Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1999-07-15
2001-07-10
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S218100, C429S231100
Reexamination Certificate
active
06258486
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates in general to electrochemical cells, and more particularly, to an electrochemical cell having an electrode with a modified surface layer. The present invention is further directed to a process for fabricating the same.
2. Background Art
Lithium based electrochemical cells have been known in the art for several years. Furthermore, experimentation associated with lithium based cells having intercalation type electrodes has been explored. While batteries utilizing intercalation type electrodes have exhibited some promising performance characteristics, compatibility between the active material layer of such electrodes and associated electrolyte remains largely problematic. For example, electrochemical cells based on lithiated transition metal oxide electrodes de-intercalate lithium ions at relatively high potentials in order to utilize their full capacity—above approximately 4 volts. This high charge voltage coupled with the naturally oxidizing character of the active material facilitates decomposition of the associated electrolyte. Such decomposition of the electrolyte, among other things, adversely affects coulombic efficiency, decreases net capacity as well as increases self-discharge rates of the cell.
It is therefore as object of the present invention to provide an electrode structure and associated fabrication process that remedies, among other things, the aforementioned detriments and/or complications associated with intercalation type electrodes.
SUMMARY OF THE INVENTION
The present invention is directed to an electrode for use in an electrochemical cell comprising: a) a current collecting substrate; b) an active material associated with the substrate; and c) a surface modifying component applied to at least a portion of the active material, wherein the surface modifying component is fabricated from at least one of the group consisting essentially of lithium niobates and lithium tantalates.
In a preferred embodiment of the invention, the electrode further comprises means for increasing the compatibility of the electrode with an associated electrolyte. In this embodiment the compatibility increasing means comprises the surface-modifying component.
In another preferred embodiment of the invention, the surface modifying component is fabricated from a lithium niobate species or lithium tantalate species having the chemical structure Li
x
NbO
y
or Li
x
TaO
y
, wherein x and y range from about 1 to 5.
In yet another preferred embodiment of the invention, the surface-modifying component is in a crystalline or glassy state.
Preferably the surface modifying component is doped with at least one carbonaceous particle and/or at least one additive selected from the group consisting essentially of transition metal oxides, metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
The present invention is also directed to a process for manufacturing an electrochemical cell comprising the steps of: a) associating a surface modifying component with an active material; b) modifying the surface of the active material c) fabricating a first electrode by applying the surface modified active material to a current collecting substrate; d) fabricating a second electrode; and e) associating at least one electrolyte with the first and second electrodes.
In a preferred embodiment of the invention, the step of associating the surface modifying component includes the steps of: a) dissolving at least one of a lithium niobate species and a lithium tantalate species in a solvent and, in turn, preparing a solution; b) applying the prepared solution to the active material; and c) substantially removing the solvent from the solution.
In another preferred embodiment of the invention the step of preparing the solution includes the step of doping the solution with at least one carbonaceous species and/or the step of doping the solution with at least one of the group of transition metal oxides, non-metal oxides, rare earth metal oxides, and metal phosphates, sulfates, and sulfides.
REFERENCES:
patent: 4465747 (1984-08-01), Evans
patent: 6063142 (2000-05-01), Kawakami et al.
A. Manthiram and J. Kim, “Low Temperature Synthesis of Insertion Oxides for Lithium Batteries”Chem. Mater.1998, vol. 10, p. 2895-2909 no month.
R.W. Schwartz, D.A. Payne and A.J. Holland, “The Effects of Hydrolysis and Catalysis Conditions on the Surface Area and Decomposition Behavior of Polymeric Sol-Gel Derived PbTiO3Powders”Ceram. Powder Process Sci., Proc. Int. Conf. 2nd, 1989, p. 165-172 no month.
Fauteux Denis G.
Krawiec Wlodek T.
Chaney Carol
Factor & Partners
Mitsubishi Chemical Corporation
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