Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1998-12-02
2002-07-02
Brouillette, Gabrielle (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C420S900000
Reexamination Certificate
active
06413670
ABSTRACT:
FIELD OF THE INVENTION
The instant invention relates generally to nickel-metal hydride batteries and more specifically to high power nickel-metal hydride batteries. The batteries include negative electrodes which employ electrochemical hydrogen storage alloys with enhanced high discharge rate capacities, thereby increasing the specific power and high rate capabilities of the batteries. The negative electrode electrochemical hydrogen storage alloys include means to dramatically alter the discharge capacity thereof. As will be discussed hereinbelow in the Detailed Description of the Invention, these means include tailoring the local chemical and structural order of the materials by adding transition metals having d orbitals. This alteration results in discharge capacity curves for non-misch metal hydrogen storage alloys which are provide high capacity even at high discharge rates. Because the instant batteries can provide both high energy density and high power, they are uniquely suited for application in new uses and areas to which batteries were previously not apropos. A specific example of such means is Pd which increases the electrochemical hydrogen storage capacity at high discharge rates of high capacity non-misch metal alloys (misch metal alloys have inherently low hydrogen storage capacity.) These alloys have great advantages over prior art alloys which makes them particularly useful for electric vehicles, hybrid electric vehicles and have great utility for power tools and other high drain rate applications even ultracapacitors.
BACKGROUND OF THE INVENTION
Presently batteries which can deliver high power and yet be small and light weight (i.e. have a high specific power) are in high demand. These types of batteries are useful in applications such as electric vehicle and hybrid electric vehicle propulsion for which lack of range has been a serious limitation. Also, in the electric vehicle industry, the high power capabilities allow for utilization of regenerative breaking to replenish the charge of the batteries. These high power batteries are also useful for other high drain rate applications such as power tools, as starter batteries for internal combustion engines and, because of the high conductivity of the metallic negative electrodes, as a replacement for power sources such as ultracapacitors.
Advanced automotive battery development for vehicle propulsion has, in the past, been directed primarily at the requirement of a true electric vehicle. Utilizing Ovshinsky's principles of disorder, local order, and chemical modification, the hallmark Energy Conversion Devices, Inc. (“ECD”), battery development teams at ECD and Ovonic Battery Company (“OBC”) have made great advances in nickel-metal hydride battery technology.
Initially Ovshinsky and his teams focused on metal hydride alloys that form the negative electrode. As a result of their efforts, they were able to greatly increase the reversible hydrogen storage characteristics required for efficient and economical battery applications, and produce batteries capable of high density energy storage, efficient reversibility, high electrical efficiency, efficient bulk hydrogen storage without structural changes or poisoning, long cycle life, and repeated deep discharge. The improved characteristics of these “Ovonic” alloys, as they are now called, results from tailoring the local chemical order and hence the local structural order by the incorporation of selected modifier elements into a host matrix, as well as the use of non-equilibrium processing. Disordered metal hydride alloys have a substantially increased density of catalytically active sites and storage sites compared to single or ordered multi-phase crystalline materials. These additional sites are responsible for improved efficiency of electrochemical charging/discharging and an increase in electrical energy storage capacity. The nature and number of storage sites can even be designed independently of the catalytically active sites which can themselves be increased no only by individual atoms but also by topology and chemistry. More specifically, these alloys are tailored to allow bulk storage of the dissociated hydrogen atoms at binding strengths within the range of reversibility suitable for use in secondary battery applications. A complete description of the role of disorder in electrochemical alloys is found in U.S. Pat. No. 4,623,597, the disclosure of which is incorporated herein by reference.
Some extremely efficient electrochemical hydrogen storage materials were formulated, based on the disordered materials described above. These materials reversibly form hydrides in order to store hydrogen. The materials are multiphase materials, which may contain, but are not limited to, one or more phases with C
14
and C
15
type crystal structures.
In contrast to the Ovonic alloys, the older alloys were “ordered” materials that had homogeneous chemistry, a uniform microstructure, and generally poor electrochemical characteristics. In the early 1980's, as the degree of modification increased (that is as the number and amount of elemental modifiers increased), their performance began to improve. Unbeknownst to the artisans of that era, who did all that was possible to keep the electrode materials uniform, the improvement in electrochemical performance was due as much to the compositional disorder contributed by the modifiers as it was to the electrical and chemical properties of the electrode alloys.
Simply stated, in all metal-hydride alloys, as the degree of modification increases, the role of the initially ordered base alloy is of minor importance compared to the properties and disorder attributable to the particular modifiers. In addition, analysis of the present multiple component alloys available on the market and produced by a variety of manufactures indicates that these alloys are modified following the guidelines established for Ovonic alloy systems. Thus, as stated above, all highly modified alloys are disordered materials characterized by multiple components and multiple phases, i.e. Ovonic alloys.
As a result of this development of the negative electrode active materials, the Ovonic Nickel Metal Hydride (Ni—MH) battery has reached an advanced stage of development for EVs. Ovshinsky's teams have been able to produce electric vehicle batteries which are capable of propelling an electric vehicle to over 350 miles on a single charge (Tour d' Sol 1996). The Ovonic Ni—MH battery has demonstrated excellent energy density (up to about 90 Wh/Kg), long cycle life (over 1000 cycles at 80% DOD), abuse tolerance, and rapid recharge capability (up to 60% in 15 minutes). Additionally, the Ovonic battery has demonstrated higher power density than any other battery technology under test and evaluation for use as an EV stored energy source.
While Ovshinsky and his teams have made great advances in batteries for true electric vehicles, the Partnership for a New Generation of Vehicles (PNGV), a U.S. government-auto industry partnership initiated in 1996, has suggested that hybrid-electric vehicles (HEV's) could be the leading candidate to meet their goals of tripling auto fuel economy in the next decade. To realize this goal, lightweight, compact, high-power batteries would be required.
The use of a hybrid drive system offers critical advantages for both fuel economy and ultra-low emissions. Fuel engines achieve maximum efficiency when operating at constant rpm. Therefore, peak fuel efficiency can be achieved by employing a constant rpm fuel engine to provide energy to a high-power energy storage system that supplies peak power for acceleration and also recaptures kinetic energy through the use of regenerative braking.
Similarly, the ability to use a small engine operating at maximum efficiency and coupled with a pulse power energy storage system offers the best design for minimizing emissions associated with the use of a fuel engine. Therefore, a key enabling technology for HEV's is an energy storage system capable of providing very high pulse powe
Ovshinsky Stanford R.
Young Rosa
Brouillette Gabrielle
Ovonic Battery Company Inc.
Schumaker David W.
Siskind Marvin S.
Wills M.
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