CA2032530C - Air assisted alkaline cells - Google Patents
Air assisted alkaline cells Download PDFInfo
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- CA2032530C CA2032530C CA002032530A CA2032530A CA2032530C CA 2032530 C CA2032530 C CA 2032530C CA 002032530 A CA002032530 A CA 002032530A CA 2032530 A CA2032530 A CA 2032530A CA 2032530 C CA2032530 C CA 2032530C
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- 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
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- 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
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/40—Alloys based on alkali metals
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M12/00—Hybrid cells; Manufacture thereof
- H01M12/04—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type
- H01M12/06—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type with one metallic and one gaseous electrode
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- 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
- H01M4/64—Carriers or collectors
- H01M4/70—Carriers or collectors characterised by shape or form
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- 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
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/10—Primary casings; Jackets or wrappings
- H01M50/147—Lids or covers
- H01M50/148—Lids or covers characterised by their shape
- H01M50/1535—Lids or covers characterised by their shape adapted for specific cells, e.g. electrochemical cells operating at high temperature
- H01M50/1537—Lids or covers characterised by their shape adapted for specific cells, e.g. electrochemical cells operating at high temperature for hybrid cells
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/10—Primary casings; Jackets or wrappings
- H01M50/147—Lids or covers
- H01M50/148—Lids or covers characterised by their shape
- H01M50/154—Lid or cover comprising an axial bore for receiving a central current collector
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Hybrid Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Inert Electrodes (AREA)
Abstract
An air assisted alkaline cell having a cathode made from a mixture of porous manganese dioxide and substantially less porous manganese dioxide. The substantially solid MnO2 is the major component of the cathode with the porous MnO2 being present in an amount effective to enable recharging of the cathode of the air assisted alkaline cell in the presence of air. The composi-tion of the cathode is disclosed as well as the method of making the cathode. An improved air assisted alkaline cell is also disclosed, as well as the method for making the improved air assisted cell.
Description
AIR ASSISTED ALTCALINE CELLS
BACKGROUND OF THE INVENTION
The present invention relates to air assisted alkaline cells.
Alkaline cells axe well known in the art. A
conventional alkaline cell employs a zinc anode, manganese dioxide as the cathode with an aqueous solution of potassium hydroxide for the electrolyte. These cells are readily available commercially for industrial and home applications.
Recently a new type of alkaline cell was disclosed by Cegasa International, a Spanish company. It is an air assisted cell employing zinc as the anode and manganese dioxide as the cathode with an aqueous solution of potassium hydroxide as the electrolyte. The cell is designed so that Z5 the positive electrode containing the manganese dioxide (Mn02) is sups>orted about its periphery and along its full length in the cell by a perforated ribbed air distribution grid. The botaom or negative end of the cell has an insu-lating support which allows air to enter the cell and pass up along the outside of the supported positive electrode.
When the cell is initially put into a circuit, the electro-chemical reaction depends primarily upon the presence of the manganese dioxide cathode. As the reaction progresses, and the manganese dioxide cathode is electrochemically reduced, air within the cell reoxidizes and recharges the manganese dioxide.
While the Cegasa cell does function for its intended purpose, it is a complex cell in that it requires a cathode support completely surrounding the cathode for exposing the surface of the cathode to air. Also, the interior of the cell has a complex pattern of supports and air distribution passages to allow air to enter the cell and contact the MnOz.
As mentioned previously, the Cegasa air assisted alkaline cell employs manganese dioxide as the active cathode material. There is no teaching in any of the Cegasa literature presently known to the inventor that the manganese dioxide used is anything other than conventional electrolytically deposited manganese dioxide which is typically used in alkaline cells.
The Cegasa literature shows no awareness of any improvement to be gained through the use of mixtures of different types of manganese dioxide.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved air assisted alkaline cell has been prepared which does not require the presence of an air distribution grid which is expensive and which occupies space within the cell that otherwise could be occupied by active material to increase the energy capacity of the cell. The improved cell therefore has increased continuous drain service in an air free environment because of an increase in amount of MnOz in the cell. Likewise, it has improved energy capacity in the presence of air due to an increased amount of zinc in the cell. The improved air assisted alkaline cell employs a mixture of highly porous manganese dioxide and substantially solid manganese dioxide.
The invention provides a cathode for an air assisted alkaline cell comprising a mixture of porous MnOz and substantially solid Mn02 with the porous MnOz being present in an effective amount to provide air paths into the cathode and thereby recharge the cell in the presence of air.
Still further, the invention provides a cathode for an air assisted alkaline cell comprising a mixture of a porous MnOz and a substantially solid Mn02 having a packing density gradient when shaped into a cathode with the lowest packing density predominating at the portion of the cathode intended to be contacted by air during the operation of the cell.
In another embodiment, the invention provides a composition suitable for use in the manufacture of a cathode for an air assisted alkaline cell comprising a mixture of highly porous Mn02 and substantially solid Mn02 with the highly porous MnOz being present in an amount effective to enable recharging of the cathode prepared from the mixture when used in an air assisted alkaline cell in the presence of air and with the substantially solid MnOz being present in an amount to produce an acceptable alkaline cell in the absence of air.
The invention also includes a cathode prepared from the mixture, as well as the method of preparing the cathode, an air assisted alkaline cell incorporating the cathode and the method of manufacturing the air assisted alkaline cell. More particularly and in line with the above, the invention comprehends a method for preparing aTcathode for use in an air assisted alkaline cell comprising the following steps, mixing a composition comprising porous Mn02 and substantially solid MnOz with the porous MnOz being present in an amount effective to recharge the cathode in the presence of air, forcing the composition into a form, subjecting the composition to pressure while in the form to shape a cathode having a packing gradient with the lowest volume percent of solids being at one end of the cathode and the highest at the other end of the cathode.
Further, the invention provides an air assisted alkaline cell comprising a conductive container for supporting the components of the cell and for forming an external terminal for the cell, a cathode electrode in contact with the inner wall of the container, the cathode comprising a mixture of porous Mn02 and substantially solid Mn02 with the porous Mn02 being present in an effective amount to recharge the cell in the presence of air. An anode electrode comprises metallic zinc, a binder, an electrolyte and a separator electrically isolates the cathode electrode from the anode electrode. An anode current collector is in electrical contact with the anode electrode and an external terminal for the cell is a.n contact with the anode current collector. An aqueous alkaline electrolyte is provided for facilitating the electrochemical reaction a.n the cell and an air permeable seal closes the conductive container and allows oxygen to enter the cell and come in contact with the cathode electrode.
Still further, the invention provides a method for preparing an air assisted alkaline cell comprising the following steps, providing a conductive container for the cell which can serve as the first external terminal for the cell, providing a conductive container for the cell which can serve as the first external terminal for the cell, preparing a mixture of porous Mn02 and substantially solid Mn02, loading the mixture of porous Mn02 and substantially solid MnOz into the container to form a cathode electrode, adding a separator to the container to electrically isolate the cathode electrode from the anode electrode, adding a zinc anode composition to the container in contact with the separator and providing an anode current collector and an air permeable conductive cover for the cell, the conductive cover forming the second external terminal for the cell.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a sectional view of an inverted air assisted alkaline cell of the present invention.
Fig. 2 is an exploded view of the subassembly used in assembling the cell.
Fig. 2A is a plan view of the air permeable seal member used in the subassembly of Fig. 2.
Fig. 3 is a series of curves generated through the continuous discharge of several different cells.
Fig. 4 is a series of curves generated through the intermittent discharge of several different cells.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Fig. 1, the air assisted alkaline cell is assembled in a conventional conductive steel container 11 which also forms an external terminal for the cell. The cathode for the cell 13 is a mixture of highly porous manganese dioxide and substantially solid manganese dioxide. The mixture is prepared in a conventional mixer.
A good source of highly porous manganese dioxide is so-called chemically synthesized manganese dioxide or CMD. CMD
is usually marketed with a porosity of 25~ to 35%.
However, CMD can be prepared in the form of very porous spheres having a porosity of approximately 600. The porous 20~~~~~
1 spheres have a substantial amount of surface available for reaction with oxygen in an air assisted cell. If a cell were prepared using CMD as the only active cathode material the total energy capacity of the cell would be lowered due to the decrease in the amount of Mn02 available per unit volume of cathode.
In order to increase the total energy capacity of the cell in an air free environment, substantially solid Mn02 must be available for the cell reaction. A good source of substantially solid Mn02 is electrolytically deposited Mno2 or EMD. EMD can be obtained in the form of dense particles after the electrolytically deposited material is stripped from the electrodes, crushed and screened. EMD has a porosity of approximately 10%-16% and therefore is a sub-stantially solid material.
Since CMD and EMD are both porous materials with CMD being substantially porous while EMD is substantially solid, the terms CMD or highly porous and EMD or sub-stantially solid will be used to characterize the materials in this specification.
The use of CMD and EMD in the manufacture of cathodes far dry cells has been known for many years. CMD
and EMD have each been mixed with naturally occurring manganese dioxide to forir~ cathodes. To date, the inventor is aware of no one mixing CMD arid EMD for use in the cathode of an air assisted alkaline cell and of the inventive results obtained through the use of a mixture of these materials.
Since in the operation of an air assisted cell the Mn02 is regenerated, only sufficient highly porous MnO~ is necessary to provide good rechargeability of the Mn02 in the ~fl~~5~~
1 presence of air. Tn order to increase the total energy capacity of the cell, EMD can be added to supply additional active cathode material. As the ratio of EMD to CMD
increases, the cel l s air free capacity also increases. The amount of CMD and EMD used in the cathode of the cell depends on the desired parameters of the cell with, for example, more or less CMD being used per cathode depending on the energy capacity desired in the presence of air. For a good sell capacity in an air free environment and good rechargeability in an environment containing air, a mixture of 1:5, that is, one part by weight of CMD to five parts by weight of EMD is preferred.
While CMD is a good source of highly porous manganese dioxide, other sources are available now anra will be available in the future; therefore, the present invention is not so limited. Likewise, EMD is a readily available source of bulk, substantially solid, manganese dioxide, however, other sources are available including naturally occurring manganese dioxide, and even conventionally available low porosity CMD, and, therefore, the present invention is not limited to EMD.
The CMD and EMD are added to the mixer along with a small amount of Teflon, approximately 0.6% by weight of an aqueous solution, which is used to selectively wetproof the 2~ cathode and to improve the stability of the formed electrode structure. Teflon is a trademark of DuPont and is used to identify polytetrafluoroethylene polymeric materials. The selective wetproofing of the Mn02 keeps some of the CMD
surface available for contact with air so that the Mn02-air-electrolyte junction needed for rechargeability is achieved in the finished cell. After thoroughly mixing the 1 components, the cathode composition is poured into a steel container for the cell. An impact extruder is used to load the cell container with the cathode material. Under the pressure of the impact extruder, the cathode material becomes tightly packed about the walls of the container, with the Teflon serving to bind the mixture into a compact mass. Tt has been observed in the manufacture of the cells that a porosity gradient is formed in the manganese dioxide in the cathode, with the highest packing density being at the bottom of the container and with the lowest packing density at the top. The top of the cathode is not as tightly packed as the bottom and, in turn, more of the CMD/EMD mixture is exposed to air access at the top. The packing density of the material at the top of the formed cathode is approximately 70% while the packing density at the bottom is approximately 100%.
It is very important in the operatian of the cathode for t:he air assisted alkaline cell of the present invention th~~t some of the Mn02 be exposed simultaneously to a conductor, to electrolyte and to air. In the Cegasa cell this was achieved through the use of the air distribution grid. No such grid is used or required in the inventive cell with the highly porous Mn02 providing a surface area of Mn02 and air paths into the top of the cathode for the re-charging of the air assisted cell while the substantially solid Mn02 provides the bulk presence of manganese dioxide for the conventional operation of the alkaline cell.
CMD can be prepared starting with manganese ore which is first converted to a nitrate which is then treated with ammonium carbonate and chemical oxidants to form manganese carbonate. The manganese carbonate, after ~0~2~~~
washing, is roasted in the presence of oxygen and chemical oxidants to form manganese dioxide which is purified by washing to obtain the battery grade manganese dioxide material. The preferred CMD used in the preparation of the cathode of the air assisted cell is a material obtained from Sedema which is a division of Sadacam S.A. of Brussels, Belgium. The material is identified by Sedema as Sedema TR
manganese dioxide. The material has a porosity of approx-imately 60%. The EMD is obtained from the electrolytic deposition of manganese dioxide and is supplied by the assignee of the instant application. The EMD can also be purchased fram commercial suppliers. When the materials are combined in a homogeneous mixture, and then added to the container to form the cathode, the preferred average porosity for the cathode is 20%. CMD has a porosity of approximately .13 cc/g while EMD has a porosity of approximately .022 to 0.035 cc/g.
After the cathode is formed in the container, a separator 15 is added to electrically isolate the anode material from the cathodo and the container while still permitting ion transport between the electrodes. The anode material 17 is then added to the separator lined cavity of ...
the cell. The anode material comprises a mixture of zinc powder, a gel forming binder and the liquid electralyte used in the cell. The preferred binder is Carbopol 934 which is a carboxy polymethylene polymer available from the B. F.
Goodrich Company, of Cleveland, Ohio.
In an air assisted cell, the discharged active cathode, that is the manganese dioxide, undergoes a reaction with the air in the cell and with air which can enter the cell to become recharged, reoxidizing the reduced manganese ~0~2~~
1 oxide to manganese dioxide. In the discharge of the alkaline cell, the manganese dioxide is reduced to a lower oxidation state. The oxygen in the air will spontaneously restore or regenerate the higher oxidation state over a period of time. If the cell is subjected to brief periods of high rate discharge, then the cell must be rested for substantial periods of time between each discharge to enable the air to completely recharge the Mno2. However, if the cell is continuously discharged at a rate which is less than the rate at which the Mn02 is recharged by the incoming air, then the air recharges the Mn02 as quickly as it is dis-charged. In other words, regardless of the rate at which the cell is discharged, if the cell is drained at a low rate or is rested for a sufficient period of time, then the cathode's ability to be recharged is limited only by its access to air. The cathode material is regenerated without involving th~3 zinc anode material. Tha zinc is oxidized during the d:lscharge but it cannot be regenerated during a rest period. In view of this, less cathode material needs to be added to an air assisted alkaline cell and, in turn, the volume of zinc can be increased in the cell to increase the overall capacity of the cell.
Returning again to a discussion of Fig. 1, the alkaline electrolyte solution :Ls approximately a 34% to 37%
by weight solution of potassium hydroxide in water. The electrolyte from the anode mixture 17 permeates the separator 15, and the cathode 13. An open area 19 is left in the cell to provide room for expansion of the anode mixture 17.
A subassembly indicated generally by the number 20, referring to Fig. 2, is used to close the cell. The _g_ ~0~~~~ ~~
1 subassembly consists of an anode current collector 21, a seal member 23, an air permeable gasket 25, a neutral cover 27 and a rivet 29 which is used to join the several pieces together.
The anode current collector 21 is made from an electrically conducting metal that is inert to the cell's caustic environment. The collector metal preferably is sheet brass. The anode current collector 21 is rolled to have an arcuate shape. The sheet metal is folded over to form a flat surface which fits tightly against the bottom of the seal member 23. A nail shaped collector is also suitable.
The seal member 23 is made of an organic polymeric material which is compatible with the several components of the cell. The preferred material is polypropylene. The seal member 23 has a substantially flat bottom portion 33 surrounding a sleeve 35. Below and in line with the periphery of 'the bottom portion 33 is a substantially circular projecting first wall portion 37. A plurality of circumferentially spaced spokes 39 extend from the periphery of the bottom portion 33 out to and below a second wall portion 41 extending upwardly away from bottom portion 33.
The spaces 43 between the spokes 39 provide a passage for air to pass through the seal member 23.
A membrane 25 fits within the area of the seal member 23 bounded by the wall 41. The membrane is made of two layers of Teflon. One layer is a nonwoven film and the other is a mesh. The two layers are heat sealed together and form an air permeable membrane for the cell. The gasket 25 can be fastened to the bottom 33 and the spokes 39 by welding. A fatty polyamide adhesive such as the type _9_ 1 disclosed in Winger U.S. Patent 3,922,178 can be used to backup the weld and to prevent electrolyte creep between the polypropylene seal and the microporous gasket. Two beads of the adhesive can be used. One bead is placed around the periphery of the bottom 33 where it joins the inside of the wall 41. The second bead can be placed on the bottom 33 where it joins the outer wall of the sleeve 35.
To further ensure that the microporous gasket 25 stays in position, concentric raised ridges 40 can be formed on the bottom 33 of the seal 23. The gasket 25 will then be clamped between the ridges on the bottom 33 and the neutral cover 27.
The vented neutral cover 27 is preferably made of stainless steel and has a pair of spaced apertures 45 therein to allow the passage of air into the cell. The vented cover 27 will fit within the area of the seal member 23 bounded by the wall 41.
The rivet 29 is preferably made of brass and has a thinned portion 47 which can be easily spread to bind a?..l of the parts of the subassembly 20 together.
The dimensions of the several components of the subassembly 20 and of the overall cell can be varied to meet particular size requirements for the type of cell being assembled.
The subassembly 20 is inserted into the bottom of the inverted cell as shown in Fig. 1. The wall 37 moves the top edge of the separator 15 away from the cathode material 13. The wall 37 and separator 15 protect the anode material 17 from contact with the air entering the cell. This avoids 30 the loss of zinc due to direct reaction with oxygen. The wall portion 41 of the seal assembly 23 insulates the neutral cover 27 from electrical contact with the container 11.
To complete assembly of the cell, a bottom cover 51 is placed into the steel container 11 and is also S isolated from contact with the container by the wall portion 41 of the subassembly 20. The bottom cover 51 makes electrical contacts with the rivet 29, or other suitable electrically conductive means, enabling the bottom cover 51 to become the second external terminal for the cell. The i0 edge of the steel container 11, and of the subassembly 20, are then rolled to hold the upturned portion 53 of the bottom cover 51 locked in position on the bottom of the cell. A gap 55 surrounds the bottom cover 51, separating it from contact with the container 11. The bottom cover 53 1S preferably contains three small apertures 54, two of which are shown in Fig. 1, spaced approximately 12p' apart which provide a pasteage for air to enter into the bottom of the cell. The ai.r can pass through the subassembly 20 and ' contact the top portion of the cathode through the air ' 20 passage 43. The top cover 57 can be fastened to the container by welds 59 after the cathode is rammed into place. It can be added before or after this step as it is merely attached to the container.
Several D-size air assisted alkaline cells of the present invention were tested in 2.2 ohm continuous service tests (Fig. 3). The test results showed that the air assisted cell of the present invention (1) was better than two commercially available alkaline cells (5 and 6) and much better than a commercially available air assisted alkaline 30 cell (3) and an experimental air assisted cell (2). The cell was not as good as an experimental alkaline cell (4).
~~3~a~~
1 The latter result was a function of the amount of cathode material present in the cells with the CMD of the air assisted cell (1) providing less actual Mno2.
Since an air assisted alkaline cell recovers some of its charge while standing between high rate pulsed discharges, a dry cell industry recognized intermittent discharge test was carried out (Fig. 4). In the standard test chosen, the test curves are generated by discharging D-size cells on,a,2.2 ohm load for four minutes per hour, ld eight hours per day. The total discharge time per day was 32 minutes. However, the curve marked 1 was produced by discharging a D-size cell on a 2.2 ohm load for 4 minutes per hour, twenty-four hours a day. The total discharge time per day was 96 minutes. This test regime is identified by the assignee of the present invention by the initials CIT
and is Continuous Intermittent Teat. The impact of using the industry standard test, instead of the CIT regime, is that the cell has much mare time to recover when it is tested for 32 minutes per day instead of 96, minutes per day.
Therefore, one would expect that cell 1, manufactured without an air distribution grid, would provide more service when evaluated on the industry standard test instead of the CIT test. This difference in test schedules is probably the reason for the difference in performance between cell 1, without an air grid, and the cell 2 with an air grid.
In the assembly of the air assisted alkaline cell, the air holes 54 in the external electrode 51 are closed by a suitable seal tab such as that disclosed in U.S. Patent 4,649,090 issued March 10, 1987, to Oltman et al. The seal tab protects the interior of the cell from deleterious 1 environmental conditions and maintains the freshness of the cell.
The preferred label material and configuration for the fully assembled cell is that disclosed in.U.S. latent 4,801,514 issued January 31, 1989, to Will et al. The mufti-layer adhesive label disclosed in the patent is particularly useful far dry cell batteries.
It can be seen from the discussion above that an improved air assisted alkaline cell is provided. The air assisted cell does not require a cathode support or air distribution grid, but instead relies on the porosity of the manganese dioxide to provide paths for air to travel into the electrode and thereby enable recharging of the Mn02 to occur. The poroia air distribution support is also not necessary in this cell, enabling more active materials to be employed in the same size container.
Though the invention has been described with respect to a specific preferred embodiment thereof, many variations and modifications will become apparent to those skilled in the art. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.
BACKGROUND OF THE INVENTION
The present invention relates to air assisted alkaline cells.
Alkaline cells axe well known in the art. A
conventional alkaline cell employs a zinc anode, manganese dioxide as the cathode with an aqueous solution of potassium hydroxide for the electrolyte. These cells are readily available commercially for industrial and home applications.
Recently a new type of alkaline cell was disclosed by Cegasa International, a Spanish company. It is an air assisted cell employing zinc as the anode and manganese dioxide as the cathode with an aqueous solution of potassium hydroxide as the electrolyte. The cell is designed so that Z5 the positive electrode containing the manganese dioxide (Mn02) is sups>orted about its periphery and along its full length in the cell by a perforated ribbed air distribution grid. The botaom or negative end of the cell has an insu-lating support which allows air to enter the cell and pass up along the outside of the supported positive electrode.
When the cell is initially put into a circuit, the electro-chemical reaction depends primarily upon the presence of the manganese dioxide cathode. As the reaction progresses, and the manganese dioxide cathode is electrochemically reduced, air within the cell reoxidizes and recharges the manganese dioxide.
While the Cegasa cell does function for its intended purpose, it is a complex cell in that it requires a cathode support completely surrounding the cathode for exposing the surface of the cathode to air. Also, the interior of the cell has a complex pattern of supports and air distribution passages to allow air to enter the cell and contact the MnOz.
As mentioned previously, the Cegasa air assisted alkaline cell employs manganese dioxide as the active cathode material. There is no teaching in any of the Cegasa literature presently known to the inventor that the manganese dioxide used is anything other than conventional electrolytically deposited manganese dioxide which is typically used in alkaline cells.
The Cegasa literature shows no awareness of any improvement to be gained through the use of mixtures of different types of manganese dioxide.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved air assisted alkaline cell has been prepared which does not require the presence of an air distribution grid which is expensive and which occupies space within the cell that otherwise could be occupied by active material to increase the energy capacity of the cell. The improved cell therefore has increased continuous drain service in an air free environment because of an increase in amount of MnOz in the cell. Likewise, it has improved energy capacity in the presence of air due to an increased amount of zinc in the cell. The improved air assisted alkaline cell employs a mixture of highly porous manganese dioxide and substantially solid manganese dioxide.
The invention provides a cathode for an air assisted alkaline cell comprising a mixture of porous MnOz and substantially solid Mn02 with the porous MnOz being present in an effective amount to provide air paths into the cathode and thereby recharge the cell in the presence of air.
Still further, the invention provides a cathode for an air assisted alkaline cell comprising a mixture of a porous MnOz and a substantially solid Mn02 having a packing density gradient when shaped into a cathode with the lowest packing density predominating at the portion of the cathode intended to be contacted by air during the operation of the cell.
In another embodiment, the invention provides a composition suitable for use in the manufacture of a cathode for an air assisted alkaline cell comprising a mixture of highly porous Mn02 and substantially solid Mn02 with the highly porous MnOz being present in an amount effective to enable recharging of the cathode prepared from the mixture when used in an air assisted alkaline cell in the presence of air and with the substantially solid MnOz being present in an amount to produce an acceptable alkaline cell in the absence of air.
The invention also includes a cathode prepared from the mixture, as well as the method of preparing the cathode, an air assisted alkaline cell incorporating the cathode and the method of manufacturing the air assisted alkaline cell. More particularly and in line with the above, the invention comprehends a method for preparing aTcathode for use in an air assisted alkaline cell comprising the following steps, mixing a composition comprising porous Mn02 and substantially solid MnOz with the porous MnOz being present in an amount effective to recharge the cathode in the presence of air, forcing the composition into a form, subjecting the composition to pressure while in the form to shape a cathode having a packing gradient with the lowest volume percent of solids being at one end of the cathode and the highest at the other end of the cathode.
Further, the invention provides an air assisted alkaline cell comprising a conductive container for supporting the components of the cell and for forming an external terminal for the cell, a cathode electrode in contact with the inner wall of the container, the cathode comprising a mixture of porous Mn02 and substantially solid Mn02 with the porous Mn02 being present in an effective amount to recharge the cell in the presence of air. An anode electrode comprises metallic zinc, a binder, an electrolyte and a separator electrically isolates the cathode electrode from the anode electrode. An anode current collector is in electrical contact with the anode electrode and an external terminal for the cell is a.n contact with the anode current collector. An aqueous alkaline electrolyte is provided for facilitating the electrochemical reaction a.n the cell and an air permeable seal closes the conductive container and allows oxygen to enter the cell and come in contact with the cathode electrode.
Still further, the invention provides a method for preparing an air assisted alkaline cell comprising the following steps, providing a conductive container for the cell which can serve as the first external terminal for the cell, providing a conductive container for the cell which can serve as the first external terminal for the cell, preparing a mixture of porous Mn02 and substantially solid Mn02, loading the mixture of porous Mn02 and substantially solid MnOz into the container to form a cathode electrode, adding a separator to the container to electrically isolate the cathode electrode from the anode electrode, adding a zinc anode composition to the container in contact with the separator and providing an anode current collector and an air permeable conductive cover for the cell, the conductive cover forming the second external terminal for the cell.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a sectional view of an inverted air assisted alkaline cell of the present invention.
Fig. 2 is an exploded view of the subassembly used in assembling the cell.
Fig. 2A is a plan view of the air permeable seal member used in the subassembly of Fig. 2.
Fig. 3 is a series of curves generated through the continuous discharge of several different cells.
Fig. 4 is a series of curves generated through the intermittent discharge of several different cells.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Fig. 1, the air assisted alkaline cell is assembled in a conventional conductive steel container 11 which also forms an external terminal for the cell. The cathode for the cell 13 is a mixture of highly porous manganese dioxide and substantially solid manganese dioxide. The mixture is prepared in a conventional mixer.
A good source of highly porous manganese dioxide is so-called chemically synthesized manganese dioxide or CMD. CMD
is usually marketed with a porosity of 25~ to 35%.
However, CMD can be prepared in the form of very porous spheres having a porosity of approximately 600. The porous 20~~~~~
1 spheres have a substantial amount of surface available for reaction with oxygen in an air assisted cell. If a cell were prepared using CMD as the only active cathode material the total energy capacity of the cell would be lowered due to the decrease in the amount of Mn02 available per unit volume of cathode.
In order to increase the total energy capacity of the cell in an air free environment, substantially solid Mn02 must be available for the cell reaction. A good source of substantially solid Mn02 is electrolytically deposited Mno2 or EMD. EMD can be obtained in the form of dense particles after the electrolytically deposited material is stripped from the electrodes, crushed and screened. EMD has a porosity of approximately 10%-16% and therefore is a sub-stantially solid material.
Since CMD and EMD are both porous materials with CMD being substantially porous while EMD is substantially solid, the terms CMD or highly porous and EMD or sub-stantially solid will be used to characterize the materials in this specification.
The use of CMD and EMD in the manufacture of cathodes far dry cells has been known for many years. CMD
and EMD have each been mixed with naturally occurring manganese dioxide to forir~ cathodes. To date, the inventor is aware of no one mixing CMD arid EMD for use in the cathode of an air assisted alkaline cell and of the inventive results obtained through the use of a mixture of these materials.
Since in the operation of an air assisted cell the Mn02 is regenerated, only sufficient highly porous MnO~ is necessary to provide good rechargeability of the Mn02 in the ~fl~~5~~
1 presence of air. Tn order to increase the total energy capacity of the cell, EMD can be added to supply additional active cathode material. As the ratio of EMD to CMD
increases, the cel l s air free capacity also increases. The amount of CMD and EMD used in the cathode of the cell depends on the desired parameters of the cell with, for example, more or less CMD being used per cathode depending on the energy capacity desired in the presence of air. For a good sell capacity in an air free environment and good rechargeability in an environment containing air, a mixture of 1:5, that is, one part by weight of CMD to five parts by weight of EMD is preferred.
While CMD is a good source of highly porous manganese dioxide, other sources are available now anra will be available in the future; therefore, the present invention is not so limited. Likewise, EMD is a readily available source of bulk, substantially solid, manganese dioxide, however, other sources are available including naturally occurring manganese dioxide, and even conventionally available low porosity CMD, and, therefore, the present invention is not limited to EMD.
The CMD and EMD are added to the mixer along with a small amount of Teflon, approximately 0.6% by weight of an aqueous solution, which is used to selectively wetproof the 2~ cathode and to improve the stability of the formed electrode structure. Teflon is a trademark of DuPont and is used to identify polytetrafluoroethylene polymeric materials. The selective wetproofing of the Mn02 keeps some of the CMD
surface available for contact with air so that the Mn02-air-electrolyte junction needed for rechargeability is achieved in the finished cell. After thoroughly mixing the 1 components, the cathode composition is poured into a steel container for the cell. An impact extruder is used to load the cell container with the cathode material. Under the pressure of the impact extruder, the cathode material becomes tightly packed about the walls of the container, with the Teflon serving to bind the mixture into a compact mass. Tt has been observed in the manufacture of the cells that a porosity gradient is formed in the manganese dioxide in the cathode, with the highest packing density being at the bottom of the container and with the lowest packing density at the top. The top of the cathode is not as tightly packed as the bottom and, in turn, more of the CMD/EMD mixture is exposed to air access at the top. The packing density of the material at the top of the formed cathode is approximately 70% while the packing density at the bottom is approximately 100%.
It is very important in the operatian of the cathode for t:he air assisted alkaline cell of the present invention th~~t some of the Mn02 be exposed simultaneously to a conductor, to electrolyte and to air. In the Cegasa cell this was achieved through the use of the air distribution grid. No such grid is used or required in the inventive cell with the highly porous Mn02 providing a surface area of Mn02 and air paths into the top of the cathode for the re-charging of the air assisted cell while the substantially solid Mn02 provides the bulk presence of manganese dioxide for the conventional operation of the alkaline cell.
CMD can be prepared starting with manganese ore which is first converted to a nitrate which is then treated with ammonium carbonate and chemical oxidants to form manganese carbonate. The manganese carbonate, after ~0~2~~~
washing, is roasted in the presence of oxygen and chemical oxidants to form manganese dioxide which is purified by washing to obtain the battery grade manganese dioxide material. The preferred CMD used in the preparation of the cathode of the air assisted cell is a material obtained from Sedema which is a division of Sadacam S.A. of Brussels, Belgium. The material is identified by Sedema as Sedema TR
manganese dioxide. The material has a porosity of approx-imately 60%. The EMD is obtained from the electrolytic deposition of manganese dioxide and is supplied by the assignee of the instant application. The EMD can also be purchased fram commercial suppliers. When the materials are combined in a homogeneous mixture, and then added to the container to form the cathode, the preferred average porosity for the cathode is 20%. CMD has a porosity of approximately .13 cc/g while EMD has a porosity of approximately .022 to 0.035 cc/g.
After the cathode is formed in the container, a separator 15 is added to electrically isolate the anode material from the cathodo and the container while still permitting ion transport between the electrodes. The anode material 17 is then added to the separator lined cavity of ...
the cell. The anode material comprises a mixture of zinc powder, a gel forming binder and the liquid electralyte used in the cell. The preferred binder is Carbopol 934 which is a carboxy polymethylene polymer available from the B. F.
Goodrich Company, of Cleveland, Ohio.
In an air assisted cell, the discharged active cathode, that is the manganese dioxide, undergoes a reaction with the air in the cell and with air which can enter the cell to become recharged, reoxidizing the reduced manganese ~0~2~~
1 oxide to manganese dioxide. In the discharge of the alkaline cell, the manganese dioxide is reduced to a lower oxidation state. The oxygen in the air will spontaneously restore or regenerate the higher oxidation state over a period of time. If the cell is subjected to brief periods of high rate discharge, then the cell must be rested for substantial periods of time between each discharge to enable the air to completely recharge the Mno2. However, if the cell is continuously discharged at a rate which is less than the rate at which the Mn02 is recharged by the incoming air, then the air recharges the Mn02 as quickly as it is dis-charged. In other words, regardless of the rate at which the cell is discharged, if the cell is drained at a low rate or is rested for a sufficient period of time, then the cathode's ability to be recharged is limited only by its access to air. The cathode material is regenerated without involving th~3 zinc anode material. Tha zinc is oxidized during the d:lscharge but it cannot be regenerated during a rest period. In view of this, less cathode material needs to be added to an air assisted alkaline cell and, in turn, the volume of zinc can be increased in the cell to increase the overall capacity of the cell.
Returning again to a discussion of Fig. 1, the alkaline electrolyte solution :Ls approximately a 34% to 37%
by weight solution of potassium hydroxide in water. The electrolyte from the anode mixture 17 permeates the separator 15, and the cathode 13. An open area 19 is left in the cell to provide room for expansion of the anode mixture 17.
A subassembly indicated generally by the number 20, referring to Fig. 2, is used to close the cell. The _g_ ~0~~~~ ~~
1 subassembly consists of an anode current collector 21, a seal member 23, an air permeable gasket 25, a neutral cover 27 and a rivet 29 which is used to join the several pieces together.
The anode current collector 21 is made from an electrically conducting metal that is inert to the cell's caustic environment. The collector metal preferably is sheet brass. The anode current collector 21 is rolled to have an arcuate shape. The sheet metal is folded over to form a flat surface which fits tightly against the bottom of the seal member 23. A nail shaped collector is also suitable.
The seal member 23 is made of an organic polymeric material which is compatible with the several components of the cell. The preferred material is polypropylene. The seal member 23 has a substantially flat bottom portion 33 surrounding a sleeve 35. Below and in line with the periphery of 'the bottom portion 33 is a substantially circular projecting first wall portion 37. A plurality of circumferentially spaced spokes 39 extend from the periphery of the bottom portion 33 out to and below a second wall portion 41 extending upwardly away from bottom portion 33.
The spaces 43 between the spokes 39 provide a passage for air to pass through the seal member 23.
A membrane 25 fits within the area of the seal member 23 bounded by the wall 41. The membrane is made of two layers of Teflon. One layer is a nonwoven film and the other is a mesh. The two layers are heat sealed together and form an air permeable membrane for the cell. The gasket 25 can be fastened to the bottom 33 and the spokes 39 by welding. A fatty polyamide adhesive such as the type _9_ 1 disclosed in Winger U.S. Patent 3,922,178 can be used to backup the weld and to prevent electrolyte creep between the polypropylene seal and the microporous gasket. Two beads of the adhesive can be used. One bead is placed around the periphery of the bottom 33 where it joins the inside of the wall 41. The second bead can be placed on the bottom 33 where it joins the outer wall of the sleeve 35.
To further ensure that the microporous gasket 25 stays in position, concentric raised ridges 40 can be formed on the bottom 33 of the seal 23. The gasket 25 will then be clamped between the ridges on the bottom 33 and the neutral cover 27.
The vented neutral cover 27 is preferably made of stainless steel and has a pair of spaced apertures 45 therein to allow the passage of air into the cell. The vented cover 27 will fit within the area of the seal member 23 bounded by the wall 41.
The rivet 29 is preferably made of brass and has a thinned portion 47 which can be easily spread to bind a?..l of the parts of the subassembly 20 together.
The dimensions of the several components of the subassembly 20 and of the overall cell can be varied to meet particular size requirements for the type of cell being assembled.
The subassembly 20 is inserted into the bottom of the inverted cell as shown in Fig. 1. The wall 37 moves the top edge of the separator 15 away from the cathode material 13. The wall 37 and separator 15 protect the anode material 17 from contact with the air entering the cell. This avoids 30 the loss of zinc due to direct reaction with oxygen. The wall portion 41 of the seal assembly 23 insulates the neutral cover 27 from electrical contact with the container 11.
To complete assembly of the cell, a bottom cover 51 is placed into the steel container 11 and is also S isolated from contact with the container by the wall portion 41 of the subassembly 20. The bottom cover 51 makes electrical contacts with the rivet 29, or other suitable electrically conductive means, enabling the bottom cover 51 to become the second external terminal for the cell. The i0 edge of the steel container 11, and of the subassembly 20, are then rolled to hold the upturned portion 53 of the bottom cover 51 locked in position on the bottom of the cell. A gap 55 surrounds the bottom cover 51, separating it from contact with the container 11. The bottom cover 53 1S preferably contains three small apertures 54, two of which are shown in Fig. 1, spaced approximately 12p' apart which provide a pasteage for air to enter into the bottom of the cell. The ai.r can pass through the subassembly 20 and ' contact the top portion of the cathode through the air ' 20 passage 43. The top cover 57 can be fastened to the container by welds 59 after the cathode is rammed into place. It can be added before or after this step as it is merely attached to the container.
Several D-size air assisted alkaline cells of the present invention were tested in 2.2 ohm continuous service tests (Fig. 3). The test results showed that the air assisted cell of the present invention (1) was better than two commercially available alkaline cells (5 and 6) and much better than a commercially available air assisted alkaline 30 cell (3) and an experimental air assisted cell (2). The cell was not as good as an experimental alkaline cell (4).
~~3~a~~
1 The latter result was a function of the amount of cathode material present in the cells with the CMD of the air assisted cell (1) providing less actual Mno2.
Since an air assisted alkaline cell recovers some of its charge while standing between high rate pulsed discharges, a dry cell industry recognized intermittent discharge test was carried out (Fig. 4). In the standard test chosen, the test curves are generated by discharging D-size cells on,a,2.2 ohm load for four minutes per hour, ld eight hours per day. The total discharge time per day was 32 minutes. However, the curve marked 1 was produced by discharging a D-size cell on a 2.2 ohm load for 4 minutes per hour, twenty-four hours a day. The total discharge time per day was 96 minutes. This test regime is identified by the assignee of the present invention by the initials CIT
and is Continuous Intermittent Teat. The impact of using the industry standard test, instead of the CIT regime, is that the cell has much mare time to recover when it is tested for 32 minutes per day instead of 96, minutes per day.
Therefore, one would expect that cell 1, manufactured without an air distribution grid, would provide more service when evaluated on the industry standard test instead of the CIT test. This difference in test schedules is probably the reason for the difference in performance between cell 1, without an air grid, and the cell 2 with an air grid.
In the assembly of the air assisted alkaline cell, the air holes 54 in the external electrode 51 are closed by a suitable seal tab such as that disclosed in U.S. Patent 4,649,090 issued March 10, 1987, to Oltman et al. The seal tab protects the interior of the cell from deleterious 1 environmental conditions and maintains the freshness of the cell.
The preferred label material and configuration for the fully assembled cell is that disclosed in.U.S. latent 4,801,514 issued January 31, 1989, to Will et al. The mufti-layer adhesive label disclosed in the patent is particularly useful far dry cell batteries.
It can be seen from the discussion above that an improved air assisted alkaline cell is provided. The air assisted cell does not require a cathode support or air distribution grid, but instead relies on the porosity of the manganese dioxide to provide paths for air to travel into the electrode and thereby enable recharging of the Mn02 to occur. The poroia air distribution support is also not necessary in this cell, enabling more active materials to be employed in the same size container.
Though the invention has been described with respect to a specific preferred embodiment thereof, many variations and modifications will become apparent to those skilled in the art. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.
Claims (19)
1. A cathode for an air assisted alkaline cell comprising:
a mixture of a porous MnO2 and a substantially solid MnO2 having a packing density gradient when shaped into a cathode with the lowest packing density predominating at the portion of said cathode intended to be contacted by air during the operation of the cell.
a mixture of a porous MnO2 and a substantially solid MnO2 having a packing density gradient when shaped into a cathode with the lowest packing density predominating at the portion of said cathode intended to be contacted by air during the operation of the cell.
2. A cathode for use in an air assisted alkaline cell comprising:
a mixture of a porous MnO2 and a substantially solid MnO2 wherein said mixture is predominantly solid MnO2 in order to provide a cell with a high ampere hour output in the absence of air.
a mixture of a porous MnO2 and a substantially solid MnO2 wherein said mixture is predominantly solid MnO2 in order to provide a cell with a high ampere hour output in the absence of air.
3. A cathode for use in an air assisted alkaline cell as set forth in claim 2, wherein:
said mixture of a porous MnO2 and a substantially solid MnO2 is in an approximate ratio by weight of 1:5 of porous MnO2 to substantially solid MnO2.
said mixture of a porous MnO2 and a substantially solid MnO2 is in an approximate ratio by weight of 1:5 of porous MnO2 to substantially solid MnO2.
4. A cathode for use in an air assisted alkaline cell as set forth in claim 2, wherein:
said porous MnO2 is chemically prepared MnO2 and said substantially solid MnO2 is electrolytically prepared MnO2.
said porous MnO2 is chemically prepared MnO2 and said substantially solid MnO2 is electrolytically prepared MnO2.
5. A cathode for an air assisted alkaline cell comprising a mixture of porous MnO2 and substantially solid MnO2 with said porous MnO2 being present in an effective amount to provide air paths into the cathode and thereby recharge the cell in the presence of air.
6. A cathode for an air assisted alkaline cell comprising a mixture of porous MnO2 and substantially solid MnO2 with the porous MnO2 being present in an amount effective to enable recharging of a cathode prepared from said mixture when used in an air assisted alkaline cell in the presence of air and with the,substantially solid MnO2 being present in an amount to produce an acceptable alkaline cell in the absence of air.
7. A cathode for use in an air assisted alkaline cell as set forth in claim 6, wherein:
said mixture of a porous MnO2 and a substantially solid MnO2 is in an approximate ratio by weight of 1:5 porous MnO2 to substantially solid MnO2.
said mixture of a porous MnO2 and a substantially solid MnO2 is in an approximate ratio by weight of 1:5 porous MnO2 to substantially solid MnO2.
8. A cathode for use in an air assisted alkaline cell as set forth in claim 6 wherein:
said mixture of a porous MnO2 and a substantially solid MnO2 is predominantly substantially solid MnO2.
said mixture of a porous MnO2 and a substantially solid MnO2 is predominantly substantially solid MnO2.
9. A method for preparing a cathode for use in an air assisted alkaline cell comprising the following steps:
mixing a composition comprising porous MnO2 and substantially solid MnO2 with the porous MnO2 being present in an amount effective to recharge said cathode in the presence of air;
forcing said composition into a form;
subjecting said composition to pressure while in said form to shape a cathode having a packing gradient with the lowest volume percent of solids being at one end of said cathode and the highest at the other end of said cathode.
mixing a composition comprising porous MnO2 and substantially solid MnO2 with the porous MnO2 being present in an amount effective to recharge said cathode in the presence of air;
forcing said composition into a form;
subjecting said composition to pressure while in said form to shape a cathode having a packing gradient with the lowest volume percent of solids being at one end of said cathode and the highest at the other end of said cathode.
10. A method for preparing a cathode as set forth in claim 9, wherein an impact extrusion machine is used to subject said cathode to pressure.
11. An air assisted alkaline cell comprising:
a conductive container for supporting the components of said cell and for forming an external terminal for said cell;
a cathode electrode in contact with the inner wall of said container, said cathode comprising a mixture of porous MnO2 and substantially solid MnO2 with said porous MnO2 being present in an effective amount to recharge the cell in the presence of air;
an anode electrode, said anode electrode comprising metallic zinc, a binder and an electrolyte;
a separator for electrically isolating said cathode electrode from said anode electrode;
an anode current collector in electrical contact with said anode electrode;
an external terminal for said cell in contact with said anode current collector;
an aqueous alkaline electrolyte for facilitating the electrochemical reaction in said cell; and an air permeable seal for closing said conductive container and for allowing oxygen to enter the cell and come in contact with said cathode electrode.
a conductive container for supporting the components of said cell and for forming an external terminal for said cell;
a cathode electrode in contact with the inner wall of said container, said cathode comprising a mixture of porous MnO2 and substantially solid MnO2 with said porous MnO2 being present in an effective amount to recharge the cell in the presence of air;
an anode electrode, said anode electrode comprising metallic zinc, a binder and an electrolyte;
a separator for electrically isolating said cathode electrode from said anode electrode;
an anode current collector in electrical contact with said anode electrode;
an external terminal for said cell in contact with said anode current collector;
an aqueous alkaline electrolyte for facilitating the electrochemical reaction in said cell; and an air permeable seal for closing said conductive container and for allowing oxygen to enter the cell and come in contact with said cathode electrode.
12. An air assisted alkaline cell as set forth in claim 11, wherein:
said cathode has a packing density gradient with the lowest percentage of solids predominating at the portion of the cathode contacted by air during the operation of said cell.
said cathode has a packing density gradient with the lowest percentage of solids predominating at the portion of the cathode contacted by air during the operation of said cell.
13. An air assisted alkaline cell as set forth in claim 11, wherein:
said cathode is a 1:5 mixture by weight of porous MnO2 to substantially solid MnO2.
said cathode is a 1:5 mixture by weight of porous MnO2 to substantially solid MnO2.
14. An air assisted alkaline cell as set forth in claim 11, wherein:
said porous MnO2 is chemically prepared MnO2 and said substantially solid MnO2 is electrolytically deposited MnO2.
said porous MnO2 is chemically prepared MnO2 and said substantially solid MnO2 is electrolytically deposited MnO2.
15. An air assisted alkaline cell as set forth in claim 11, wherein:
said aqueous alkaline electrolyte is an aqueous solution of potassium hydroxide.
said aqueous alkaline electrolyte is an aqueous solution of potassium hydroxide.
16. A method for preparing an air assisted alkaline cell comprising the following steps:
providing a conductive container for the cell which can serve as the first external terminal for said cell;
preparing a mixture of porous MnO2 substantially solid MnO2 loading; said mixture of porous MnO2 and substantially solid MnO2 into said container to form a cathode electrode;
adding a separator to said container to electrically isolate said cathode electrode from the anode electrode;
adding a zinc anode composition to said container in contact with said separator; and providing an anode current collector and an air permeable conductive cover for said cell, said conductive cover forming the second external terminal for said cell.
providing a conductive container for the cell which can serve as the first external terminal for said cell;
preparing a mixture of porous MnO2 substantially solid MnO2 loading; said mixture of porous MnO2 and substantially solid MnO2 into said container to form a cathode electrode;
adding a separator to said container to electrically isolate said cathode electrode from the anode electrode;
adding a zinc anode composition to said container in contact with said separator; and providing an anode current collector and an air permeable conductive cover for said cell, said conductive cover forming the second external terminal for said cell.
17. A method for preparing an air assisted alkaline cell as set forth in claim 16, wherein:
said mixture of porous MnO2 and substantially solid MnO2 is mixed in a ratio which is predominantly substantially solid MnO2.
said mixture of porous MnO2 and substantially solid MnO2 is mixed in a ratio which is predominantly substantially solid MnO2.
18. A method for preparing an air assisted alkaline cell as set forth in claim 16, wherein:
said mixture of porous MnO2 and substantially solid MnO2 is mixed in a 1:5 ratio by weight of porous MnO2 to substantially solid MnO2.
said mixture of porous MnO2 and substantially solid MnO2 is mixed in a 1:5 ratio by weight of porous MnO2 to substantially solid MnO2.
19. A method for preparing an air assisted alkaline cell as set forth in claim 16, wherein:
said anode composition comprises a mixture of zinc powder and a binder.
said anode composition comprises a mixture of zinc powder and a binder.
Applications Claiming Priority (2)
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|---|---|---|---|
| US477,418 | 1990-02-09 | ||
| US07/477,418 US5079106A (en) | 1990-02-09 | 1990-02-09 | Air assisted alkaline cells |
Publications (2)
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|---|---|
| CA2032530A1 CA2032530A1 (en) | 1991-08-10 |
| CA2032530C true CA2032530C (en) | 2001-10-16 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002032530A Expired - Lifetime CA2032530C (en) | 1990-02-09 | 1990-12-18 | Air assisted alkaline cells |
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| US (1) | US5079106A (en) |
| EP (1) | EP0441592B1 (en) |
| JP (1) | JP3265430B2 (en) |
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| DE (1) | DE69132116T2 (en) |
| DK (1) | DK21791A (en) |
| SG (1) | SG49920A1 (en) |
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| US4121018A (en) * | 1976-08-09 | 1978-10-17 | Meer Danilovich Kocherginsky | Positive electrode for air-depolarized alkaline primary cell with thickened electrolyte |
| US4105830A (en) * | 1977-08-01 | 1978-08-08 | Union Carbide Corporation | Air depolarized cell |
| US4433035A (en) * | 1981-10-26 | 1984-02-21 | Duracell Inc. | Catalytic cathode composition for air-depolarized cell and method of preparation |
| JPS59171468A (en) * | 1983-03-18 | 1984-09-27 | Matsushita Electric Ind Co Ltd | Method for manufacturing air electrode and its catalyst |
| US4608279A (en) * | 1984-12-27 | 1986-08-26 | Union Carbide Corporation | Galvanic cells having ion exchange resin in their cathode mix |
| DE3722019A1 (en) * | 1987-07-03 | 1989-01-12 | Varta Batterie | METHOD FOR PRODUCING A PLASTIC-BONDED GAS DIFFUSION ELECTRODE USING A MANGANOXIDE CATALYST OF THE PRIMARY COMPOSITION MNO (DOWN ARROW) 2 (DOWN ARROW) (DOWN ARROW * DOWN ARROW) 8 (DOWN ARROW) INCLUDED |
| US4894296A (en) * | 1987-10-27 | 1990-01-16 | Duracell Inc. | Cathode for zinc air cells |
-
1990
- 1990-02-09 US US07/477,418 patent/US5079106A/en not_active Expired - Lifetime
- 1990-12-18 CA CA002032530A patent/CA2032530C/en not_active Expired - Lifetime
-
1991
- 1991-02-04 JP JP09989591A patent/JP3265430B2/en not_active Expired - Fee Related
- 1991-02-05 EP EP91300931A patent/EP0441592B1/en not_active Expired - Lifetime
- 1991-02-05 SG SG1996009188A patent/SG49920A1/en unknown
- 1991-02-05 DE DE69132116T patent/DE69132116T2/en not_active Expired - Fee Related
- 1991-02-06 KR KR1019910002008A patent/KR910016105A/en not_active Ceased
- 1991-02-08 DK DK021791A patent/DK21791A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0441592A3 (en) | 1991-12-04 |
| KR910016105A (en) | 1991-09-30 |
| DE69132116T2 (en) | 2000-11-16 |
| EP0441592B1 (en) | 2000-04-19 |
| DK21791A (en) | 1991-08-10 |
| JP3265430B2 (en) | 2002-03-11 |
| DK21791D0 (en) | 1991-02-08 |
| EP0441592A2 (en) | 1991-08-14 |
| CA2032530A1 (en) | 1991-08-10 |
| US5079106A (en) | 1992-01-07 |
| SG49920A1 (en) | 1998-06-15 |
| JPH04230965A (en) | 1992-08-19 |
| HK1007095A1 (en) | 1999-04-01 |
| DE69132116D1 (en) | 2000-05-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed | ||
| MKEC | Expiry (correction) | ||
| MKEC | Expiry (correction) |
Effective date: 20121202 |