Chemistry: electrical current producing apparatus – product – and – Sealed cell having gas prevention or elimation means – Prevention or elimination means is one of the cell...
Utility Patent
1998-12-10
2001-01-02
Nuzzolillo, Maria (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Sealed cell having gas prevention or elimation means
Prevention or elimination means is one of the cell...
C429S057000, C429S105000
Utility Patent
active
06168878
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to secondary electrochemical cells, and more particularly, to lithium electrochemical cells having metallic current collectors and associated fabrication and chemical processes utilizing an in situ reduced additive which substantially precludes gas formation within the cell as a result of decomposition of solvents used in association with the electrolyte, and, wherein the additive itself is substantially precluded from forming a gas from its own decomposition during cell cycling and storage.
2. Background Art
Lithium batteries have been known in the art for several years. Furthermore, lithium batteries using liquid, gel, polymer, or plastic electrolytes which utilize metallic current collectors are likewise well known. While such electrolytes have been readily utilized, problems have been identified with respect to commercial solvents, utilized within the electrolyte, decomposing during cell cycling and storage. In particular, without the presence of at least a conventional additive within the cell to form a passivating layer, the solvent reacts with the electrode interface and partially decomposes during cycling and storage. Such a decomposition results in the formation of significant amounts of gas which adversely affect the cell's electrochemical performance, especially coulombic efficiency.
Although conventional additives have been used to form a passivating layer which substantially blocks the solvent from contact with the electrode, problems nevertheless persist. Specifically, the additive itself undergoes decomposition during cell cycling and storage, and, such decomposition likewise results in the generation of significant amounts of gas within the cell.
SUMMARY OF THE INVENTION
The present invention is directed to an electrochemical cell having a controlled electrode surface comprising a first electrode and a second electrode wherein at least one of the first and second electrodes includes a metallic current collector having a surface, an electrolyte including at least one solvent, and an additive or a reduced additive associated with the surface of the metallic current collector. The reduced additive is substantially insoluble in the electrolyte and is preferably reduced in situ.
The invention also includes passivating means including the additive or reduced additive for substantially precluding contact between the solvent of the electrolyte and the surface of the metallic current collector to, in turn, substantially prevent gas formation within the cell, which would otherwise result from decomposition of the solvent upon contact with the surface of the metallic current collector. Means are associated with the additive or reduced additive for substantially precluding gas formation within the electrochemical cell as a result of decomposition of the additive or reduced additive near the surface of the metallic current collector during cell cycling and storage. In a preferred embodiment of the invention, the electrochemical cell exhibits a first cycle coulombic efficiency greater than 91% and a first through tenth cycle coulombic efficiency greater than 85%.
In yet another preferred embodiment, the invention includes means for substantially precluding dendrite formation near the surface of the metallic current collector.
The present invention is also directed to a process for manufacturing an electrochemical cell comprising the steps of: a) fabricating a first and a second electrode wherein at least one of the electrodes includes a metallic current collector having a surface; b) associating at least one electrolyte, having at least one solvent, with the first and second electrodes; and c) associating an additive with at least one of the electrolyte or the surface of the at least one metallic current collector.
The present invention is also directed to a chemical process for an electrochemical cell comprising the steps of: a) fabricating a first and a second electrode wherein at least one of the electrodes includes a metallic current collector having a surface; b) associating at least one electrolyte, having at least one solvent, with the first and second electrodes; c) associating an additive with at least one of the electrolyte or the surface of the at least one metallic current collector; and d) forming a passivating layer between the surface of the metallic current collector and the electrolyte; wherein the step of forming the passivating layer includes the steps of: 1) charging the electrochemical cell; 2) substantially reducing the additive near the surface of the metallic current collector so that the reduced additive is substantially insoluble with the electrolyte; 3) substantially blocking the at least one solvent in the electrolyte from chemical interaction with the surface of the metallic current collector; and 4) substantially precluding gas formation within the electrochemical cell as a result of decomposition of the additive or reduced additive during cell cycling and storage.
REFERENCES:
patent: 5529859 (1996-06-01), Shu et al.
patent: 5626981 (1997-05-01), Simon et al.
patent: 7-220756 (1995-08-01), None
patent: 8-273700 (1996-10-01), None
Fauteux Denis G.
Kolb Eric S.
Van Buren Martin
Dove Tracy
Factor & Partners
Mitsubishi Chemical Corporation
Nuzzolillo Maria
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