Chemistry: electrical current producing apparatus – product – and – Fluid active material or two-fluid electrolyte combination... – Active material in molten state
Patent
1994-12-05
1996-07-16
Skapars, Anthony
Chemistry: electrical current producing apparatus, product, and
Fluid active material or two-fluid electrolyte combination...
Active material in molten state
429 50, 429104, 429112, 429218, H01M 436, H01M 1039
Patent
active
055365930
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an electrochemical cell and to methods of fabricating the cell and improving its capacity and/or power and capability of operating at low temperatures. The invention also relates to a new positive electrode or cathode during discharge for electrochemical cells and method of fabricating same, and more particularly, relates to electrochemical cells and positive electrodes for metal chloride batteries having lower internal impedance and greater discharge capacity with a higher specific energy and power.
According to the invention, an electrochemical cell comprises an alkali metal, and preferably, a sodium negative electrode or anode during discharge which is molten at operating temperatures of the cell, an alkali and preferably, a Na.sup.+ ion conducting solid electrolyte/separator, a molten salt liquid electrolyte in the positive electrode compartment which is compatible with the positive electrode, and which is also at least partially molten at the operating temperature of the cell, and a positive electrode which is impregnated by the liquid electrolyte and which comprises, as the electrochemically active positive electrode substance of the cell, a transition metal chloride which preferably is selected from the group consisting or iron chloride, nickel chloride, chromium chloride, cobalt chloride and manganese chloride or mixtures thereof. Since the cell with a Na electrode has received the major development effort, a shorthand method of referring to these cells is (Na/MCl.sub.2) battery or electrochemical cell, wherein M is one of the transition metals identified above. Batteries of this type are disclosed in U.S. Pat. No. 4,288,506 issued Sep. 8, 1981, to Coetzer et al. and U.S. Pat. No. 4,546,055 issued Oct. 8, 1985 to Coetzer et al. and U.S. Pat. No. 4,592,969 issued Jun. 3, 1986 to Coetzer et al. The batteries or electrochemical devices of the type herein discussed are useful as a power source alternative to petroleum engines and are being developed commercially, not only for electrically powered vehicles, but also for load leveling in electrical utilities.
An ideal electrochemical cell or battery should exhibit a number of characteristics, including low resistance and high discharge rates, operation over a wide temperature range, a capability to operate over a large number of cycles, and high energy on a volume, weight and cell basis. Generally, these types of electrochemical cells or batteries consist of two dissimilar metals in an ionically conductive medium, with the ionization potential of one metal sufficiently higher than the other metal to yield a voltage upon reduction/oxidation redox (coupling) over and above that needed to break down the electrolyte continuously at the positive electrode.
Metal typically goes into solution at the negative electrode or anode, releasing electrons to travel in the external circuit to the positive electrode, or cathode, doing work in transit. Material which will go through a valency drop on electrochemical discharge is included in the positive electrode. In essence, this material, the oxidizer, accepts electrons coming from the negative electrode and serves as the depolarizer. The depolarizer or cathode is positioned, in one embodiment, in the positive electrode in combination with some electrolyte-containing matrix, and should be porous to allow access of the electrolyte to the enlarged area of the depolarizer or cathode. Porosity of the cathode provides a surface at which the redox reaction may take place.
The economic and social advantages of powering automobiles from batteries are considerable as the vehicles could operate at relatively high efficiencies, such as 30-40%, and be non-polluting. Two important characteristics are considered in seeking an energy storage system for a vehicle. One of the characteristics or variables, specific power, designed in watt per kilogram (W/kg), determines to a large extent, acceleration and speed capabilities. The other consideration or variable of specific energy is designated as watt hours per k
REFERENCES:
patent: 4288506 (1981-09-01), Coetzer et al.
patent: 4546055 (1985-10-01), Coetzer et al.
patent: 4592969 (1986-08-01), Coetzer et al.
patent: 4910105 (1990-03-01), Tilley et al.
patent: 4973534 (1990-11-01), Adendorff et al.
Prakash Jai
Redey Laszlo I.
Vissers Donald R.
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