Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Include electrolyte chemically specified and method
Reexamination Certificate
1999-07-29
2001-04-17
Weiner, Laura (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Include electrolyte chemically specified and method
C429S218100, C429S215000, C429S231700, C429S231800, C429S231950
Reexamination Certificate
active
06218055
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to electrochemical power cells (that is, batteries) and to a method for improving electrochemical power cell performance, and, more particularly, to electrochemical power cells having a cathode comprising a fluorine compound, to electrochemical power cells comprising an organic, sulfur-containing electrolyte solvent and to electrochemical power cells comprising a cobalt trifluoride cathode, a lithium anode and a chelating agent within the electrolyte to chelate cobalt ions.
BACKGROUND OF THE INVENTION
A class of primary electrochemical power cells which incorporates lithium as the anode material and solid or liquid oxidizers as cathode materials is a commercially available source of power in a small, portable package. These lithium cells have theoretical output voltages in the range of 3 to 3.9 volts and theoretical specific energies in the range of 1000 to 2000 Wh/kg. These cells require nonaqueous electrolytes because of the reactivity of lithium in aqueous solutions. Examples of practical lithium cells are lithium carbon monofluoride (3.1 V), lithium sulfur dioxide (3.1 V), lithium manganese dioxide (3.5 V), lithium thionyl chloride (3.6 V) and lithium sulfuryl chloride (3.9 V). See U.S. Pat. Nos. 3,536,532, 3,567,515, and 4,400,453 The output voltage of 3.9 V for the lithium sulfuryl chloride cell is believed to be the highest output voltage achievable in small, portable commercially available electrochemical power cells.
The lithium anode is stable in these cells because a protective film forms on the lithium surface either by direct reaction with the electrolyte or with an additive in the electrolyte. See U.S. Pat. Nos. 3,567,515 and 4,400,453. In commercially available lithium/thionyl chloride and lithium/sulfuryl chloride electrochemical power cells, for example, the protective film produced by the reaction between the lithium and an oxyhalide electrolyte is lithium chloride. These films are typically good ionic conductors for lithium ions, but do not transport species present in the electrochemical power cell that could damage the lithium anode.
These lithium electrochemical power cells are commercially viable only because a mechanically stable electrode of blended carbon black and Teflon® was developed on which solid, liquid or soluble cathode materials could be efficiently reduced. A “solid” cathode material is incorporated into the blend of carbon black and Teflon®. A “liquid” cathode material may be the solvent component of the electrolyte. A “soluble” cathode material is dissolved in the electrolyte. The process of fabricating carbon black-Teflon® electrodes for commercial lithium cells is well established and is described, for example, in Turk, C.,
Modern Battery Technology,
p. 291 (1991).
For a number of uses, it is desirable to develop electrochemical power cells with output voltages and specific energies greater than possible with currently available electrochemical power cells.
SUMMARY OF THE INVENTION
The present invention provides generally an electrochemical power cell comprising an anode, a cathode comprising a fluorine compound and an electrolyte to maintain ionic conductivity between the anode and the cathode. Preferably, the water content of the fluorine compound is less than approximately 150 parts per million (ppm). More preferably, the water content of the fluorine compound is less than approximately 100 ppm. Most preferably, the water content of the fluorine compound is less than approximately 50 ppm. The fluorine compound is preferably present as a single phase with a purity of at least approximately 99%.
A number of fluorine compounds, including metal fluoride compounds, nitrosonium fluoride compounds or oxyfluoride compounds are suitable for use in the cathodes of the present invention. Preferably, the fluorine compound is chosen to provide an output voltage of at least approximately 4.0 V. For example, the fluorine compound can be CoF
3
, AgF
2
, XeF
2
, NO
2
SbF
6
, NO
2
BF
4
, or SbF
5
S. In one preferred embodiment, the fluorine compound is CoF
3
. In another preferred embodiment, the fluorine compound is NO
2
SbF
6
. The nitrosonium fluoride compounds act as soluble cathodes.
The anode of the present invention preferably comprises an alkali metal or an alkali earth metal. Most preferably, the anode comprises lithium metal.
The present inventors have discovered that the small, portable electrochemical power cells of the present invention preferably provide a voltage of at least approximately 4.0 V. Indeed, voltages of over approximately 5.0 V are preferably achieved. Moreover, the electrochemical power cells of the present invention preferably provide a specific energy of the cathode material of at least approximately 1000 Wh/Kg (Watt·hours per Kilogram). Specific energy as used herein refers generally to the ratio of energy available from a cell to the weight of the cathodic material in a cell (that is, the weight of the fluorine compound).
Given the relatively high voltages achieved in the electrochemical power cells of the present invention, the electrolyte is preferably stable at voltages of at least approximately 4.0 V and, more preferably, at voltages of at least approximately 5.0 V. The electrolyte solvent should also exhibit low chemical reactivity to other components of the electrochemical power cell (for example, the anode, the cathode and the housing). The electrolyte solvent should also exhibit low solubility for the cell reactants and reaction products.
In one embodiment, alkyl carbonates such as ethylene carbonate and dimethyl carbonate are used as solvents (that is, electrolyte solvents) in the electrochemical power cells of the present invention. More preferably, the electrolyte solvent comprises an organic, sulfur compound or sulfur-containing compound such as a sulfone compound, a sulfolane compound and/or a sulfite compound.
Preferably, the cathode comprises a binder material, carbon and the fluorine compound. The binder material, the carbon and the fluorine compound are preferably ball milled and pressed to form the cathode under substantially dry conditions. Preferably, the water content of the binder material, the carbon and the fluorine compound is each less than 150 ppm. More preferably, the water content of the binder material, the carbon and the fluorine compound is each less than 100 ppm. Most preferably, the water content of the binder material, the carbon and the fluorine compound is each less than 50 ppm. The content of the binder material in the cathode preferably ranges between approximately 5 and approximately 10 weight percent. The content of the carbon in the cathode preferably ranges between approximately 10 and approximately 40 weight percent. The content of the fluorine compound in the cathode preferably ranges between approximately 50 and approximately 85 weight percent. The binder material preferably comprises polytetrafluorethylene. Preferably, the binder material is Teflon® 6C available from DuPont. The carbon is preferably acetylene black.
The binder material, the carbon, and the fluorine compound are preferably pressed onto a conductive current collector. The conductive current collector is preferably fabricated from aluminum, stainless steel or nickel. Other acceptable materials for the conductive current collector include titanium or vanadium.
The fluorine compounds of the present invention are typically very powerful oxidizing agents. In the case that alkyl carbonates such as ethylene carbonate and dimethyl carbonate are used as solvents, the electrochemical power cells of the present invention preferably further comprise at least one separator placed in the electrolyte between the cathode and the anode to slow or reduce migration of cathodic material to the anode. Preferably, such separators are fabricated from a porous material such as Gore-Tex®, available from W. L. Gore & Associates, Celgard®, available from Hoechst Celanese, Corp. or Zircar®, available from Zircar Products Inc. Preferably, a first separator is provided adjacent the c
Bis Richard F.
Bytella Joseph J.
Kronenberg Marvin L.
Meshri Dayal T.
Shah Pinakin M.
Bartony, Jr. Henry E.
Mine Safety Appliances Company
Uber James G.
Weiner Laura
LandOfFree
Electrochemical power cells and method of improving... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrochemical power cells and method of improving..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrochemical power cells and method of improving... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2538723