Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Flat-type unit cell and specific unit cell components
Utility Patent
1999-04-02
2001-01-02
Nuzzolillo, Maria (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Flat-type unit cell and specific unit cell components
C429S127000, C429S124000, C429S163000, C429S129000, C429S130000, C429S231950, C429S104000, C429S246000
Utility Patent
active
06168884
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the field of batteries. More particularly, the invention relates to a rechargeable thin-film battery that produces a lithium anode via plating onto the anode current collector during initial use (activation) of the battery.
2. Discussion of the Related Art
The capacities of rechargeable lithium-ion batteries are presently limited by the positive cathode, which serves as the lithium source during the initial charge. The reason for the limitation lies in the significantly smaller reversible capacity of the cathode material, such as LiCoO
2
(140 milli-ampere-hour per gram (mAh/g)), LiNiO
2
(190 mAh/g), LiMn
2
O
4
(110 mAh/g), or LiMnO
2
(180 mAh/g), compared to the “best” anode materials such as carbons and tin oxide and its derivatives. These anodes, in particular the tin oxide based materials, have the unfortunate characteristic of consuming a significant amount of lithium during the initial charge of the lithium-ion (Li-ion) battery. For an optimal battery system, the irreversible charge/discharge capacity loss of a selected anode material should be as small as possible in order to utilize as much of the cathode as possible.
Although considered the best anode material for thin-film batteries as far as electrochemical performance and the minimal initial capacity loss are concerned, the lithium metal anode has two major drawbacks. First, the deposition of lithium metal complicates the fabrication process of the battery and the as-fabricated air-sensitive lithium battery needs special packaging for shipping and handling. Second, due to the low melting point of lithium (181° C.), such a lithium battery is practically limited to about 100° C. and does not survive the temperatures of about 250° C. associated with the solder re-flow process, which is commonly used to assemble integrated circuits.
SUMMARY OF THE INVENTION
To avoid the inherent capacity loss of lithium-ion (Li-ion) batteries and circumvent the fabrication of a lithium metal anode, it is highly desirable to prepare a lithium battery precursor with “no” anode at all. To this end a lithium metal anode can be formed in-situ during the initial charge by plating lithium on an anode current collector, which does not form inter-metallic compounds with lithium. The anode current collector is sandwiched between a solid state electrolyte and an overlying layer.
A first aspect of the invention is implemented in an embodiment that is based on a thin-film rechargeable battery comprising a cathode film including a lithium transition metal oxide; an electrolyte film coupled to the cathode film; the electrolyte film being substantially nonreactive with oxidizing materials and with metallic lithium, an anode current collector coupled to the electrolyte film; and an overlying layer coupled to the anode current collector, wherein the thin-film rechargeable battery is activated during a charge by electrochemical plating of a metallic lithium anode between the anode current collector and the electrolyte film.
A second aspect of the invention is implemented in an embodiment that is based on method for forming a thin-film battery comprising providing a substrate, depositing a cathode current collector on the substrate, depositing a cathode film on the cathode current collector where the cathode film includes a lithium transition metal oxide, depositing an electrolyte film on the cathode film, depositing an anode current collector on the electrolyte film, and depositing an overlying layer on the anode current collector.
The term coupled, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. The term substantially, as used herein, is defined as approximately (e.g., preferably within 10% of, more preferably within 1% of, most preferably within 0.1% of).
These, and other, goals and aspects of the invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the invention and numerous specific details thereof, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the invention without departing from the spirit thereof, and the invention includes all such modifications.
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Bates John B.
Dudney Nancy J.
Neudecker Bernd J.
Lockheed Martin Energy Research Corporation
Martin Angela J.
Nuzzolillo Maria
Wilson Sonsini Goodrich & Rosati
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