver oxide as the positive active material. A further ; object is to provide a high drain rate, primary alkaline cell having a posi-tive electrode comprising a blend of divalent silver oxide and monovalent silver oxide which will utilize the capacity of both of these active materials and having a maximum open circuit voltage ~vs. Zn in alkaline electrolyte) of about 1.75 volts. A still further object is to provide a novel method of manufacturing a divalent silver oxide/momovalent silver oxide depolarizer blend coated with a layer of silver.
According to one aspect of the present invention, there is provided a high drain rate, primary alkaline cell comprising a negative electrode, a divalent silver oxide/monovalent silver oxide depolarizer blend, a separator between said negative electrode and the depolarizer blend, and an aqueous potassium hydroxide electrolyte, said depolarizer blend containing up to about 70% by weight of divalent silver oxide, and a substantially continuous and electrolyte permeable layer of silver on the surface of the depolarizer blend adjacent to the separator, whereby the cell is characterized by the stability of the depolarizer blend in the potassium hydroxide electrolyte, a maximum open circuit voltage of about 1.75 volts, a single voltage plateau during discharge and is capable of providing a flash current greater than an average of 0.2 amps per square centimeter of cell cross-sectional area.
Quite unexpectedly, it has been found that the depolarizer blend can be discharged at a single voltage plateau without restricting the elec-tronic path to monovalent silver oxide; however, it is essential that the silver layer on the surface of the depolarizer blend be present. The layer of silver on the depolarizer blend is essential to achieve a single voltage plateau during discharge of the cell, and it also provides improved stability of the depolarizer blend in the potassium hydroxide electrolyte.
The layer of silver may be formed by treating the surface of the depolarizer blend with a strong reducing agent such as hydrazine or formalde-hyde.
The surface of the depolarizer blend can be reduced either priorto being placed in the cell container, or preferably, after the blend is ~Yl ~3~
~
., . ' ~ b ~ . ,'" ', ' ' ' ~ ~ , - /
consolidated in the container.
Thus, according to one aspect of the method of ~he present invention, there is provided a method for manufacturing the depolarizer blend used in the primary alkaline cell of the invention comprising forming the depolarizer blend comprising divalent silver oxide and monovalent silver oxide, compressing the blend to form a pellet, placing the pellet in a cathode container, consolidating the pellet in the container by compression, and treating the consolidated pellet/cathode container component with a strong reducing agent for a period of time sufficient to reduce the surface of the depolarizer blend to metallic silver.
According to another aspect of the method of the present invention, there is provided a method for manufacturing the depolarizer blend used in the primary alkaline cell of the invention comprising forming the depolarizer blend comprising divalent silver oxide and monovalent silver oxide, compress-ing the blend to form a pellet, treating the pellet with a strong reducing agent for a period of time sufficient to reduce the surface of the depolarizer blend to metallic silver, placing the pellet with the reduced surface in a cathode container, and consolidating the pellet with the reduced surface in the cathode container by compression.
-3a-297~
:, The high drain rate, primary alkaline cells of this invention are particularly useful as power sources for elec~ronic watches, and they are manufactured in the "button cell" construction for use in small electric ; devices such as watches and hearing aids. The cells have the required single voltage plateau discharge characteristics and also stability of the depolari-zer blend in potassium hydroxide electrolyte without incorporating special additives, such as those disclosed in United States patent Number 3,650,832.
The primary alkaline cells have substantially increased electrochemical capa-city over that supplied by cells using a monovalent silver oxide depolarizer.
These cells also have improved high drain rate capability required for pulsing to activate a light emitting diode.
The above and other objects and advantages of this invention will be more fully described in the description of the preferred embodiment, parti-cularly when read in conjunction with the accompanying drawing.
Pigure 1 is a cross-sectional view of the high drain rate, primary alkaline cell of this invention, in completely assembled condition.
This invention comprises a highdrain rate, primary alkaline cell having a divalent silver oxide (AgO)/monovalent silver oxide (Ag20) depolarizer blend (cathode) coated with a layer of silver, a negative electrode (anode),
2~ a separator between the depolarizer blend and the negative electrode, and an aqueous potassium hydroxide solution as the electrolyte. It is essential that the surface of the depolarizer blend adjacent to the separator be coated with a layer of silver which provides improved stability of the depolarizer blend in the potassium hydroxide electrolyte and provides the cell with a single voltage plateau during discharge. The silver layer may be formed by treating the surface of the depolarizer blend with a strong reducing agent, such as hydrazine, which provides a substantially continuous and electrolyte permeable silver layer. The maximum open circuit voltage of the cell is about ~4Z979 1.75 volts, and it is preferred that the open circuit voltage be approximately 1.6 volts which is characteristic of monovalent silver oxide. The open cir-cuit voltage is measured by discharging the cell through a very high load, on the order of one to one hundred megaohms. If a cell has an open circuit vol-tage of less than about 1.75 volts, it should provide a single voltage plateau during closed circuit discharge, even at low drains, for example discharges through loads of about 100,000 to about 500,000 ohms.
In addition to the silver layer on the depolarizer blend, the amount of divalent silver oxide present in the depolarizer blend is criticalO It is preferred to have the maximum amount of divalent silver oxide and still achieve a single voltage plateau during discharge and a stable depolarizer blend. It has been determined that the amount of divalent silver oxide should not be greater than about 70% by weight of the silver oxide blend. In addition to the divalent and monovalent silver oxides, the depolarizer may also contain minor amounts of a lubricant and/or binder such as polytetrafluoroethylene or other suitable plastic binder. Ingredients may also be incorporated in the depolarizer for the purpose of providing voltage stability such as silver powder, and to insure the stability of the divalent silver oxide in the alkaline elec-trolyte~ such as gold hydroxide as disclosed in United States patent Number
In addition to the silver layer on the depolarizer blend, the amount of divalent silver oxide present in the depolarizer blend is criticalO It is preferred to have the maximum amount of divalent silver oxide and still achieve a single voltage plateau during discharge and a stable depolarizer blend. It has been determined that the amount of divalent silver oxide should not be greater than about 70% by weight of the silver oxide blend. In addition to the divalent and monovalent silver oxides, the depolarizer may also contain minor amounts of a lubricant and/or binder such as polytetrafluoroethylene or other suitable plastic binder. Ingredients may also be incorporated in the depolarizer for the purpose of providing voltage stability such as silver powder, and to insure the stability of the divalent silver oxide in the alkaline elec-trolyte~ such as gold hydroxide as disclosed in United States patent Number
3,853,623.
The negative electrode may be zinc, cadmium, indium, magnesium, aluminum, titani~ or manganese. It is preferred to use zinc active material which may be in the form of finely divided zinc particles, gelled or semi-gelled zinc particles, or a zinc foil. It is generally preferred that the zinc active material should be amalgamated regardless of the form which is usedO
Between the depolarizer blend and the negative electrode, there is placed a separator which generally comprises both an absorbent component and a barrier material. The absorbent component may be made from a cellulosic mate-rial such as matted cotton fibers or from a non-cellulosic material such as l~Z97~
microporous polyethylene. The absorbent material holds the electrolyte (gene-rally in contact with the negative active material), and a plurality of layers may be used. The barrier material may also comprise one or more layers for preventing the passage of metallic ions or dendrite growth from one electrode to the other. The barrier material may be any suitable semi-permeable material such as the regenerated cellulose material commercially available under the trademark "Cellophane", either alone or in combination with a synthetic bar-rier such as polyethylene grafted with methacrylic acid. It is preferred to use a laminated barrier material which comprises a layer of polyethylene grafted with methacrylic acid be~ween layers of Cellophane, ~trademark).
The cells of this invention utilize an alkaline electrolyte consis-ting essentially of an aqueous solution of potassium hydroxide. The electrolyte is preferably limited to an amount sufficient only to provide wetting of the cell components without establishing a liquid level of free electrolyte in the cell. The alkaline electrolyte preferably has a potassium hydroxide con-centration of at least about 3% by weight ranging up to about 50% by weight.
It may contain minor amounts of additives such as zinc oxide to inhibit dis-solution of the zinc negative active material, and other alkali metal hydro-xides, e.g. cesium, rubidium or sodium, may be substituted for minor portions of the potassium hydroxide.
A critical feature of this invention is the formation of the layer of silver on the surface of the depolarizer blend adjacent to the separator.
A substantially continuous and electrolyte permeable layer of silver may be fo~med by treating the surface of the depolarizer blend with a strong reducing agent such as hydrazine or formaldehyde solutions. Other relatively strong reducing agents such as hydrogen, metals ~zinc and iron), tin chloride, iron sulfate, sulfurous acid, oxalic acid, formic acid and hydroxylamine can also be used, provided that they are strong enough to reduce the depolarizer blend to silver within a reasonable time. When using hydrazine or formaldehyde, methanol solutions of the reducing agent are preferred and the surface of the -97g depolarizer blend is treated for several minutes, generally from about 2-6 minutes is su-fficient. A high proportions o-f AgO may require a longer reducingagent treatment. The treatment with the reducing agent is usually performed at room temperature, however~ elevated temperatures may be used especially if it is desired to accelerate the reduction. Aqueous solutions of the reducing agent can be used as well as an organic so]vent solution.
The depolarizer blend can be physically mixed, incorporating additi-ves for special purposes, and then compressed into a pellet. The entire surface of the pellet can be reduced to silver by soaking the pellet or tumblingit in the reducing agent solution. This is not a preferred method, for it was found that pieces of the compressed depolarizer pellet broke off during the reduction treatment, and in some cases there was non-uniform pellet reduction~
In addition to physical mixing, the depolarizer blend may be prepared by (1) oxidizing silver powder, ~2) reducing a portion of a divalent silver oxide active material, or (3) reducing the AgO in situ by mixing it with a reducing metal such as zinc or cadmium.
The preferred method for manufacturing the depolarizer blend com-prises (1) forming the depolarizer blend comprising divalent silver oxide and monovalent silver oxide9 (2) compressing the blend in a press to form a pellet using a pressure ranging from about 40,000 to 60,000 psi, (3) placing the pellet in the cathode container, (4) consolidating the pellet in the con-tainer by compression using a consolidation pressure ranging from about 50,000 to 70,000 psi, and (5) treating the consolidated pellet/cathode container component with the reducing agent solution. In this preferred method, the bottom and sides of the depolarizer blend pellet remain non-reduced, however, treatment with the reducing agent may be carried out prior to consolidation~
It is preferred to place a sleeve around the upper edge of the depolarizer blend, and this may be done prior to consolidating the pellet in the cathode containerO The sleeve functions as a supporting surface to protect ~he 1~)429~9 depolari~er pellet during consolidation and when the cell is sealed by crimping the upper edge of the cathode container upon the grommet molded on the edge of the anode container.
One of the principal objectives of this invention is to increase the energy density per unit weight or volume of the depolarizerO Maximum energy density would be achieved by using only divalent silver oxide depolarizer materialg but the resultant cell has two vol~age plateaus during discharge and the divalent silver oxide is very unstable in the potassium hydroxide electrolyte. It has been found that the depolarizer blend can contain a maxi-mum of about 70% by weight of divalent silver oxide and still provide a highdrain rate alkaline cell having a single voltage plateau and a stable depola-rizer. When mass producing the high drain rate, primary alkaline cells, it is generally preferred to use a depolarizer blend comprising at least about 50%
divalent silver oxide in order to insure that the cell has a single voltage plateau, satisfactory elevated temperature stability, and improved electro-chemical capacity.
; Referring now to Figure 1~ a button cell construction (10) is illus-trated~ for the high drain rate, primary alkaline cells of this invention are particularly adapted for use in this construction, and button cells were used to evaluate the divalent silver oxide/monovalent silver oxide depolari~er blendsO These button cells are of the type currently used as a power source for electronic watches, an application for which the high drain rate, primary alkaline cells having a divalent silver oxide/monovalent silver oxide depola-rizer blend coated with a layer of silver are particularly effective.
The negative electrode (anode) container (11) comprises what is commonly referred to as a "double top". Two cans are placed in physical, electrical contact with each other, with the inner can (12) being nested in the outer can (13) to form a tight friction fit. It is generally preferred to spot weld the cans together as indicated at (14) to maintain permanent ~)42~9 electrical contactc The cans may be made from nickel-plated stcel which has good corrosion resistance, however, other materials may be used and the sur-faces of the cans can be given special coatings. The "double top" anode con-tainer is pref7erred for its superior leakage prevention properties~ however~
a single top container can be used. A collar orgrommet (15) of nylon or poly-ethylene is molded onto the edge of the anode container (11) to electrically insula~e it from the depolarizer (cathode) container (16)o. The negatiue elec-trode or anode ¦17) is a zinc active material in the form of a gel or semi-gel comprising finel~ divided zinc particles, a small amount of gelling agent such as guar gum or carboxymethyl cellulose (e.gO 0.2% by weight) and a portion of the aqueous potassium hydroxide electrolyte solution.
The separator comprises an abs~rbent component (18) and a barrier material (19). It is preferred to use matted cotton fibers (commercially available under the trademark "~ebril") as the absorbent component which also contains a portion of the alkaline electrolyteO The semi-permeable barrier material comprises a layer (20) of polyethylene grafted with methacrylic acid (commercially available under the trademark "Permion") sandwiched between layers A ~ ~ ~ I/dp~
(21) of ~e~10~h~n~. The absorbent component (18) is placed in contact with the ~inc active material, and the barrier material is in contact with the silver layer (22) on the surface of the depolarizer blend (23)o The depolarizer blend or cathode (23) comprises a mixture of diva-lent silver oxide ~AgO) and monovalent silver oxide (Ag20) and additives for special effects. The depolarizer blend generally contains polytetrafluoroethy-lene as a binder and lubricant. The blend may also contain a minor amount of a gas suppressan~ such as gold hydroxide to insure the stability of the diva-lent silver oxideO The following is a preferred depolarizer blend composition:
Ingredient Amount (% by wto) Divalent Silver Oxide (AgO) 50 Monovalent Silver Oxide (Ag20) ~8.35 Polytetrafluoroethylene~ Teflon) 1.5 Gold Hydroxide - 0.15 ~q ~ e nn~ ~5 ~ 9 ~
~)4~79 The silver layer (22) is formed in situ on the depolarizer blend after it is consolidated in the cathode container (16) by immersing it in a 3% by weight hydrazine solution in methanol for about S minutes. ~hen formed in this manner~
the silver layer is substantially con~inuous and electrolyte permeableO A
sleeve (241 is placed around the upper edge of the depolarizer blend, however, this is not an essential component of the button cell constructionO If desired, the entire surface of the depolarizer blend (23) can be reduced by carrying out the reduction treatment prior to consolidation in container (16)o The high drain rate~ primary alkaline cells of this invention are specially designed and constructed as power sources for electronic watches having a light emitting diode ~IED) display. These watches require a battery which is capable of providing a high drain rate discharge in the form of pulsesO
It is essential in order to light the display for a reasonable number of p~ses that the primary alkaline cells be capable of providing a flash current greater than an average of 0.2 amperes per square centimeter of cell cross-sectional areaO In addition, the cell system must have improved stability in the pre-sence of alkaline electrolyte~ for the potassium hydroxide electrolyte requ1-red for the high drain rate capability accentuates the propensity of the divalent silver oxide to evolve gas in the presence of alkaline solutions. In some cases it may be necessary to precondition the cell before using it as a power source by short circuiting the cell for a few seconds. It has been dis-covered that this preconditioning increases the flash current of the cell and provides more uniform flash current performance.
Example 1 Primary alkaline button cells (RW 44 size having a cathode container diameter of 0.450 inches and a height ranging from about 00150 to about 0.162 inches) having the construction illustrated in Figure 1 were tested to deter-mine the effect of a silver layer placed on the depolarizer blend surface for high rate cells (35% KOH t 1% ZnO aqueous electrolyte solution)O In ~6~4~
addition to the mixture of divalent and monovalent silver oxides~ the depola-rizer blend contained 1.5% by weight of polytetrafluoroethylene and 0.15% by weight of gold hydroxide. The depolarizer blend was immersed, after consolida-tion in the cathode container, in a 3% by weight hydrazine in methanol solution for 3 minutes to f~rm the substantially continuous silver layer. The anode was a zinc blend comprising 99.8% by weight of amalgamated zinc particles (7%
mercury) and 002% by weight of guar gum gelling agent. The closed circuit voltage (CCV) was measured through a 167 ohm loadO The electrical properties and stability were recorded as the average for 30 cellsO The flash current was measured by electrically connecting a cell to a standard ammeter (having an internal resistance of about 0.015 ohms~ and determining the current flow at 0.5 secondsO The following results were recorded:
Cell Electrical Properties Expansion Flash 4 wks. at % AgO in Electro- Silver Impedance OCV CCV Current 165 F
Depolarizer lyte Layer (ohms) (volts) (volts) (amps) (mils) 40 ~OH No34.4 1085 1.28 0015 2102 40 " Yes3.4 1.60 1-55 0.69 12.5 30 " No35.7 1.85 1.15 0013 2007 30 " ~es3.0 1060 1-55 0.71 806 The superior performance and properties of the cells having a silver layer on the depolarizer blend is clearly demonstrated.
Example 2 Primary alkaline button cells (RW 44 size) having the construction illustrated in Figure 1 were made to determine the effect of varying the AgO/
Ag20 ratio in combination with and without a hydrazine reduction treatment to form a silver layer on the depolarizer blendO The hydrazine treatment consis_ ted of soaking the consolidated pellets in a sclution of 1% by weight hydra-zine in methanol, with stirring, for 3 minutes. In each of the cells, the sleeve around the depolarizer pellet was silver-platedO The electrolyte was a _ 11 --97~
40% KOH ~ 1% ~nO aqueous solution~ The following results were recorded:
Cell Electrical Properties Expansion 7 days % AgO in Silver Impedance OCV CCV(1670hms) at 165 F
Depolari7er Layer (ohms~ ~ (voltsl (mils) No 98-4 1.86 1.33 804 Yes 2.9 1.61 1.55 4.4 No 97-4 1.86 1.34 7-0 Yes 2.7 1.61 1-55 6.2 No 93.6 1.86 1.37 15.4 Yes 9.9 1.61 1.54 16.4 No 99.4 1.86 1.34 7~4 Yes 51.1 1.64 1050 7.o No 88.5 1.86 1035 10.4 Yes 28.5 1062 1053 9.2 The electrical properties were recorded as the average for 30 cells. The superior performance and properties of the cells having the silver layer on the depolarizer blend is clearly demonstratedO
Example 3 Primary alkaline button cells (RW 44 size) were treated with 2 difPerent strong reducing agents to form a silver layer on the depolarizer blend~ and voltage and cell stability were determinedO The depolarizer blend comprised 50~ by weight AgO mix, 49% by weight Ag20 and 1% by weight polytetra-fluoroethylene. The AgO mix had the following composition:
Ingredient mount (~0 by wto) AgO 9502 Ag powder 3.0 Polytetrafluoroethylene 105 - (Teflon) Au (OH)2 0.3 All of the depolarizer blends were soaked for 1 minute in a 90/10 solution of 30% KOH/methanol, followed by rinsing and drying prior to the strong reducing agent treatment. All cells had a silver-plated sleeve around the depolarizer pellet.
Lot A was treated in a solution of 1% by weight hydrazine in _ 12 -. . .
1~42~7~
methanol for 3 minutes at room temperatureO Lot B was treated in approximately 100 ml. of 30% KOH aqueous solution to which 2mlO of 37% by weight formaldehyde in methanol was added. The solution containing the consolidated depolarizer blend was heated to 50C. and the treatment was carried out for 15 minutes.
Each lot comprised 40 cells with each cell having a zinc gel anode (99.8% by weight amalgamated zinc particles ~ 002% by weight guar gum) and a 40% KOH
1% ZnO aqueous electrolyte solutionO The following results were recorded:
FlashCell Expansion Lot Impedance Current-1 wk at 165F
Number OCVCCV (167 ohms) ~ s) _(amps)(mils) A 1.62v. 1-55v~ 203 oO76 2.7 B 1061v. 1.57v. 2~3 0.77 7-These results demonstrate that the formation of the silver layer on the depo-larizer blend surface can be accomplished with any strong reducing agent capa-ble of reducing AgO to Ag.
Eæample 4 Primary alkaline cells (RW 44 size~ having a construction similar to the cell illustrated in Figure 1 were tested to determine the effect of using varied proportions of divalent silver oxide (AgO) in the depolarizer blend.
All cells were made with a 40% potassium hydroxide aqueous solution containing 1% by weight zinc oxide. In addition to the silver oxides, the depolarizer blend contained about 1.5% by weight of polytetrafluoroethylene. The cells in Lots A-D were treated in a solution of 1% by weigh* hydrazine in methanol for -~`- 6 minutes at room temperature~ and Lots E-I were treated in the hydrazine solu-tion for 3 minutesO The electrical properties are reported as the average of 12 to 40 cells, with CCV measured through a 30 ohm load for Lots A-D and a 167 ohm load for Lots E-I, and the electrical data was recorded 1 day after closure for Lots A-D and 2 weeks after closure for Lots E~Io The cell expansion data was the average of 4 to 6 cellsO The following results were recorded:
~ ~ 4 Z 9 Flash Cell Expansion Lot Impedance OCV CCV Current 1 wk at 160F~
Number ~ ~ A~O (ohms~ _ (volts~ (30 ohms) (amps)(milsl____ A 1088.5 2.7 1-59 1.43 0.53 B 2078.5 2.5 1-59 1.44 0057 C 3068.5 2.6 1.60 1-44 o.67 o D 4 5805 2.4 1060 1.45 0.72 0 CW
(167 ohms) E 5 4805 15.7 1.60 1.48 0.49 4 F 6038.5 7703 1.58 1049 oO58 7 G 7028.5 26.0 1.75 1047 0.53 8 H 8018.5 30.0 1.83 1046 0.55 12 I 9 8.5 26.5 1085 1.38 0.44 9 These results indicate that open circuit voltage and gassing stability (cell expansion) were no problem until the depolarizer blend contained at least about 50% AgO, and the cells with depolari3er blends containing at least about 80% AgO had open circuit voltages which were too high and had increased cell expansionO
The negative electrode may be zinc, cadmium, indium, magnesium, aluminum, titani~ or manganese. It is preferred to use zinc active material which may be in the form of finely divided zinc particles, gelled or semi-gelled zinc particles, or a zinc foil. It is generally preferred that the zinc active material should be amalgamated regardless of the form which is usedO
Between the depolarizer blend and the negative electrode, there is placed a separator which generally comprises both an absorbent component and a barrier material. The absorbent component may be made from a cellulosic mate-rial such as matted cotton fibers or from a non-cellulosic material such as l~Z97~
microporous polyethylene. The absorbent material holds the electrolyte (gene-rally in contact with the negative active material), and a plurality of layers may be used. The barrier material may also comprise one or more layers for preventing the passage of metallic ions or dendrite growth from one electrode to the other. The barrier material may be any suitable semi-permeable material such as the regenerated cellulose material commercially available under the trademark "Cellophane", either alone or in combination with a synthetic bar-rier such as polyethylene grafted with methacrylic acid. It is preferred to use a laminated barrier material which comprises a layer of polyethylene grafted with methacrylic acid be~ween layers of Cellophane, ~trademark).
The cells of this invention utilize an alkaline electrolyte consis-ting essentially of an aqueous solution of potassium hydroxide. The electrolyte is preferably limited to an amount sufficient only to provide wetting of the cell components without establishing a liquid level of free electrolyte in the cell. The alkaline electrolyte preferably has a potassium hydroxide con-centration of at least about 3% by weight ranging up to about 50% by weight.
It may contain minor amounts of additives such as zinc oxide to inhibit dis-solution of the zinc negative active material, and other alkali metal hydro-xides, e.g. cesium, rubidium or sodium, may be substituted for minor portions of the potassium hydroxide.
A critical feature of this invention is the formation of the layer of silver on the surface of the depolarizer blend adjacent to the separator.
A substantially continuous and electrolyte permeable layer of silver may be fo~med by treating the surface of the depolarizer blend with a strong reducing agent such as hydrazine or formaldehyde solutions. Other relatively strong reducing agents such as hydrogen, metals ~zinc and iron), tin chloride, iron sulfate, sulfurous acid, oxalic acid, formic acid and hydroxylamine can also be used, provided that they are strong enough to reduce the depolarizer blend to silver within a reasonable time. When using hydrazine or formaldehyde, methanol solutions of the reducing agent are preferred and the surface of the -97g depolarizer blend is treated for several minutes, generally from about 2-6 minutes is su-fficient. A high proportions o-f AgO may require a longer reducingagent treatment. The treatment with the reducing agent is usually performed at room temperature, however~ elevated temperatures may be used especially if it is desired to accelerate the reduction. Aqueous solutions of the reducing agent can be used as well as an organic so]vent solution.
The depolarizer blend can be physically mixed, incorporating additi-ves for special purposes, and then compressed into a pellet. The entire surface of the pellet can be reduced to silver by soaking the pellet or tumblingit in the reducing agent solution. This is not a preferred method, for it was found that pieces of the compressed depolarizer pellet broke off during the reduction treatment, and in some cases there was non-uniform pellet reduction~
In addition to physical mixing, the depolarizer blend may be prepared by (1) oxidizing silver powder, ~2) reducing a portion of a divalent silver oxide active material, or (3) reducing the AgO in situ by mixing it with a reducing metal such as zinc or cadmium.
The preferred method for manufacturing the depolarizer blend com-prises (1) forming the depolarizer blend comprising divalent silver oxide and monovalent silver oxide9 (2) compressing the blend in a press to form a pellet using a pressure ranging from about 40,000 to 60,000 psi, (3) placing the pellet in the cathode container, (4) consolidating the pellet in the con-tainer by compression using a consolidation pressure ranging from about 50,000 to 70,000 psi, and (5) treating the consolidated pellet/cathode container component with the reducing agent solution. In this preferred method, the bottom and sides of the depolarizer blend pellet remain non-reduced, however, treatment with the reducing agent may be carried out prior to consolidation~
It is preferred to place a sleeve around the upper edge of the depolarizer blend, and this may be done prior to consolidating the pellet in the cathode containerO The sleeve functions as a supporting surface to protect ~he 1~)429~9 depolari~er pellet during consolidation and when the cell is sealed by crimping the upper edge of the cathode container upon the grommet molded on the edge of the anode container.
One of the principal objectives of this invention is to increase the energy density per unit weight or volume of the depolarizerO Maximum energy density would be achieved by using only divalent silver oxide depolarizer materialg but the resultant cell has two vol~age plateaus during discharge and the divalent silver oxide is very unstable in the potassium hydroxide electrolyte. It has been found that the depolarizer blend can contain a maxi-mum of about 70% by weight of divalent silver oxide and still provide a highdrain rate alkaline cell having a single voltage plateau and a stable depola-rizer. When mass producing the high drain rate, primary alkaline cells, it is generally preferred to use a depolarizer blend comprising at least about 50%
divalent silver oxide in order to insure that the cell has a single voltage plateau, satisfactory elevated temperature stability, and improved electro-chemical capacity.
; Referring now to Figure 1~ a button cell construction (10) is illus-trated~ for the high drain rate, primary alkaline cells of this invention are particularly adapted for use in this construction, and button cells were used to evaluate the divalent silver oxide/monovalent silver oxide depolari~er blendsO These button cells are of the type currently used as a power source for electronic watches, an application for which the high drain rate, primary alkaline cells having a divalent silver oxide/monovalent silver oxide depola-rizer blend coated with a layer of silver are particularly effective.
The negative electrode (anode) container (11) comprises what is commonly referred to as a "double top". Two cans are placed in physical, electrical contact with each other, with the inner can (12) being nested in the outer can (13) to form a tight friction fit. It is generally preferred to spot weld the cans together as indicated at (14) to maintain permanent ~)42~9 electrical contactc The cans may be made from nickel-plated stcel which has good corrosion resistance, however, other materials may be used and the sur-faces of the cans can be given special coatings. The "double top" anode con-tainer is pref7erred for its superior leakage prevention properties~ however~
a single top container can be used. A collar orgrommet (15) of nylon or poly-ethylene is molded onto the edge of the anode container (11) to electrically insula~e it from the depolarizer (cathode) container (16)o. The negatiue elec-trode or anode ¦17) is a zinc active material in the form of a gel or semi-gel comprising finel~ divided zinc particles, a small amount of gelling agent such as guar gum or carboxymethyl cellulose (e.gO 0.2% by weight) and a portion of the aqueous potassium hydroxide electrolyte solution.
The separator comprises an abs~rbent component (18) and a barrier material (19). It is preferred to use matted cotton fibers (commercially available under the trademark "~ebril") as the absorbent component which also contains a portion of the alkaline electrolyteO The semi-permeable barrier material comprises a layer (20) of polyethylene grafted with methacrylic acid (commercially available under the trademark "Permion") sandwiched between layers A ~ ~ ~ I/dp~
(21) of ~e~10~h~n~. The absorbent component (18) is placed in contact with the ~inc active material, and the barrier material is in contact with the silver layer (22) on the surface of the depolarizer blend (23)o The depolarizer blend or cathode (23) comprises a mixture of diva-lent silver oxide ~AgO) and monovalent silver oxide (Ag20) and additives for special effects. The depolarizer blend generally contains polytetrafluoroethy-lene as a binder and lubricant. The blend may also contain a minor amount of a gas suppressan~ such as gold hydroxide to insure the stability of the diva-lent silver oxideO The following is a preferred depolarizer blend composition:
Ingredient Amount (% by wto) Divalent Silver Oxide (AgO) 50 Monovalent Silver Oxide (Ag20) ~8.35 Polytetrafluoroethylene~ Teflon) 1.5 Gold Hydroxide - 0.15 ~q ~ e nn~ ~5 ~ 9 ~
~)4~79 The silver layer (22) is formed in situ on the depolarizer blend after it is consolidated in the cathode container (16) by immersing it in a 3% by weight hydrazine solution in methanol for about S minutes. ~hen formed in this manner~
the silver layer is substantially con~inuous and electrolyte permeableO A
sleeve (241 is placed around the upper edge of the depolarizer blend, however, this is not an essential component of the button cell constructionO If desired, the entire surface of the depolarizer blend (23) can be reduced by carrying out the reduction treatment prior to consolidation in container (16)o The high drain rate~ primary alkaline cells of this invention are specially designed and constructed as power sources for electronic watches having a light emitting diode ~IED) display. These watches require a battery which is capable of providing a high drain rate discharge in the form of pulsesO
It is essential in order to light the display for a reasonable number of p~ses that the primary alkaline cells be capable of providing a flash current greater than an average of 0.2 amperes per square centimeter of cell cross-sectional areaO In addition, the cell system must have improved stability in the pre-sence of alkaline electrolyte~ for the potassium hydroxide electrolyte requ1-red for the high drain rate capability accentuates the propensity of the divalent silver oxide to evolve gas in the presence of alkaline solutions. In some cases it may be necessary to precondition the cell before using it as a power source by short circuiting the cell for a few seconds. It has been dis-covered that this preconditioning increases the flash current of the cell and provides more uniform flash current performance.
Example 1 Primary alkaline button cells (RW 44 size having a cathode container diameter of 0.450 inches and a height ranging from about 00150 to about 0.162 inches) having the construction illustrated in Figure 1 were tested to deter-mine the effect of a silver layer placed on the depolarizer blend surface for high rate cells (35% KOH t 1% ZnO aqueous electrolyte solution)O In ~6~4~
addition to the mixture of divalent and monovalent silver oxides~ the depola-rizer blend contained 1.5% by weight of polytetrafluoroethylene and 0.15% by weight of gold hydroxide. The depolarizer blend was immersed, after consolida-tion in the cathode container, in a 3% by weight hydrazine in methanol solution for 3 minutes to f~rm the substantially continuous silver layer. The anode was a zinc blend comprising 99.8% by weight of amalgamated zinc particles (7%
mercury) and 002% by weight of guar gum gelling agent. The closed circuit voltage (CCV) was measured through a 167 ohm loadO The electrical properties and stability were recorded as the average for 30 cellsO The flash current was measured by electrically connecting a cell to a standard ammeter (having an internal resistance of about 0.015 ohms~ and determining the current flow at 0.5 secondsO The following results were recorded:
Cell Electrical Properties Expansion Flash 4 wks. at % AgO in Electro- Silver Impedance OCV CCV Current 165 F
Depolarizer lyte Layer (ohms) (volts) (volts) (amps) (mils) 40 ~OH No34.4 1085 1.28 0015 2102 40 " Yes3.4 1.60 1-55 0.69 12.5 30 " No35.7 1.85 1.15 0013 2007 30 " ~es3.0 1060 1-55 0.71 806 The superior performance and properties of the cells having a silver layer on the depolarizer blend is clearly demonstrated.
Example 2 Primary alkaline button cells (RW 44 size) having the construction illustrated in Figure 1 were made to determine the effect of varying the AgO/
Ag20 ratio in combination with and without a hydrazine reduction treatment to form a silver layer on the depolarizer blendO The hydrazine treatment consis_ ted of soaking the consolidated pellets in a sclution of 1% by weight hydra-zine in methanol, with stirring, for 3 minutes. In each of the cells, the sleeve around the depolarizer pellet was silver-platedO The electrolyte was a _ 11 --97~
40% KOH ~ 1% ~nO aqueous solution~ The following results were recorded:
Cell Electrical Properties Expansion 7 days % AgO in Silver Impedance OCV CCV(1670hms) at 165 F
Depolari7er Layer (ohms~ ~ (voltsl (mils) No 98-4 1.86 1.33 804 Yes 2.9 1.61 1.55 4.4 No 97-4 1.86 1.34 7-0 Yes 2.7 1.61 1-55 6.2 No 93.6 1.86 1.37 15.4 Yes 9.9 1.61 1.54 16.4 No 99.4 1.86 1.34 7~4 Yes 51.1 1.64 1050 7.o No 88.5 1.86 1035 10.4 Yes 28.5 1062 1053 9.2 The electrical properties were recorded as the average for 30 cells. The superior performance and properties of the cells having the silver layer on the depolarizer blend is clearly demonstratedO
Example 3 Primary alkaline button cells (RW 44 size) were treated with 2 difPerent strong reducing agents to form a silver layer on the depolarizer blend~ and voltage and cell stability were determinedO The depolarizer blend comprised 50~ by weight AgO mix, 49% by weight Ag20 and 1% by weight polytetra-fluoroethylene. The AgO mix had the following composition:
Ingredient mount (~0 by wto) AgO 9502 Ag powder 3.0 Polytetrafluoroethylene 105 - (Teflon) Au (OH)2 0.3 All of the depolarizer blends were soaked for 1 minute in a 90/10 solution of 30% KOH/methanol, followed by rinsing and drying prior to the strong reducing agent treatment. All cells had a silver-plated sleeve around the depolarizer pellet.
Lot A was treated in a solution of 1% by weight hydrazine in _ 12 -. . .
1~42~7~
methanol for 3 minutes at room temperatureO Lot B was treated in approximately 100 ml. of 30% KOH aqueous solution to which 2mlO of 37% by weight formaldehyde in methanol was added. The solution containing the consolidated depolarizer blend was heated to 50C. and the treatment was carried out for 15 minutes.
Each lot comprised 40 cells with each cell having a zinc gel anode (99.8% by weight amalgamated zinc particles ~ 002% by weight guar gum) and a 40% KOH
1% ZnO aqueous electrolyte solutionO The following results were recorded:
FlashCell Expansion Lot Impedance Current-1 wk at 165F
Number OCVCCV (167 ohms) ~ s) _(amps)(mils) A 1.62v. 1-55v~ 203 oO76 2.7 B 1061v. 1.57v. 2~3 0.77 7-These results demonstrate that the formation of the silver layer on the depo-larizer blend surface can be accomplished with any strong reducing agent capa-ble of reducing AgO to Ag.
Eæample 4 Primary alkaline cells (RW 44 size~ having a construction similar to the cell illustrated in Figure 1 were tested to determine the effect of using varied proportions of divalent silver oxide (AgO) in the depolarizer blend.
All cells were made with a 40% potassium hydroxide aqueous solution containing 1% by weight zinc oxide. In addition to the silver oxides, the depolarizer blend contained about 1.5% by weight of polytetrafluoroethylene. The cells in Lots A-D were treated in a solution of 1% by weigh* hydrazine in methanol for -~`- 6 minutes at room temperature~ and Lots E-I were treated in the hydrazine solu-tion for 3 minutesO The electrical properties are reported as the average of 12 to 40 cells, with CCV measured through a 30 ohm load for Lots A-D and a 167 ohm load for Lots E-I, and the electrical data was recorded 1 day after closure for Lots A-D and 2 weeks after closure for Lots E~Io The cell expansion data was the average of 4 to 6 cellsO The following results were recorded:
~ ~ 4 Z 9 Flash Cell Expansion Lot Impedance OCV CCV Current 1 wk at 160F~
Number ~ ~ A~O (ohms~ _ (volts~ (30 ohms) (amps)(milsl____ A 1088.5 2.7 1-59 1.43 0.53 B 2078.5 2.5 1-59 1.44 0057 C 3068.5 2.6 1.60 1-44 o.67 o D 4 5805 2.4 1060 1.45 0.72 0 CW
(167 ohms) E 5 4805 15.7 1.60 1.48 0.49 4 F 6038.5 7703 1.58 1049 oO58 7 G 7028.5 26.0 1.75 1047 0.53 8 H 8018.5 30.0 1.83 1046 0.55 12 I 9 8.5 26.5 1085 1.38 0.44 9 These results indicate that open circuit voltage and gassing stability (cell expansion) were no problem until the depolarizer blend contained at least about 50% AgO, and the cells with depolari3er blends containing at least about 80% AgO had open circuit voltages which were too high and had increased cell expansionO
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A high drain rate, primary alkaline cell comprising a negative electrode, a divalent silver oxide/monovalent silver oxide depolarizer blend, a separator between said negative electrode and the depolarizer blend, and an aqueous potassium hydroxide electrolyte, said depolarizer blend containing up to about 70% by weight of divalent silver oxide, and a substantially continuous and electrolyte permeable layer of silver on the surface of the depolarizer blend adjacent to the separator, whereby the cell is characterized by the stability of the depolarizer blend in the potassium hydroxide electrolyte, a maximum open circuit voltage of about 1.75 volts, a single voltage plateau during discharge and is capable of providing a flash current greater than an average of 0.2 amps per square centimeter of cell cross-sectional area.
2. A primary alkaline cell in accordance with claim 1 in which only the surface of the depolarizer blend adjacent to the separator is coated with a substantially continuous and electrolyte permeable layer of silver.
3. A primary alkaline cell in accordance with claim 1 in which the concentration of the aqueous potassium hydroxide electrolyte ranges from at least about 3% by weight up to about 50% by weight of potassium hydroxide.
4. A method for manufacturing the depolarizer blend used in the pri-mary alkaline cell of claim 1 which comprises (1) forming the depolarizer blend comprising divalent silver oxide and monovalent silver oxide, (2) com-pressing the blend to form a pellet, (3) placing the pellet in a cathode container, (4) consolidating the pellet in the container by compression, and (5) treating the consolidated pellet/cathode container component with a strong reducing agent for a period of time sufficient to reduce the surface of the depolarizer blend to metallic silver.
5. The method of claim 4 in which the strong reducing agent comprises hydrazine.
6. The method of claim 5 in which the hydrazine is present in a metha-nol solution in an amount ranging from about 1 to about 5% by weight, and the treatment of the consolidated pellet/cathode container with the hydrazine in methanol solution has a duration of from about 2 minutes to about 6 minutes.
7. The method of claim 4 in which the depolarizer blend ingredients which are mixed in step (1) include a minor amount of polytetrafluoroethylene.
8. The method of claim 4 in which a sleeve is placed around the upper edge of the depolarizer blend prior to consolidating the pellet in step (4).
9. A method for manufacturing the depolarizer blend used in the primary alkaline cell of claim 1 which comprises (1) forming the depolarizer blend comprising divalent silver oxide and monovalent silver oxide, (2) compressing the blend to form a pellet, (3) treating the pellet with a strong reducing agent for a period of time sufficient to reduce the surface of the depolarizer blend to metallic silver, (4) placing the pellet with the reduced surface in a cathode container, and (5) consolidating the pellet with the reduced surface in the cathode container by compression.
10. The method of claim 9 in which the strong reducing agent comprises hydrazine.
11. A method for manufacturing the depolarizer blend used in the primary alkaline cell of Claim 1 which comprises the steps of: (1) forming the depolarizer blend which comprises divalent silver oxide and monovalent silver oxide (2) compressing the blend to form a pellet, (3) placing the pellet in a cathode container, (4) consolidating the pellet in the cathode container by compression, wherein the pellet is treated, subsequent to the step of compressing the blend to form the pellet, with a strong reducing agent for a period of time sufficient to reduce the surface of the depolarizer blend to metallic silver.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US66665776A | 1976-03-15 | 1976-03-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1042979A true CA1042979A (en) | 1978-11-21 |
Family
ID=24674914
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA265,958A Expired CA1042979A (en) | 1976-03-15 | 1976-11-17 | High drain rate, primary alkaline cell having a divalent silver oxide/monovalent silver oxide depolarizer blend coated with a layer of silver |
Country Status (16)
| Country | Link |
|---|---|
| AU (1) | AU498599B2 (en) |
| BE (1) | BE848492A (en) |
| CA (1) | CA1042979A (en) |
| CH (1) | CH617292A5 (en) |
| DE (1) | DE2652561A1 (en) |
| DK (1) | DK516676A (en) |
| ES (1) | ES453453A1 (en) |
| FR (1) | FR2344970A1 (en) |
| GB (1) | GB1505799A (en) |
| IN (1) | IN145524B (en) |
| IT (1) | IT1066725B (en) |
| MX (1) | MX144079A (en) |
| NL (1) | NL7612759A (en) |
| NO (1) | NO763885L (en) |
| SE (1) | SE439860B (en) |
| ZA (1) | ZA766559B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4009056A (en) * | 1976-03-15 | 1977-02-22 | Esb Incorporated | Primary alkaline cell having a stable divalent silver oxide depolarizer mix |
| US4015056A (en) * | 1976-03-15 | 1977-03-29 | Esb Incorporated | Method of manufacturing a stable divalent silver oxide depolarizer mix |
| DE2757583C2 (en) * | 1977-12-23 | 1984-10-25 | Varta Batterie Ag, 3000 Hannover | Galvanic cell with alkaline electrolyte and process for its manufacture |
| CH639512A5 (en) * | 1978-07-06 | 1983-11-15 | Leclanche Sa | LOW-WATER ALKALINE PRIMARY CELL WITH LONG LIFE. |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3907598A (en) * | 1973-04-26 | 1975-09-23 | Esb Inc | Sealed low drain rate dry cell having in situ stable divalent silver oxide depolarizer |
| JPS50160733A (en) * | 1974-06-17 | 1975-12-26 | ||
| US3920478A (en) * | 1974-06-25 | 1975-11-18 | Union Carbide Corp | Divalent silver oxide-zinc cell having a unipotential discharge level |
-
1976
- 1976-11-02 ZA ZA766559A patent/ZA766559B/en unknown
- 1976-11-04 MX MX166886A patent/MX144079A/en unknown
- 1976-11-15 SE SE7612708A patent/SE439860B/en unknown
- 1976-11-15 NO NO763885A patent/NO763885L/en unknown
- 1976-11-15 IN IN2047/CAL/76A patent/IN145524B/en unknown
- 1976-11-15 IT IT52194/76A patent/IT1066725B/en active
- 1976-11-15 GB GB47510/76A patent/GB1505799A/en not_active Expired
- 1976-11-17 DK DK516676A patent/DK516676A/en not_active Application Discontinuation
- 1976-11-17 CA CA265,958A patent/CA1042979A/en not_active Expired
- 1976-11-17 NL NL7612759A patent/NL7612759A/en not_active Application Discontinuation
- 1976-11-18 ES ES453453A patent/ES453453A1/en not_active Expired
- 1976-11-18 DE DE19762652561 patent/DE2652561A1/en not_active Withdrawn
- 1976-11-18 BE BE172482A patent/BE848492A/en unknown
- 1976-11-18 FR FR7634747A patent/FR2344970A1/en active Granted
- 1976-11-18 AU AU19781/76A patent/AU498599B2/en not_active Expired
- 1976-11-18 CH CH1453476A patent/CH617292A5/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| FR2344970A1 (en) | 1977-10-14 |
| AU498599B2 (en) | 1979-03-15 |
| CH617292A5 (en) | 1980-05-14 |
| BE848492A (en) | 1977-03-16 |
| DK516676A (en) | 1977-09-16 |
| DE2652561A1 (en) | 1977-09-22 |
| ES453453A1 (en) | 1977-11-16 |
| NO763885L (en) | 1977-09-16 |
| AU1978176A (en) | 1978-05-25 |
| SE439860B (en) | 1985-07-01 |
| FR2344970B1 (en) | 1981-02-06 |
| NL7612759A (en) | 1977-09-19 |
| ZA766559B (en) | 1977-12-28 |
| GB1505799A (en) | 1978-03-30 |
| IN145524B (en) | 1978-11-04 |
| SE7612708L (en) | 1977-09-16 |
| IT1066725B (en) | 1985-03-12 |
| MX144079A (en) | 1981-08-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4048405A (en) | High drain rate, primary alkaline cell having a divalent silver oxide/monovalent silver oxide depolarizer blend coated with a layer of silver | |
| AU682541B2 (en) | Sealed rechargeable cells containing mercury-free zinc anodes, and a method of manufacture | |
| US4009056A (en) | Primary alkaline cell having a stable divalent silver oxide depolarizer mix | |
| US7169508B2 (en) | Method of manufacturing anode compositions for use in rechargeable electrochemical cells | |
| US3880672A (en) | Battery barrier and battery | |
| US4327157A (en) | Stabilized nickel-zinc battery | |
| US8048556B2 (en) | Battery separator | |
| KR20120023806A (en) | Pasted zinc electrode for rechargeable zinc batteries | |
| EP0845827A2 (en) | Substantially mercury-free electrochemical cells | |
| KR20120027273A (en) | Nickel hydroxide electrode for rechargeable batteries | |
| CA1090415A (en) | Additive for an alkaline battery employing divalent silver oxide positive active material | |
| CA1072178A (en) | Method of manufacturing a stable divalent silver oxide depolarizer mix | |
| US4397925A (en) | Alkaline battery with reducing agents in the electrolyte | |
| CZ294824B6 (en) | Alkaline galvanic cell and process for producing thereof | |
| US4167609A (en) | Zinc oxide additive for divalent silver oxide electrodes | |
| US4056664A (en) | Electrochemical cell having an AgO electrode discharging at an Ag2 O voltage level | |
| JP5361859B2 (en) | Multilayer cathode structure with silver-containing layer for small cells | |
| CA1042979A (en) | High drain rate, primary alkaline cell having a divalent silver oxide/monovalent silver oxide depolarizer blend coated with a layer of silver | |
| US4250234A (en) | Divalent silver oxide cell | |
| KR100773952B1 (en) | Anode active material for mercury-free air zinc cell and mercury-free air zinc cell comprising the same | |
| KR810000418Y1 (en) | High drain rate, primary alkaline cell having a divalent silver oxide/monovalent silver oxide depolarizer blend coated with a layer of silver | |
| KR810000419Y1 (en) | Primary alkaline cell having a stable divalent silver oxide depolarizer mix | |
| JPS59186255A (en) | Alkali primary battery | |
| CA2455548A1 (en) | Alkaline manganese dioxide cell with improved open circuit voltage |