Chemistry: electrical current producing apparatus – product – and – Deferred action type
Reexamination Certificate
1999-07-28
2001-04-24
Weiner, Laura (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Deferred action type
C429S300000, C429S302000, C429S303000
Reexamination Certificate
active
06221525
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 a dopant associated with an electrolyte. The dopant, among other things, controllably releases salt into the electrolyte, substantially precludes dendrite formation within the cell, controllably regulates internal pressure of the cell, and increases mechanical integrity of the electrolyte.
2. Background Art
Lithium based electrochemical cells have been known in the art for several years. Furthermore, lithium based electrochemical cells having liquid, gel, and/or polymeric electrolytes are likewise well known. While cells utilizing such electrolytes have exhibited some promising electrochemical performance characteristics, numerous deficiencies and/or problems associated with conventional electrolytes nevertheless persist. For example, dendrites can form near the electrode/electrolyte interface, which, over time, shorts the cell thereby rendering it inoperable. In addition, during cell operation, conventional electrolytes become polarized due to depletion of salts within the electrolyte. Unfortunately, conventional electrolyte systems do not have an internal mechanism for re-supplying salt once it has been depleted within the cell. Furthermore, the performance of an electrochemical cell depends greatly upon its internal setup. Specifically, to ensure proper electrode contact, the cell must maintain a certain internal pressure to keep, for example, the electrode active material in proper contact with the current collector. Conventional electrolytes do not provide an internal mechanism for regulating the internal pressures of the cell. Moreover, conventional liquid and gel electrolytes generally have low viscosities, thereby making them difficult to coat onto an electrode without deformation prior to curing.
It is therefore an object of the present invention to provide an electrochemical cell having an electrolyte doped with an agent to remedy, among other things, the aforementioned short comings associated with conventional electrolytes.
SUMMARY OF THE INVENTION
The present invention is directed to an electrochemical cell comprising: (a) a first electrode and a second electrode; (b) an electrolyte; and (c) a dopant associated with the electrolyte, wherein the dopant comprises a reservoir for controllably releasing salt into the electrolyte.
In a preferred embodiment of the invention, the electrochemical cell further comprises means for controllably regulating internal pressure of the electrochemical cell. In this embodiment the pressure regulating means comprises the dopant.
In another preferred embodiment of the invention, the electrochemical cell further comprises means for substantially precluding dendrite formation within the cell. In this embodiment the dendrite preclusion means comprises the dopant.
The present invention is also directed to an electrochemical cell comprising: (a) a first electrode and a second electrode; (b) an electrolyte; and (c) a dopant associated with the electrolyte, wherein the dopant comprises means for controllably regulating internal pressure of the electrochemical cell.
In a preferred embodiment of the invention, the electrochemical cell further comprises means for controllably releasing salt into the electrolyte. In this embodiment the salt releasing means comprises the dopant.
In another preferred embodiment of the invention, the electrochemical cell further comprises means for substantially precluding dendrite formation within the cell. In this embodiment, the dendrite preclusion means comprises the dopant.
The present invention is further directed to an electrochemical cell comprising: (a) a first electrode and a second electrode; (b) an electrolyte; and (c) a dopant associated with the electrolyte, wherein the dopant comprises at least one of: (1) a reservoir for controllably releasing salt into the electrolyte; (2) means for controllably regulating internal pressure of the electrochemical cell; and (3) means for substantially precluding dendrite formation within the cell.
In yet another preferred embodiment of the invention, the dopant is selected from at least one of the group consisting essentially of poly(methyl methacrylate), lithium polysilicate, and mixtures thereof.
Preferably, the reservoir of the dopant may contain a salt selected from at least one of the group consisting essentially of LiAsF
6
, LiPF
6
, LiCF
3
SO
3
, LiN(CF
3
SO
2
)
3
, LiBF
4
, LiClO
4
, and mixtures thereof
The concentration of the dopant may range from approximately 0.5% to approximately 50% by weight of the electrolyte and preferably ranges from approximately 2% to approximately 25% by weight of the electrolyte.
In a preferred embodiment of the invention, the molecular weight of the poly(methyl methacrylate) ranges from approximately 750,000 to approximately 1,000,000.
The present invention is additionally directed to an electrochemical cell comprising: (a) a first electrode and a second electrode; (b) an electrolyte; and (c) means for maintaining conductivity of the electrolyte in the present of a dopant. In this embodiment the conductivity maintaining means comprises the dopant comprising lithium polysilicate.
The present invention further provides a process for fabricating an electrochemical cell comprising the steps of: (a) fabricating a first electrode and a second electrode; (b) associating a dopant with an electrolyte, wherein the dopant comprises a reservoir for controllably releasing salt into the electrolyte; (c) controllably applying the electrolyte to at least a portion of the first electrode; (d) associating a second electrode with the electrolyte; and (e) at least partially curing the electrolyte.
The present invention is also directed to an electrochemical process within an electrochemical cell comprising the steps of: (a) cycling an electrochemical cell having a first electrode, a second electrode, an electrolyte comprising a salt, and a dopant associated with the electrolyte; (b) consuming a portion of salt within the electrolyte; and (c) controllably releasing a salt from the dopant into the electrolyte.
In a preferred embodiment of the invention, the process, further comprises the step of controllably regulating the internal pressure of the electrochemical cell and/or substantially precluding dendrite formation within the electrochemical cell.
REFERENCES:
patent: 4556614 (1985-12-01), le Mehaute et al.
patent: 4654279 (1987-03-01), Bauer et al.
patent: 4818643 (1989-04-01), Cook et al.
patent: 4888257 (1989-12-01), Narang
patent: 5853917 (1998-12-01), Fauteux et al.
Fauteux Denis G.
Kolb Eric S.
Factor & Partners
Mitsubishi Chemical Corporation
Weiner Laura
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