Electrochemical cells

Abstract

Electrochemical cells having an oxidizable active anode material, a solid cathode material, and an electrolytic solution between and in contact with the anode and the cathode, the electrolytic solution comprising a liquid covalent inorganic oxyhalide or thiohalide solvent and a solute dissolved therein, the inorganic oxyhalide or thiohalide solvent being the sole oxidant material and sole solvent material in the cell. In a first embodiment of the invention, the cathode comprises a solid, non-consumable, electrically conducting, inert current collector upon the surface of which the inorganic oxyhalide or thiohalide solvent is electrochemically reduced, whereby the inorganic oxyhalide or thiohalide solvent in conjunction with the oxidizable anode serves as a source of electrical energy during operation of the cell. In a second embodiment, the cathode is selected from sulfur and certain of the solid compounds of the Group VI A elements with metallic elements. Such cells have higher open circuit potentials than the open circuit potential calculated from the expected anode-cathode reactions. These higher potentials are attributed to the involvement of the solvent in the electrode reactions.

Parent Case Text

REFERENCE TO PARENT APPLICATION

This application is a continuation-in-part application of application Ser. No. 305,812, filed Nov. 13, 1972 now abandoned.

Description

BACKGROUND OF THE INVENTION

This invention relates to electrochemical cells. Most particularly, it relates to electrochemical cells having an oxidizable active anode material, a solid cathode material selected from a variety of materials, and a liquid covalent inorganic oxyhalide or thiohalide as the solvent for the electrolytic solution.

Modern technology has placed increased emphasis on producing an electrochemical power source having improved reliability, light weight, small size, high power and long life. Power sources meeting these requirements find ready civilian and military applications in portable communications systems, entertainment products, emergency lights, and portable electronic devices, such as wristwatches and hearing aids. An inexpensive, lightweight, high power, reliable power source would be of great value for use, for example, with portable radios or television sets.

Various high-voltage, high-energy density electrochemical cells have been the subject of recent investigation. Much of the work in this area has been involved with electrochemical cells having negative electrodes comprising highly reactive metals such as lithium.

Work on electrolytes for lithium-based electrochemical power sources has progressed generally along two major lines: high temperature, inorganic molten salt electrolytes and organic solvent-based electrolytes. A cell which utilizes a molten salt electrolyte provides a chemically stable system in which strong oxidants such as chlorine can be used as cathodes. For example, a molten salt cell utilizing a lithium anode and chlorine cathode provides exceptionally high energy and power density making development of a practical cell with these materials of particular interest. The molten salt lithium-chlorine cell (having a lithium anode, chlorine cathode and molten salt, typically lithium chloride, electrolyte) has many characteristics desirable in a high performance electrochemical cell. The anode is highly electropositive, and the cathode is highly electronegative. The equivalent weight of the reaction product is low and the anode, cathode and electrolyte conductivities are high. Nevertheless, these cells have severe problems. The temperature range of operation, which for the lithium chloride electrolyte is 450.degree.C to 650.degree.C, necessitates heating systems and insulation that increase cell cost, weight and complexity. To collect and store the chlorine evolved in rechargeable cells at these high temperatures, auxiliary systems are needed. In addition, there are few materials that can withstand, for extended periods of time, the attack of molten lithium, chlorine and molten lithium chloride at these temperatures; therefore, the operating lifetime of these cells is relatively short, typically 20 to 30 minutes. The measured and theoretical open circuit voltage of these high temperature cells is about 3.5 volts, although approximately 4 volts are theoretically obtainable at 25.degree.C (at higher temperatures the potential is lower because of the energy charge in the overall cell reaction).

In parallel with the development of lithium cells with molten salt electrolytes, lithium cells with nonhydroxylic organic solvents have been developed. These cells have been called "organic electrolyte cells" although typically they employ electrolytes consisting of inorganic salts in organic solvents. Cells of this type have the advantage of being operable at room temperature; however, chlorine itself and other strong oxidants cannot be used as the cathode depolarizer with these solvents since the solvents are oxidized by chlorine. Therefore, cells of this type will not provide an energy density as high as a lithium/chloride cell.

In application Ser. No. 385,375, filed Aug. 3, 1973, a continuation-in-part of application Ser. No. 212,725 filed Dec. 27, 1971, now abandoned, there are described electrochemical cells having an active anode material selected from a specific group of materials, including lithium, a cathode material selected from a specific group of materials, and an electrolytic solution containing phosphorus oxychloride as the solvent material and a solute, selected from a wide range of materials, dissolved in the phosphorus oxychloride.

The present invention relates to the invention described in the aforementioned application in that the same anodic, cathodic and solute materials can be utilized in the present invention; however, this invention relates to the use of such materials with different solvent materials.

SUMMARY OF THE INVENTION

This invention is directed to electrochemical cells having an oxidizable active anode material, a solid cathode material, and an electrolytic solution between and in contact with the anode and the cathode, the electrolytic solution comprising a liquid covalent inorganic oxyhalide or thiohalide solvent and a solute dissolved therein, the inorganic oxyhalide or thiohalide solvent being the sole oxidant material and sole solvent material in the cell.

In a first embodiment of the invention, the cathode comprises a solid, non-consumable, electrically conducting, inert current collector upon the surface of which the inorganic oxyhalide or thiohalide solvent is electrochemically reduced, whereby the inorganic oxyhalide or thiohalide solvent, in conjunction with the oxidizable anode, serves as a source of electrical energy during operation of the cell. Applicable cathode materials for this embodiment include certain electrically conducting metallic oxides, sulfides and selenides, such as cuprous oxide, titanium dioxide, uranium oxide (UO.sub.2), zinc oxide, tantalum oxide, cuprous sulfide, cupric sulfide, nickel sulfide, ferrous sulfide, cobalt sulfide, silver (I) sulfide, cadmium sulfide, lead sulfide, cuprous selenide, lead selenide, silver (I) selenide, cuprous telluride, silver (I) telluride, and lead telluride. Other applicable cathode materials including selenium; and non-stoichiometric chalcogenides such as FeS.sub.1.sub.-2, CoS.sub.1.sub.-2, CoTe.sub.1.sub.-2, CrS.sub..95.sub.-1.5, and UO.sub.1.5.sub.-3. It is believed that the inorganic oxyhalide or thiohalide solvent is electrochemically reduced on the surface of the cathode material to yield a halogen ion which reacts with a metallic ion from the anode to form a soluble metal halide, such as, for example, lithium chloride. The overall effect is to electrochemically reduce the solvent by removal of a portion of its halogen content and thereby obtain electrical energy therefrom. This energy can be attained, however, in the absence of other cathode depolarizers or oxidant materials, such as sulfur dioxide, which are not needed in the cells of this invention since the inorganic oxyhalide or thiohalide solvent also serves as the oxidant material. In addition, it is believed that the inorganic oxyhalide or thiohalide solvent passivates the anode material, whereby the need to provide an additive or a further material to passivate the anode is obviated.

The electrically conducting metallic discharge product of a metal chalcogenide (i.e., metal chalcogenide - metal) or an electrically conducting reduced form of a metal chalcogenide in a lower oxidation state than the material originally incorporated into the cell (i.e., Fe.sub.2 O.sub.3 - FeO; Ni.sub.2 S.sub.3 - NiS) are also suitable cathode materials. In this context, when this specification refers to the cathode material of this first embodiment it is intended to mean a solid, non-consumable, electrically conducting, inert current collector, and, as indicated above, such a material can be placed into the cell in that form or can be formed in situ, as by the reductions referred to above.

The anode is an oxidizable material and is preferably lithium metal. Other oxidizable anode materials contemplated for use in the cells of this invention include the other alkali metals, such as sodium, potassium, rubidium and cesium; the alkaline earth metals, such as beryllium, magnesium, calcium, strontium and barium; the Group III A metals, such as aluminum, gallium, indium, and thallium; the Group IV A metals, such as tin and lead; the Group V A metals, such as antimony and bismuth; the transition metals, such as scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold and mercury; and rare earth metals, such as lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Such anode materials are satisfactory if they provide a potential vs. the inert cathode current collector in the covalent inorganic oxyhalide-based or thiohalide-based electrolytic solution (i.e., the anode is more electropositive than the inert cathode current collector utilized) and the anode can be oxidized thereby. The anode may be constructed of the oxidizable material in contact with a metal grid. The grid for a lithium anode, for example, may be made of nickel, nickel alloys (such as monel), stainless steel, silver or platinum.

The total cathode structure may be formed by mixing the particular cathode material with a finely divided conductive material, such as carbon black or graphite fibers, or small metal particles, such as silver particles or nickel flake to render the mixture conductive. This is of particular interest with respect to the cathode materials of the second embodiment described below, such as pressed sulphur which preferably is made conductive by this technique. In addition, materials like polypropylene, polyethylene and polytetrafluoroethylene may be incorporated with the solid cathodic material to act as a binder.

As used throughout this specification and claims, when an electrochemical cell is designated to have a particular anode or cathode, or to have a particular anode or cathode material, that anode or cathode, or anode or cathode material, shall mean the electrochemically active component of the anode or cathode structure, or the non-consumable, electrically conducting, inert cathode current collector component in the case of the first embodiment of the invention. Such a component may be in contact with, or form a part of, a suitable substrate which further defines the total anode or cathode structure.

As indicated above, the electrolytic solution comprises a liquid covalent inorganic oxyhalide or thiohalide solvent and a solute dissolved therein. Applicable solvent materials include monofluorophosphoryl dichloride, monobromophosphoryl difluoride, monofluorophosphoryl dibromide, thiophosphoryl chloride, monofluorothiophosphoryl dichloride, thionyl chloride, thionyl bromide, sulfuryl chloride, monobromothiophosphoryl difluoride, monofluorothiophosphoryl dibromide, and mixtures thereof.

It is preferred that the solvent be dried prior to use. This is accomplished by boiling the solvent material with clean lithium shot for 12 hours at room temperature under an argon atmosphere. The solvent is then distilled at atmospheric pressure and the material which boils at or about the boiling point of the particular material being dried is collected. Other solvents can be dried in an analogous manner or by techniques known in the art. Since these solvents are, in the first embodiment of the invention, electrochemically reducible, but otherwise non-reactive, and the reaction products of such reduction are relatively non-reactive, cells can be constructed with a wide range of anode and cathode materials, particularly anode materials which themselves are highly reactive, such as, for example, lithium.

The typical solute provides at least one anion of the general formula X.sup.-, MX.sub.4.sup.-, M'X.sub.6.sup.-, and M"Cl.sub.6.sup.=, where M is an element selected from the group consisting of aluminum and boron; M' is an element selected from the group consisting of phosphorus, arsenic, and antimony; M" is an element selected from the group consisting of tin, zirconium and titanium; and X is a halogen. Examples of suitable solutes yielding anions MX.sub.4.sup.- are: tetrachloroaluminates (AlCl.sub.4.sup.-), tetrabromoaluminates (AlBr.sub.4.sup.-), tetrachloroborates (BCl.sub.4.sup.-), and tetrafluoroborates (BF.sub.4.sup.-). Examples of solutes yielding anoins M'X.sub.6.sup.- are: hexafluorophosphates (PF.sub.6.sup.-), hexafluoroarsenates (AsF.sub.6.sup.-), hexafluoroantimonates (SbF.sub.6.sup.-) and hexachloroantimonates (SbCl.sub.6.sup.-). Examples of solutes yielding anions (M"Cl.sub.6.sup.= are: hexachlorostannates (SnCl.sub.6.sup.=), hexachlorozirconates (ZrCl.sub.6.sup.=) and hexachlorotitanates (TiCl.sub.6.sup.=). Solutes yielding a halogen anion, particularly chlorides (Cl.sup.-), bromides (Br.sup.-), and iodides (I.sup.-), and solutes providing one of the anions dichloroiodates (ICl.sub. 2.sup.-), dichlorophosphates (PO.sub.2 Cl.sub.2.sup.-), perchlorates (ClO.sub.4.sup.-) and chlorosulfates (SO.sub.3 Cl.sup.-) are also contemplated within the scope of this invention.

The solute also provides at least one cation. This cation may be of an alkali metal, such as lithium, sodium, potassium, cesium, and rubidium; an alkaline earth metal, such as magnesium, calcium, strontium, and barium; or a lanthanide rare earth element, such as lanthanum, terbium, neodymium, cerium, europium and samarium. Cations having the following generaly formula R.sub.4 N.sup.+ where R is a radical selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl and isobutyl are also contemplated to be suitable for use in this invention. Examples of suitable cations are: tetramethylammonium (CH.sub.3).sub.4.sup.+, tetraethylammonium (C.sub.2 H.sub.5).sub.4 N.sup.+, tetrapropylammonium (C.sub.3 H.sub.7).sub.4 N.sup.+, and tetrabutylammonium (C.sub.4 H.sub.9).sub.4 N.sup.+. These cations may be added as the tetraalkylammonium chloride, for example. Other cations contemplated within the scope of this invention are those resulting from solvent dissociation, SOCl.sup.+ in the case of a thionyl chloride-based electrolytic solution, and SO.sub.2 Cl.sup.+, etc.

The solute for a particular cell can be chosen to yield a combination of any of the anions and cations listed above; however, the electrolyte must contain at least 10.sup.-.sup.3 moles per liter of cation and at least 10.sup.-.sup.3 moles per liter of anion. Preferably, at least 10.sup.-.sup.1 moles per liter of cation and at least 10.sup.-.sup.1 moles per liter of anion are present. It is also preferred that a dried solute be used.

Solutes having lithium cations and large anions which are stable to oxidation and reduction are particularly desirable. The preferred lithium solute compounds are: lithium tetrachloroaluminate, lithium tetrachloroborate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium hexachloroantimonate, lithium hexachlorostannate, lithium hexachlorozirconate, lithium hexachlorotitanate and lithium chlorosulfate. Other preferred compounds are Lewis acids, particularly aluminum chloride (AlCl.sub.3), boron fluoride (BF.sub.3), tin chloride (SnCl.sub.4), antimony chloride (SbCl.sub.5), antimony fluoride (SbF.sub.5), titanium chloride (TiCl.sub.4), aluminum bromide (AlBr.sub.3), phosphorus fluoride (PF.sub.5), phosphorus chloride (PCl.sub.5), arsenic fluoride (AsF.sub.5), arsenic chloride (AsCl.sub.5), zinc chloride (ZnCl.sub.2) and zirconium chloride (ZrCl.sub.4), in conjunction with a metal halide such as lithium chloride. In addition, Lewis bases having the general formula A.sub.m B.sub.n where A is an element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium and the rare earths and B is an element selected from fluorine, chlorine, bromine, iodine and oxygen are also useful. Included in this latter category are cesium chloride, rubidium chloride, and barium chloride.

The required anion and cation may be formed as a result of a chemical reaction directly with the solvent. For example, the Lewis acid AlCl.sub.3 will react with the solvent PSCl.sub.3 to yield the anion AlCl.sub.4.sup.-. The anion and cation may also be formed as a result of the reaction of a Lewis acid with a Lewis base dissolved in the solvent. For example, lithium chloride, LiCl, a Lewis base, will react with AlCl.sub.3 to form LiAlCl.sub.4 which dissociates in part to solvated Li.sup.+ and AlCl.sub.4.sup.-.

Although not required for all of the cells of this invention, a suitable separator can be employed to prevent the reaction of anode and cathode materials when no electrical current flows through the external circuit. A separator prevents the diffusion of cathode material to the anode. When the cathode material is soluble in the electrolyte, an ion selective separator which allows only a particular ion or group of ions to migrate between the anode and cathode may be used. Two major groups of ion selective separators are organic permselective membranes and inorganic zeolites. A particularly useful membrane which permits the flow of lithium ions is perfluorinated hydrocarbon (membrane) sulphonate. If the cathode material is not soluble in the electrolyte, or does not react spontaneously with the anode material, mechanical separators can be used. A wide variety of ceramic and plastic materials having small pore sizes are available. Examples of such materials include: alumina, beryllia, titania, porcelain, porous glass, fritted glass, nonwoven porous polytetrafluoroethylene and other fluorinated polymers, polypropylene and polyethylene.

In the second embodiment of the invention, the cathode comprises a solid, non-electrically conducting material selected from the group consisting of sulfur and certain of the solid compounds of the Group VI A elements with metallic elements. Excluded from this group of cathode materials are those cathode materials which would otherwise fall into this class but instead are included in the class of cathode materials applicable to the first embodiment of this invention. Cathode materials applicable to this embodiment include sulfur, mercuric sulfide, silver oxide, chromium trioxide, vanadium oxides, manganese oxide, lead oxides, nickel oxides, cupric oxide, niobium pentaoxide, molybdenum trioxide, bismuth trioxide, and mercuric oxide. The remaining components of the cells of this embodiment are as set forth above with respect to the cells of the first embodiment.

The cells of the second embodiment have open circuit potentials that are substantially higher than the open circuit potential calculated from the expected anode/cathode reactions using, for example, sulfur, metallic oxide, or metallic sulfide cathodes. This higher potential is attributed to the involvement of the inorganic oxyhalide or thiohalide solvent in the electrode reactions. Such involvement, however, is not believed to be by reduction of the solvent, as with the cells of the first embodiment of the invention; rather it is believed to involve a substitution-type transformation of the solvents with the phosphor, sulfur or selenium of the solvent remaining in its initial valence state. For example, cells of this embodiment with oxide cathodes utilizing sulfuryl chloride as the solvent might form disulfuryl chloride as one of the products of the cell reactions, the sulfur remaining in its initial valence state of six. Because of this involvement of the solvent in the cell reactions, the cells of this embodiment of the invention have initially higher energy densities than that previously obtainable with alkali metal anode cells.

As indicated above, the electrochemical cells of this invention exclude sulfur dioxide and other oxidants as cathode depolarizer materials or as solvent or cosolvent materials. Thus, the present invention describes cells in which the oxyhalide or thiohalide solvent is electrochemically reduced (first embodiment) or involved in the electrode reactions (second embodiment) in the absence of other oxidants, such as sulfur dioxide; thus distinguishing this invention from the cells of Maricle et al, U.S. Pat. No. 3,567,515 and U.S. Pat. No. 3,578,500, all of which make use of sulfur dioxide as an oxidant material. Further this invention describes the stability of lithium and the inorganic oxyhalide or thiohalide solvent, in the absence of the passivating film on the lithium caused by the sulfur dioxide of Maricle et al, supra. It is now believed that the oxyhalide or thiohalide solvent passivates the anode material, whereby the need to provide a further material, such as the sulfur dioxide of Maricle et al, supra, to perform such a function is eliminated.

The present invention is also considered distinct from the cells described in French Pat. Nos. 1,000,044; 1,583,804; and 2,079,744. The cells described therein make use of dissolved or in situ generated oxidants as the active cathode material (called the anode or positive electrode in the French patents). Thus, the first embodiment of this invention is distinguished because the solvent material is the sole oxidant material in the cell and the cathode is an inert current collector, and the second embodiment is distinguished because the cathode materials thereof are different from the specifically identified dissolved salts of French Pat. No. 1,000,044, and the halogens of French Pat. Nos. 1,583,804 and 2,079,744.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The following Examples are given to enable those skilled in the art to more clearly understand and practice the present invention. They should not be considered as a limitation of the scope of the invention but merely as being illustrative and representative thereof.

In the following Examples, unless otherwise indicated, the electrochemical cell utilized in these Examples is of the following configuration:

The cathodes are constructed by pressing a blend of active cathode material and sufficient binder, generally polytetrafluoroethylene or polyethylene, onto an expanded copper or nickel screen in a heated square die 3.75 cm on each side at 2000 psig for 3 minutes. The cathode is then heat sealed in a nonwoven polypropylene envelope and dried in a vacuum oven before being transferred to an argon glove box for assembly into a cell. The anodes are constructed in the argon glove box by pressing expanded nickel screen onto 0.038 cm or 0.056 cm thick lithium foil. The anode is folded to envelope the cathode on both sides. The surface between the electrodes in these cells is 28 cm.sup.2. The electrodes are placed in polyethylene or polytetrafluoroethylene rectangular cases of various sizes and adapted to contain from 8 to 25 ml. of electrolyte. Electrical properties of the cells are obtained with the cells in the argon glove box since the cells are not sealed, but only covered with a tight fitting cap.

Unless otherwise noted, the cells are discharged at 1 mA/cm.sup.2 (28 mA), and energy density data, when given, excludes the weight of the case.

EXAMPLE I

The cathode material is a blend of 82% S, 5% AgS, 10% graphite and 3% carbon black. The anode is lithium, and the electrolyte is 1.8 M LiAlCl.sub.4 in SOCl.sub.2. Open circuit potential is 3.54 volts, which decreases to 3.13 volts upon discharge of 25 mA (i.e., 1 mA/cm.sup.2). Discharge lasts for 37.3 hours.

EXAMPLE II

An electrochemical cell is constructed having a lithium anode, a cathode having cupric sulfide as the active cathode component, and an electrolyte comprising a solution of lithium tetrafluoroborate in thiophosphoryl chloride.

EXAMPLE III

Example II is repeated except monofluorophosphoryl dichloride is substituted for the thiophosphoryl chloride.

EXAMPLE IV

Example II is repeated except a 1:1 (by weight) mixture of thionyl chloride and sulfuryl chloride is substituted for the thiophosphoryl chloride.

EXAMPLE V

Example II is repeated except a 1:1 (by weight) mixture of thionyl chloride and thiophosphoryl chloride is substituted for the thiophosphoryl chloride.

EXAMPLE VI

Example II is repeated except a 1:1 (by weight) mixture of sulfuryl chloride and monofluorophosphoryl dichloride is substituted for the thiophosphoryl chloride.

EXAMPLE VII

Example II is repeated except a 1:1 (by weight) mixture of thiophosphoryl chloride and monofluorophosphoryl dichloride is substituted for the thiophosphoryl chloride.

EXAMPLE VIII

Example II is repeated except monobromophosphoryl difluoride is substituted for the thiophosphoryl chloride.

EXAMPLE IX

Example II is repeated except monofluorophosphoryl dibromide is substituted for the thiophosphoryl chloride.

EXAMPLE X

Example II is repeated except monobromothiophosphoryl difluoride is substituted for the thiophosphoryl chloride.

EXAMPLE XI

Example II is repeated except thionyl chloride is substituted for the thiophosphoryl chloride.

EXAMPLE XII

Example II is repeated except thionyl bromide is substituted for the thiophosphoryl chloride.

EXAMPLE XIII

Example II is repeated except sulfuryl chloride is substituted for the thiophosphoryl chloride.

EXAMPLE XIV

Example II is repeated except monofluorothiophosphoryl dibromide is substituted for the thiophosphoryl chloride.

EXAMPLES XV - XXIX

In the following Examples, the cells have a lithium anode, and an electrolytic solution comprising a 1.8 M solution of lithium tetrachloroaluminate in thionyl chloride. The cathode component of each cell, the open circuit potential at 25.degree.C, and the current density at 50% polarization at 25.degree.C obtainable therewith are given in Table I below.

TABLE I ______________________________________ EX- CATHODE OPEN CIRCUIT CURRENT DENSITY AMPLE POTENTIAL, AT 50% POLARI- VOLTS ZATION (mA/cm.sup.2) ______________________________________ XV Nickel 3.66 1.142 XVI Gold 3.72 >8.000 XVII Tungsten 3.67 1.067 XVIII Palladium 3.74 1.225 XIX Molybdenum 3.69 1.573 XX Germanium 3.44 0.939 XXI Silicon 2.92 0.215 XXII Cobalt 3.56 0.644 XXIII Silver 2.91 1.835 XXIV 304 Stainless 3.56 0.221 Steel XXV Niobium 3.53 0.370 XXVI Manganese 3.58 2.082 XXVII Tantalum 3.44 0.497 XXVIII Titanium 3.06 1.201 XXIX Platinum 3.66 1.017 ______________________________________

EXAMPLE XXX

A lithium metal anode is operated against a nickel cathode in a two molar solution of lithium tetrachloroaluminate in sulfuryl chloride. The cell exhibits an open circuit potential of about 3.9 volts.

EXAMPLE XXXI

A pressed nickel oxide cathode comprised of 40% nickel oxide, 40% nickel powder and 20% Teflon on a nickel screen is operated against a lithium anode in the solution of Example XXX. The cell exhibits an open circuit potential of about 3.9 volts.

EXAMPLE XXXII

The cell of Example XXXI is operated with nickel sulfide replacing the nickel oxide. The cell exhibits an open circuit potential of about 3 volts.

EXAMPLE XXXIII

The cell of Example XXXII is operated in a one molar solution of lithium tetrachloroaluminate in monofluorophosphoryl dichloride at about 3.3 volts open circuit voltage.

EXAMPLE XXXIV

The cell of Example XXXI is operated in a saturated solution of lithium tetrachloroaluminate in an equal volume mixture of monobromophosphoryl difluoride and monofluorophosphoryl dichloride. The cell exhibits an open circuit potential of about 3 volts.

EXAMPLE XXXV

The cell of Example XXXII is operated in a saturated solution of lithium tetrachloroaluminate in a mixture composed of equal parts by volume of monofluorophosphoryl dichloride, monofluorothiophosphoryl dichloride and monobromothiophosphoryl difluoride. The cell exhibits an open circuit potential of about 3 volts.

While the present invention has been described with reference to specific embodiments thereof, it should be understood by those skilled in this art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, or composition of matter, process, process step or steps, or then-present objective to the spirit of this invention without departing from its essential teachings.

Claims

What is claimed is:

1. An electrochemical cell comprising an oxidizable active anode material; a solid, non-consumable, electrically conducting, inert cathode current collector; and an electrolytic solution between and in contact with said anode and said cathode current collector, said electrolytic solution consisting essentially of a liquid, electrochemically reducible, covalent inorganic oxyhalide or thiohalide solvent and a solute dissolved therein, said inorganic oxyhalide or thiohalide solvent being selected from the group consisting of monofluorophosphoryl dichloride, monobromophosphoryl difluoride, monofluorophosphoryl dibromide, thiophosphoryl chloride, monofluorothiophosphoryl dichloride, thionyl chloride, thionyl bromide, sulfuryl chloride, monobromothiophosphoryl difluoride, monofluorothiophosphoryl dibromide, and mixtures thereof; said inorganic oxyhalide or thiohalide solvent being the sole oxidant material and sole solvent material in said cell; said inorganic oxyhalide or thiohalide solvent being electrochemically reduced upon the surface of said cathode current collector, whereby said inorganic oxyhalide or thiohalide solvent in conjunction with said oxidizable anode material serves as a source of electrical energy during operation of said cell.

2. The electrochemical cell of claim 1 wherein said active anode material is selected from the group consisting of lithium, sodium, potassium, scandium, yttrium, lanthanum, and the lanthanide rare earth elements.

3. The electrochemical cell of claim 1 wherein said active anode material is lithium.

4. The electrochemical cell of claim 1 wherein said active anode material is sodium.

5. The electrochemical cell of claim 1 wherein said cathode current collector is cupric sulfide or nickel sulfide.

6. The electrochemical cell of claim 1 wherein said cathode current collector is selenium.

7. The electrochemical cell of claim 1 wherein said cathode current collector is a metallic selenide.

8. The electrochemical cell of claim 1 wherein said inorganic solvent is thionyl chloride.

9. The electrochemical cell of claim 1 wherein said inorganic solvent is sulfuryl chloride.

10. The electrochemical cell of claim 1 wherein said inorganic solvent is a mixture of thionyl chloride and sulfuryl chloride.

11. The electrochemical cell of claim 1 wherein said solute provides at least one anion having the formula X.sup.-, MX.sub.4.sup.-, M'X.sub.6.sup.-, and M"Cl.sub.6.sup.=, where M is an element selected from the group consisting of aluminum and boron; M' is an element selected from the group consisting of phosphorus, arsenic and antimony; M" is an element selected from the group consisting of tin, zirconium and titanium; and X is a halogen; said solute further providing at least one cation selected from the group consisting of alkali metals, the alkaline earth metals, the lanthanides, POCl.sub.2.sup.+, SOCl.sup.+, and R.sub.4 N.sup.+, where R is a radical selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl and isobutyl.

12. The electrochemical cell of claim 1 wherein said solute includes at least one compound selected from the group consisting of lithium tetrachloroaluminate, lithium tetrachloroborate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium hexachloroantimonate, lithium hexachlorostannate, lithium hexachlorozirconate, lithium hexachlorotitanate and lithium chlorosulfate.

13. The electrochemical cell of claim 1 wherein said solute includes a Lewis acid.

14. The electrochemical cell of claim 1 wherein said solute includes a Lewis base having the general formula A.sub.m B.sub.n, where A is an element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, and the rare earth elements; B is an element selected from the group consisting of fluorine, chlorine, bromine, iodine and oxygen; and m and n are integers.

15. The electrochemical cell of claim 1 wherein said solute includes a material providing an anion selected from the group consisting of dichloroiodates, dichlorophosphates, perchlorates, chlorosulfates, and adducts of dichlorophosphates with Lewis acids.

16. The electrochemical cell of claim 1 wherein one of the products of the discharge of said cell is the halide of said anode material, the halogen in said halide originating from said inorganic oxyhalide or thiohalide solvent.

17. The electrochemical cell of claim 1 wherein said cathode current collector material is formed in situ during discharge of said cell.

18. An electrochemical cell comprising an oxidizable active anode material; a solid active cathode material selected from the group consisting of sulfur and the non-electrically conducting compounds of the Group VI A elements with metallic elements; and an electrolytic solution between and in contact with said anode and said cathode, said electrolytic solution consisting essentially of a liquid inorganic oxyhalide or thiohalide solvent and a solute dissolved therein, said inorganic oxyhalide or thiohalide solvent being selected from the group consisting of monofluorophosphoryl dichloride, monobromophosphoryl difluoride, monofluorophosphoryl dibromide, thiophosphoryl chloride, monofluorothiophosphoryl dichloride, thionyl chloride, thionyl bromide, sulfuryl chloride, monobromothiophosphoryl difluoride, monofluorothiophosphoryl dibromide, and mixtures thereof; said inorganic oxyhalide or thiohalide solvent being the sole solvent material in said cell; said cell being free of other cathode depolarizers or oxidant materials; said cell exhibiting a higher open circuit potential than the open circuit potential calculated from the expected anode/cathode reactions.

19. The electrochemical cell of claim 18 wherein said anode material is lithium.

20. The electrochemical cell of claim 18 wherein said cathode material is sulfur.

21. The electrochemical cell of claim 18 wherein said cathode material is selected from the group consisting of the oxides, sulfides, selenides, and tellurides of metallic elements.

22. The electrochemical cell of claim 18 wherein said inorganic solvent is thionyl chloride.

23. The electrochemical cell of claim 18 wherein said inorganic solvent is sulfuryl chloride.

24. The electrochemical cell of claim 18 wherein said inorganic solvent is a mixture of thionyl chloride and sulfuryl chloride.