Hybrid electric vehicle

Details Hybrid electric vehicle Hybrid electric vehicle

2001-12-10

2003-05-06

Vanaman, Frank Bennett (Department: 3618)

Motor vehicles

Power

Electric

Reexamination Certificate

active

06557655

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a hybrid electric vehicle incorporating an integrated propulsion system. More specifically, this integrated propulsion system comprises a combustion engine, an electric motor, high specific power, high energy density nickel-metal hydride (NiMH) batteries, and preferably a regenerative braking system. The NiMH batteries of the invention have negative electrodes with substrates of enhance current collecting capabilities, positive electrodes having enhance conductivity, and other improvements to enhance the power delivery capability of the battery and permit maximum operating efficiency during charge and discharge cycling while maintaining a combination of energy density and power density which provides enhanced performance beyond the capabilities of prior art NiMH battery systems.
BACKGROUND OF THE INVENTION
Advanced automotive battery development for vehicle propulsion has, in the past, been directed primarily at the requirement of fully electric propulsion systems for such vehicles. To this end, Stanford Ovshinsky and his battery development teams at Energy Conversion Devices, Inc. and Ovonic Battery Company have made great advances in nickel-metal hydride battery technology for such applications.
Initially effort focused on metal hydride alloys for forming the negative electrodes of such batteries. 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 highly disordered “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.
Disordered metal hydride alloys have a substantially increased density of catalytically active sites and storage sites compared to single or multi-phase compositionally homogeneous 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. More specifically, these alloys are tailored to allow bulk storage of the dissociated hydrogen atoms at bonding strengths within the range of reversibility suitable for use in secondary battery applications.
Some extremely efficient electrochemical hydrogen storage materials were formulated, based on the disordered materials described above. These are the Ti—V—Zr—Ni type active materials such as disclosed in U.S. Pat. No. 4,551,400 (“the '400 Patent”) to Sapru, Hong, Fetcenko, and Venkatesan, the disclosure of which is incorporated by reference. These materials reversibly form hydrides in order to store hydrogen. All the materials used in the '400 Patent utilize a generic Ti—V—Ni composition, where at least Ti, V, and Ni are present and may be modified with Cr, Zr, and Al. The materials of the '400 Patent are multiphase materials, which may contain, but are not limited to, one or more phases with C
14
and C
15
type crystal structures.
Other Ti—V—Zr—Ni alloys are also used for rechargeable hydrogen storage negative electrodes. One such family of materials are those described in U.S. Pat. No. 4,728,586 (“the '586 Patent”) to Venkatesan, Reichman, and Fetcenko, the disclosure of which is incorporated by reference. The '586 Patent describes a specific sub-class of these Ti—V—Ni—Zr alloys comprising Ti, V, Zr, Ni, and a fifth component, Cr. The '586 Patent, mentions the possibility of additives and modifiers beyond the Ti, V, Zr, Ni, and Cr components of the alloys, and generally discusses specific additives and modifiers, the amounts and interactions of these modifiers, and the particular benefits that could be expected from them.
In contrast to the Ovonic alloys described above, the older alloys were generally considered “ordered” materials that had different chemistry, microstructure, and electrochemical characteristics. The performance of the early ordered materials was poor, but 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 significantly. This is due as much to the disorder contributed by the modifiers as it is to their electrical and chemical properties. This evolution of alloys from a specific class of “ordered” materials to the current multi-component, multiphase “disordered” alloys is shown in the following patents: (i) U.S. Pat. No. 3,874,928; (ii) U.S. Pat. No. 4,214,043; (iii) U.S. Pat. No. 4,107,395; (iv) U.S. Pat. No. 4,107,405; (v) U.S. Pat. No. 4,112,199; (vi) U.S. Pat. No. 4,125,688 (vii) U.S. Pat. No. 4,214,043; (viii) U.S. Pat. No.4,216,274; (ix) U.S. Pat. No. 4,487,817; (x) U.S. Pat. No. 4,605,603; (xii) U.S. Pat. No. 4,696,873; and (xiii) U.S. Pat. No. 4,699,856. (These references are discussed extensively in U.S. Pat. No. 5,096,667 and this discussion is specifically incorporated by reference). Additional discussion is contained in the following U.S. patents, the contents of which are specifically incorporated by reference: U.S. Pat. Nos. 5,104,617; 5,238,756; 5,277,999; 5,407,761; 5,536,591; 5,506,069; and 5,554,456.
Ovshinsky and his teams next turned their attention to the positive electrode of the batteries. The positive electrodes today are typically pasted nickel electrodes, which consist of nickel hydroxide particles in contact with a conductive network or substrate, preferably having a high surface area. There have been several variants of these electrodes including the so-called plastic-bonded nickel electrodes which utilize graphite as a microconductor and also including the so-called foam-metal electrodes which utilize high porosity nickel foam as a substrate loaded with spherical nickel hydroxide particles and cobalt conductivity enhancing additives. Pasted electrodes of the foam-metal type have started to penetrate the consumer market due to their low cost and higher energy density relative to sintered nickel electrodes.
Conventionally, the nickel battery electrode reaction has been considered to be a one electron process involving oxidation of divalent nickel hydroxide to trivalent nickel oxyhydroxide on charge and subsequent discharge of trivalent nickel oxyhydroxide to divalent nickel hydroxide. However, quadrivalent nickel is also involved in the nickel hydroxide redox reaction, the utilization of which has never been investigated.
In practice, electrode capacity beyond the one-electron transfer theoretical capacity is not usually observed. One reason for this is incomplete utilization of the active material due to electronic isolation of oxidized material. Because reduced nickel hydroxide material has high electronic resistance, the reduction of nickel hydroxide adjacent the current collector forms a less conductive surface that interferes with the subsequent reduction of oxidized active material that is farther away.
Ovonic Battery Company has developed positive electrode materials that have demonstrated reliable transfer of more than one electron per nickel atom. Such stable, disordered positive electrode materials are described in U.S. Pat. Nos. 5,344,728; 5,348,822; 5,523,182; 5,569,563; and 5,567,599; the contents of which are specifically incorporated by reference.
As a result of this research into the negative and positive electrode active materials, the Ovonic Nickel Metal Hydride (NiMH) battery has reached an advanced stage of development for EVs. Ovonic electric vehicle batteries are capable of propelling an electric vehicle to over 370 miles (due to a specific energy of about 90 Wh/Kg), long cycle life (over

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