Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Cell enclosure structure – e.g. – housing – casing – container,...
Reexamination Certificate
2000-01-19
2001-08-07
Brouillette, Gabrielle (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Cell enclosure structure, e.g., housing, casing, container,...
C429S072000, C429S164000, C429S176000
Reexamination Certificate
active
06270921
ABSTRACT:
BACKGROUND
This invention generally relates to air recovery electrochemical cells.
Batteries are commonly used electrical energy sources. A battery contains a negative electrode, typically called an anode, and a positive electrode, typically called a cathode. The anode contains an active material that can be oxidized; the cathode contains an active material that can be reduced. The anode active material is capable of reducing the cathode active material. In order to prevent direct reaction of the anode material and the cathode material, the anode and the cathode are electrically isolated from each other by a separator.
When the battery is used as an electrical energy source in a device, electrical contact is made to the anode and the cathode, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power. An electrolyte in contact with the anode and the cathode contains ions that flow through the separator between the electrodes to maintain charge balance throughout the battery during discharge.
An air recovery battery, also known as an air assisted or air restored battery, is a battery that uses air to recharge its cathode during periods of low or no discharge. One type of air recovery battery employs zinc powder as the anode, manganese dioxide (MnO
2
) as the cathode, and an aqueous solution of potassium hydroxide as the electrolyte. At the anode, zinc is oxidized to zincate:
Zn+4OH
−
→Zn(OH)
4
2−
+2
e
−
At the cathode, MnO
2
is reduced to manganese oxyhydrate:
MnO
2
+H
2
O+
e
−
→MnOOH+OH
−
When the cell is not in use or when the rate of discharge is sufficiently slow, atmospheric oxygen enters the cell and reacts with the cathode. Manganese oxyhydrate is oxidized to form MnO
2
:
½O
2
+MnOOH→MnO
2
+OH
−
During high rates of discharge, air recovery batteries operate like conventional alkaline cell by reducing “fresh” (unreduced) MnO
2
. During low rates of discharge and periods of rest with no current flow, the “consumed” (reduced) MnO
2
is restored or recharged by atmospheric oxygen to the fresh state. Since oxygen must reach the MnO
2
for recharging, the cathode of the battery must not be wetted completely by electrolyte. If the cathode is soaked with wet electrolyte, air transport properties inside the cathode degrade and recharging of MnO
2
is hampered.
A prismatic battery can be generally rectangularly shaped. For example, a prismatic battery can be relatively flat with two parallel rectangularly-shaped faces, making them suitable for use in cellular telephones. More broadly, a prismatic battery can be shaped as a polyhedron with two polygonal faces lying in parallel planes and with the other faces as parallelograms. For example, if the polygonal faces are rectangular, then the battery is shaped as a rectangular prism. If the polygonal faces are circular, then the battery is shaped as a circular prism.
SUMMARY OF THE INVENTION
In one aspect, the invention features prismatic air recovery batteries in which the cathode recharges during periods of low or no discharge. The batteries generally provide good air distribution to the cathode and can be manufactured with conducting or non-conducting cans having thin profiles. The batteries can be stacked together to provide high voltages.
In another aspect, the invention features an air recovery battery including a central longitudinal axis and a cathode having a major surface normal to the central longitudinal axis. The battery can further include a cathode can having at least one air access opening having a central longitudinal axis, wherein the cathode includes a major surface normal to the longitudinal axis of the opening.
In another aspect, the invention features an air recovery battery including a cathode can having sides with outer surfaces; a cathode disposed inside the cathode can; a separator adjacent to the cathode; an anode can having sides with outer surfaces; and an anode disposed inside the anode can; wherein the cathode can and the anode can are sealed together such that the outer surfaces of the sides of the cans are substantially flush. The battery can further include at least one air access opening in the cathode can.
In another aspect, the invention features a method of assembling an air recovery battery including (a) placing anode material in an anode can having sides, the sides having outer surfaces; (b) placing a cathode in a cathode can having sides, the sides having outer surfaces; (c) placing a separator in the cathode can; and (d) sealing the anode can and the cathode can together such that the outer surfaces of the sides of the cans are substantially flush. The method can further include placing a membrane in the cathode can, providing at least one air access opening in the cathode can, and/or providing an anode current contact on the anode can. Furthermore, the anode can and the cathode can can be sealed by mechanical crimping. The membrane can be laminated or glued to the cathode can.
Other features and advantages of the invention will be apparent from the description of the preferred embodiment thereof, and from the claims.
REFERENCES:
patent: 3902922 (1975-09-01), Kainiki-Kis
patent: 4041211 (1977-08-01), Wiacek
patent: 4105830 (1978-08-01), Kordesch
patent: 5328778 (1994-07-01), Woodruff et al.
patent: WO 00/36693 (2000-06-01), None
patent: WO 00/36689 (2000-06-01), None
Kaplan Alexander
Vu Viet
Brouillette Gabrielle
Fish & Richardson P.C.
The Gillette Company
Wills Monique
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