Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
2000-07-06
2003-10-28
Phasge, Arun S. (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C205S533000, C429S224000, C423S605000
Reexamination Certificate
active
06638401
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrolytic manganese dioxide for use as the cathode in batteries and methods of producing the electrolytic manganese dioxide. More particularly, the present invention provides electrolytic manganese dioxide which when utilized in batteries imparts higher discharge capacity at high discharge rates thereto.
2. Description of the Prior Art
Electrolytic manganese dioxide, referred to in the industry as EMD, is widely used as the cathode material in batteries. EMD was first utilized in zinc-carbon cells (Leclanche cells), and later in alkaline cells.
EMD is used in alkaline batteries to achieve high voltages, low polarization and high discharge capacities. The discharge capacity of alkaline batteries is dependent upon the quality of the EMD utilized. The mixture forming the cathode in alkaline batteries is about 82% EMD and is generally formed into an annular cathode by impact extrusion in the container or by the compression molding of pellets which are recompacted against the container. In both of these processes, the properties of the EMD must be very consistent to allow the battery manufacturer to consistently produce high quality batteries. Alkaline batteries have a higher capacity per unit volume than other zinc-manganese dioxide batteries, and are particularly capable of high discharge capacity, i.e., long life, at high discharge rates.
To achieve the EMD purity required in its production utilizing the well known electrolysis method, a highly purified manganese sulfate solution must be provided to the electrolytic cell. In addition, the electrolytic cell must be operated within a narrow range of process conditions.
By the end of the 1980's, EMD was developed having what was thought to be a satisfactory discharge capacity at the then maximum discharge rates demanded by portable devices, i.e., about 0.5 watt. However, during the past several years, the development of lap-top computers, video cameras, cellular phones and the like have brought about a demand for high discharge capacity at higher discharge rates, i.e., from 1 to 2 watts. While some improvements in battery performance at high discharge rates have been made, EMD has not changed significantly in discharge capacity or in the process conditions utilized in its production for many years. Thus, there is a continuing need for better, higher quality EMD whereby alkaline and other batteries utilizing the EMD have higher discharge capacities at the higher discharge rates presently required.
SUMMARY OF THE INVENTION
The present invention provides improved high quality EMD for use as cathode material in batteries of high discharge capacity at high discharge rates and methods of producing such EMD by electro-deposition in an electrolytic cell. The electrolytic cell includes cathodic and anodic electrodes disposed therein through which an electric current is passed. In accordance with the methods of the present invention, a heated aqueous electrolyte solution comprising sulfuric acid and manganese sulfate is maintained in the electrolytic cell. The solution is of high purity and includes manganese sulfate therein in an amount whereby manganese is present in the range of from about 5 to about 50 grams of manganese per liter of solution. An electric current is applied to the cathodic and anodic electrodes and the electrolyte solution whereby the anodic electrode current density is in the range of from about 2.5 to about 6 amperes per square foot, and the high discharge capacity EMD produced is deposited on the anode.
The temperature of the electrolyte solution in the electrolytic cell is carefully maintained in the range of from about 95° C. to about 98° C. Also, the sulfuric acid concentration in the electrolyte solution is maintained in an amount in the range of from about 20 to about 50 grams of sulfuric acid per liter of solution.
The cathode utilized in the electrolytic cell is preferably comprised of copper, graphite or steel, as determined by cost. The anode is preferably comprised of titanium to provide minimum weight and volume, maximum strength, minimum weight loss, and adequate corrosion resistance.
It is, therefore, a general object of the present invention to provide improved electrolytic manganese dioxide having higher discharge capacity at high discharge rates and methods of producing the same.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
REFERENCES:
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patent: 5580681 (1996-12-01), Fleischer
patent: 5607796 (1997-03-01), Jacus et al.
patent: 5731105 (1998-03-01), Fleischer et al.
patent: 5866278 (1999-02-01), Sumida et al.
patent: 6143446 (2000-11-01), Davis et al.
patent: 6225009 (2001-05-01), Fleischer et al.
patent: 6527941 (2003-03-01), Andersen et al.
Andersen Terrell Neils
Burkhardt Samuel Faust
Howard, Jr. Wilmont Frederick
Kazerooni Vahid
Moumenzadeh Mohammad Reza
Kerr-McGee Chemical LLC
McAfee & Taft
Phasge Arun S,.
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