Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Patent
1981-12-07
1983-09-20
Walton, Donald L.
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
296235, H01M 1032, H01M 1004
Patent
active
044056982
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to silver oxide cells. The silver oxide cell is a silver (II) oxide cell dischargeable on the single voltage level in a manner like a silver (I) oxide cell.
TECHNICAL BACKGROUND
The silver (II) oxide (AgO) has a power in the order of about 3,200 mAH/cm.sup.3 and its power is higher than that of the silver (I) oxide (Ag.sub.2 O) that has a power in the order of about 1,600 mAH/cm.sup.3. The silver (II) oxide, accordingly, is considered to be advantageous as an active material for the cell cathode from the viewpoint of a cell efficienty and cost as compared to the silver (I) oxide. In instances where the silver (II) oxide is applied to a cell, however, the silver (II) oxide (AgO) is converted into the silver (I) oxide and presents a two-stage discharge curve. The two-stage discharge curve is disadvantageous for numerous small size cells which are employed as an electric source for digital devices, quartz watches or the like that require the discharge on the single voltage level.
Heretofore, extensive studies have been made of the discharge of AgO. For example, Wales and Burbank report in J. Electrochem. Soc., 106-1959, that, even if a considerable amount of AgO would remain, the discharge voltage curve represents a single voltage corresponding to the discharge of Ag.sub.2 O after the surface of AgO is covered thoroughly with Ag.sub.2 O with discharging. Dirkse also observes in J. Electrochem. Soc., 109-1962, that AgO pellets with their surfaces reduced electrochemically to Ag.sub.2 O can show the same voltage as Ag.sub.2 O does. That is, if the AgO pellets are discharged until their surfaces are covered thoroughly with Ag.sub.2 O, it is found that their voltages can be determined by the amount of the Ag.sub.2 O present on the surfaces thereof even if AgO would remain in a considerably large amount. It has thus been found that, in order to form a silver oxide cell dischargeable on the single voltage level from silver (II) oxide in such a manner as Ag.sub.2 O cells, AgO pellets are previously disharged to some extent and cause their surfaces to be covered with Ag.sub.2 O. Various approaches applying this technology have heretofore been proposed. There are methods, such as, for example, a method involving compression molding Ag.sub.2 O powders on small-sized AgO pellets that had been previously prepared, and a method involving covering surfaces of AgO pellets with a mixture of silver (I) oxide powders with silver powders. However, the processes which involve covering AgO pellets with Ag.sub.2 O or Ag and leading by such mechanical means to the state in which the AgO pellets are discharged to some extent offer drawbacks that they are inappropriate for large-scale production and that workability is poor.
In order to improve those drawbacks, some processes have been proposed which involve introducing a reducing material such as Zn, Cd or the like into AgO pellets or a method involving adding a reducing organic material such as formaldehyde, reducing sugar or the like in an electrolyte, thereby leading to a state in which the AgO surface is reduced or discharged. Although these processes can alleviate those drawbacks with respect to workability and large-scale production, they present other disadvantages that the surface of AgO is reduced to a considerable depth to Ag.sub.2 O and further to Ag and cause the silver (II) oxide to be reduced too much, thereby giving rise to a decrease in a discharge performance. In this case, it is also known that lower than about 10% of capacity has already been discharged after the cell assembly. These result in that part of the energy inherent in AgO has been lost from the cell.
DISCLOSURE OF INVENTION
The silver oxide cells in accordance with the present invention comprises an enclosure of a layer of a cathodic material comprising AgO, a layer of a reducing material capable of reducing to AgO and disposed adjacent to the cathodic material layer, a layer of an anodic material and a layer of an electrolyte.
In accordance with a pr
REFERENCES:
patent: 3615858 (1971-10-01), Soto-Krebs
patent: 3655450 (1972-04-01), Soto-Krebs
O'Brien Cornelius F.
Sony Eveready Inc.
Walton Donald L.
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