WO2001035475A1

WO2001035475A1 - Lithium primary batteries

Info

Publication number: WO2001035475A1
Application number: PCT/US2000/030911
Authority: WO
Inventors: Yuriy V. Mikhaylik; Terje A. Skotheim; Charles A. Angell
Original assignee: Moltech Corporation
Priority date: 1999-11-12
Filing date: 2000-11-10
Publication date: 2001-05-17
Also published as: AU1595401A

Abstract

Provided is a lithium primary battery in which the cathode comprises an electroactive sulfur-containing material and the electrolyte comprises one or more non-aqueous solvents and one or more voltage-enhancing reactive components, wherein the reactive components are non-electroactive but enhance the voltage of the lithium primary battery. Suitable voltage-enhancing reactive components include organic halides, inorganic halides, and phosphorus chalcogenides. Also are provided methods for making the lithium primary battery.

Description

LITHIUM PRIMARY BATTERIES

TECHNICAL FIELD

The present invention relates generally to the field of electrochemical cells. More particularly, this invention pertains to lithium primary batteries in which the cathode comprises an electroactive sulfur-containing material and the electrolyte comprises a reactive component that enhances the voltage ofthe lithium primary battery.

BACKGROUND

Throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent specifications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state ofthe art to which this invention pertains.

As the evolution of batteries continues, and particularly as lithium batteries become more widely accepted for a variety of uses, the need for safe, long lasting high energy batteries becomes more important. There has been considerable interest in recent years in developing high energy density cathode-active materials for use in high energy primary and secondary batteries with lithium containing anodes. Various types of cathode materials for the manufacture of lithium batteries are known in the art.

One class of lithium batteries known in the art are rechargeable lithium batteries where the battery is able to undergo multiple discharge and recharge cycles. During discharge of a lithium cell, lithium ions are formed and extracted from the anode and inserted into the cathode. On recharge, the reverse process occurs. The electrodes used in these batteries can have a dramatic effect on the performance ofthe battery and, in particular, cycle life. Another class of lithium batteries known in the art are lithium primary batteries. A primary battery differs from a rechargeable battery in that it is only designed to be discharged once. In fact, because ofthe design, attempts to recharge a primary battery may create safety problems and may be only partially effective for a very limited number of cycles. Examples of lithium primary cells are described by Nishio et al in Handbook of Battery Materials, Chapter 2, "Practical Batteries^'", pp. 31-40, Elsevier, Amsterdam, (1999). For example, batteries based on Mnθ₂ cathodes provide a stable 3 V output, an operating temperature range of from -40 °C to +85 °C, and specific capacity from 90 mAh/g to approximately 120 mAh/g. Lithium primary cells based on a carbon monofluoride cathode operate at a nominal voltage of 3 V and exhibit specific capacities of up to approximately 120 mAh/g. A third type of primary cell reported by Nishio et al. is based on lithium-thionyl chloride. These cells possess a nominal voltage of 3.6 V and specific capacities in the range of 1 15 mAh/g to approximately 140 mAh/g, but suffer from safety concerns.

A number of other materials have been examined as cathode materials in lithium primary cells such as, for example, Bi₂O , Bi₂Pb₂O5, CuF₂, CuO, CuS, FeS, FeS₂, MoO , Ni S , and V O₅, as summarized by Linden in Handbook of Batteries, Chapter 14, pp. 5-6, McGraw-Hill, New York ( 1995). Primary, non-rechargeable cells with their single discharge have a short lifetime and their disposal burden is high, which makes the choice ofthe cathode material and its impact on the environment of great importance. Sulfur is an attractive cathode-active material for primary cells, both from an environmental perspective and from its very high theoretical specific capacity of 1675 mAh/g in the lithium-sulfur couple. L'.S. Pat. No. 4,410,609 to Peled et al. describes a primary cell comprising an anode consisting of lithium or a dischargeable alloy of lithium, an electrolyte comprising a solvent to dissolve both an electrolyte salt and polysulfides at a low concentration, and an inert porous cathode current collector, which may be loaded with sulfur. Yamin et al, in Electrochemical Society Proceedings, 1984, Volume 84-1, 301 -310, describe low rate lithium/sulfur batteries in which the primary cells have a porous carbon cathode current collector impregnated with sulfur and in which the cell's electrolyte is a lithium polysulfide saturated solution of 1M LiClO in tetrahydrofuran-toluene mixtures. The room temperature energy density for this cell is reported to be 730 Wh/Kg.

In a study of dioxolane-based solvents for lithium-sulfur batteries, Peled et al, in J. Electrochem. Soc, 1989, 136, 1621-1625, report that dioxolane-rich solvents are compatible with lithium but that sulfur utilization is only 50% due to the final reduction (discharge) product, Li S₂- Enhancement ofthe performance of primary electrochemical cells is of interest and importance. In studies on lithium/thionyl chloride cells, performance enhancement has been achieved by the addition of halide additives. For example, Linden, in Handbook of Batteries, Chapter 14, pp. 44-47, McGraw-Hill, New York (1995), summarizes data showing an increase in cell voltage and energy density by the addition of BrCl to lithium/thionyl chloride cells. In U.S. Pat. Nos. 4,784,925 and 4,784,927 to Klinedinst et al, small quantities of iodine or iodine monochloride are reported to act as catalysts to increase output voltage and output capacity of lithium/thionyl chloride cells.

Despite the various approaches proposed for the fabrication of lithium primary cells, there remains a need for higher energy density and safer and more environmentally acceptable primary cells.

It is, therefore, an object of the present invention to provide lithium primary cells which have high energy density, which are safe, and which comprise environmentally acceptable materials.

SUMMARY OF THE INVENTION

The present invention pertains to a primary electrochemical cell comprising: (a) a lithium anode; (b) a cathode comprising an electroactive sulfur-containing material; and (c) a non-aqueous electrolyte interposed between the anode and the cathode, which electrolyte comprises: (i) one or more non-aqueous electrolyte solvents; and (ii) one or more voltage-enhancing reactive components, which voltage-enhancing reactive components are non-electroactive.

In one embodiment, the one or more voltage-enhancing reactive components are selected from the group consisting of organic halides, inorganic halides, and phosphorus chalcogenides.

In one embodiment, the organic halide is of the formula:

R_fX wherein: R_f is CF (CF₂)_n, where n is an integer from 0 to 10; and

X is selected from the group consisting of F, Cl, Br, I, SO₂F, SO₂Cl, SO₂Rf, SOR_t, CO₂R_f, OR_f, SO₂Rf', SOR,¹, CO₂R_f', and OR_f', wherein Rf¹ is (CF₂)_PY, where p is an integer from 1 to 10, and Y is selected from the group consisting of F, Cl, Br, I, SO₂F, SO₂Cl, SO₂R, SOR,, CO₂R_f, and OR_f

In one embodiment, the organic halide is selected from the group consisting of perchloroalkanes, perchloroalkenes, and perchlorocycloalkenes In one embodiment, the inorganic hahde is selected from the group consisting of

A1F₃, A1C1₃, BF₃, BC1₃, MgCl₂, PF PCL, PC1₅, S1CI4, TιCl₄, SF₄, and SF₆

In one embodiment, the phosphorus chalcogemde is selected from the group consisting of P2S5, P₄Sιo, P2O5, P₄Oιo, and phosphorus oxysulfides

In one embodiment, the one or more non-aqueous electrolyte solvents are selected from the group consisting of ethers, cyclic ethers, polyethers, carbonates, esters, sulfones, sulfites, and sulfolanes

In one embodiment, one or more ofthe voltage-enhancing reactive components is a non-aqueous electrolyte solvent

In one embodiment, the non-aqueous electrolyte further comprises one or more lithium salts In one embodiment, the one or more lithium salts are selected irom the group consisting of LiBr, Lil, LiSCN, LιBF₄, LιPF₆, LιAsF_ό, LιSO^CF₃, LιN(SO₂CF,)₂ LιC(SO₂CF₃)₃, (LιS_x)_zR, and Lι S_x, where x is an integer from 1 to 20, z is an integer from 1 to 3, and R is an organic group

In one embodiment, the non-aqueous electrolyte comprises Lι₂S_x, where x is an integei from 1 to 20

In one embodiment, the electroactive sulfur-contaming material comprises elemental sulfur In one embodiment, the electroactive sulfur-conta ing matenal, in its oxidized state, comprises one or more polysulfide moieties, -S_m-, where m is an integer equal to or greater than 3 In one embodiment, the electroactive sulfur-containing material, in its oxidized state, comprises one or more polysulfide moieties, -S_m , where m is an integer equal to or greater than 3 In one embodiment, the electroactive sulfur-containing material, in its oxidized state, comprises one or more polysulfide moieties, S_m ² , where m is an integer equal to or greater than 3

In one embodiment, the electroactive sulfur-contaming material, in its oxidized state, is of the general formula

-τ C(S_x) wherein x ranges from greater than 2.5 to about 50, and n is an integer equal to or greater than to 2. In one embodiment, the electroactive sulfur-containing material, in its oxidized state, comprises one or more of the polysulfur moieties:

wherein m, the same or different at each occurrence, is an integer and is greater than 2, and y, the same or different at each occurrence, is an integer and is equal to or greater than 1.

In one embodiment, the electroactive sulfur-containing material, in its oxidized state, comprises one or more ofthe moieties:

wherein m is the same or different at each occurrence, is an integer, and is greater than 2.

In one embodiment, the electroactive sulfur-containing material is a polymer comprising polymeric segments of the formula;

wherein:

Q denotes a carbocyclic repeat unit comprising a carbocycle having from 3 to 12 ring carbon atoms;

S denotes a sulfur atom; m is the number of sulfur atoms in a given polysulfide linkage, is an integer from 3 to 10, and is the same or different at each occurrence; n denotes the number of crosslinkmg polysulfide linkages, is an integer from 1 to 20. and is the same or different at each occurrence; and p is an integer greater than 1.

In one embodiment, the electroactive sulfur-contaming material comprises greater than 50% by weight of sulfur In a preferred embodiment, the electroactive sulfur- containing material comprises greater than 75% by weight of sulfur In a more preferred embodiment, the electroactive sulfur-contammg material comprises greater than 90% by weight of sulfur.

In one embodiment, the lithium anode is selected from the group consisting of lithium metal, hthium-alummum alloys, hthium-tin alloys, hthium-mtercalated carbons, and hthium-mtercalated graphites

In one embodiment, the cell voltage is greater than 2 5 V In one embodiment, the cell voltage is greater than 2.8 V In one embodiment, the cell voltage is greater than 3 0 V In one embodiment, the energy density of the cell is greater than 1000 Wh/Kg In one embodiment, the energy density of the cell is greater than 1200 Wh/Kg In one embodiment, the energy density of the cell is greater than 1500 Wh/Kg

Another aspect of the present invention pertains to a method of making a lithium primary electrochemical cell comprising the steps of: (a) providing a lithium anode; (b) providing a cathode comprising an electroactive sulfur-contammg material, and (c) interposing a non-aqueous electrolyte between the anode and the cathode, wherein the electrolyte comprises (l) one or more non-aqueous electrolyte solvents, and (n) one oi more voltage-enhancing reactive components, as described herein, which voltage- enhancing reactive components are non-electroactive As will be appreciated by one of skill m the art, features of one aspect oi embodiment of the invention are also applicable to othei aspects or embodiments of the invention BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the discharge voltage vs time for a hfhium-sulfur primary cell with 0 5 M lithium bιs(tπfluoromethyl sulfonyl) lmide m a l l mixture of ethylene sulfite and propylene carbonate as electrolyte

Figure 2 shows the discharge voltage vs time for a lithium-sulfur primary cell with 0 5 M lithium bιs(tπfluoromethyl sulfonyl) lmide in 1,3-dιoxolane as electrolyte

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present invention pertains to lithium primary batteries in which the cathode comprises an electroactive sulfur-contaming material, the anode comprises a lithium metal compound, and the non-aqueous electrolyte comprises voltage-enhancing reactive components, which are non-electroactive, and which enhance the voltage ofthe primary cell

Cathodes

The term "electroactive sulfur-contaming material," as used herein, relates to cathode active materials which comprise the element sulfur in any form, wherein the electrochemical activity involves the breaking or forming of sulfur-sulfur covalent bonds

Suitable electroactive sulfur-contammg materials, include, but are not limited to, elemental sulfur and organic materials comprising sulfur atoms and carbon atoms, which may or may not be polymeric Suitable organic materials include those further comprising heteroatoms, conductive polymer segments, composites, and conductive polymers In one embodiment, the electroactive sulfur-contammg material comprises elemental sulfur In one embodiment, the electroactive sulfur-containing material comprises a mixture of elemental sulfur and a sulfur-contammg polymer

In one embodiment, the sulfur-contaming material, in its oxidized state, comprises a polysulfide moiety, S_m, selected from the group consisting of covalent -S_m- moieties, ionic -S_m moieties, and ionic S_m ² moieties, wherein m is an integer equal to or greater than 3, such as for example, elemental sulfur and sulfur-contaming polymers In one embodiment, m ofthe polysulfide moiety, S_m, is an integer equal to or greater than 6 In one embodiment, m ofthe polysulfide moiety, S_m, is an integer equal to or greater than 8 In one embodiment, the sulfur-contammg material is a sulfur-contammg polymei In one embodiment, the sulfur-contam g polymer has a polymer backbone chain and the polysulfide moiety, S_m, is covalently bonded by one or both of its terminal sulfur atoms as a side group to the polymer backbone chain In one embodiment, the sulfur-contammg polymer has a polymer backbone chain and the polysulfide moiety, S_m, is incorporated into the polymer backbone chain by covalent bonding of the terminal sulfur atoms of the polysulfide moiety

The specific capacity (mAh/g or Ah/Kg) or energy density (Wh/Kg) in electroactive sulfur-contammg materials is directly related to the number of electrons participating in the reduction/oxidation (discharge/charge) process For a disulfide group, (R'-S-S-R", where R' and R" are independently an organic group), two electrons participate in the discharge/charge process For higher polysulfides, two electrons participate in each sulfur-sulfur bond reduction It can be readily appreciated that increased energy densities are obtained m higher polysulfides compared with disulfides In one embodiment, the electroactive sulfur-containing material comprises greater than 50% by weight of sulfur In a preferred embodiment, the electroactive sulfur- conta ing material comprises greater than 75% by weight of sulfui In a more preferred embodiment, the electroactive sulfur-contaming material comprises greater than 90% by weight of sulfur The nature of the electroactive sulfur-contaming materials useful in the practice of this invention may vary widely Further examples of suitable electroactive sulfur- containing materials include, but are not limited to,

(a) an electroactive polycarbon-sulfide material, which, in its oxidized state, is of the general formula C(S_x) L_n wherein x ranges from greater than 2 5 to about 50, and n is an integer equal to or greater than to 2, as described m U S Pat Nos 5,601 ,947 and 5,690,702 to Skotheim et al , and which, in its oxidized state, may comprise one or more of the polysulfui moieties

wherein m, the same or different at each occurrence, is an integer and is greater than 2, and y, the same or different at each occurrence, is an integer and is equal to or greater than 1 ; (b) an electroactive polyacetylene co-polysulfur material, which, in its oxidized state, is ofthe general formula:

wherein x ranges from greater than 1 to about 100, and n is an integer equal to or greater than 2, as described in U.S. Pat. Nos. 5,529,860 and 6,117,590 to Skotheim et al, and which, in its oxidized state, may comprise one or more ofthe moieties:

wherein m, the same or different at each occurrence, is greater than 2; and

(c) an electroactive, highly crosslinked organic polymer, which polymer comprises polymeric segments of the formula;

wherein:

S denotes a sulfur atom; m is the number of sulfur atoms in a given polysulfide linkage, is an integer from 3 to 10, and is the same or different at each occurrence; n denotes the number of crosslinking polysulfide linkages, is an integer from 1 to 20, and is the same or different at each occurrence; and p is an integer greater than 1; as described in U.S. Pat. Application Ser. No. 08/995,1 12 to Gorkovenko et al. ofthe common assignee and PCT Publication No. WO 99/33130. Other suitable electroactive sulfur-containing materials comprising polysulfide linkages include, but are not limited to, those described in U.S. Pat. No. 4,664,991 to Perichaud et al, and in U.S. Pat. Nos. 5,723,230, 5,783,330, 5,792,575 and 5,882,819 to Naoi et al. Other examples of suitable electroactive sulfur-containing materials include organo-sulfur materials comprising disulfide linkages, although their low specific capacity compared to the corresponding materials comprising polysulfide linkages makes it highly difficult to achieve the high capacities desired for practical electrochemical cells. However, they may be utilized in a blend with elemental sulfur and/or with sulfur- containing polymers comprising a polysulfide moiety in the cathodes of this invention, and may contribute by their electrochemical properties, by their interaction with lithium polysulfides and lithium sulfides generated during the cycling of the cells, and, optionally, by their melting properties during cell fabrication, to achieve the desired high capacities m the electrochemical cells or batteries of the present invention. Examples of electroactive sulfur-containing materials comprising disulfide groups include those described in U.S. Pat. No. 4,739,018 to Armand et al; U.S. Pat. Nos. 4,833,048 and 4,917,974, both to De Jonghe et al; U.S. Pat. Nos. 5,162,175 and 5,516,598, both to Visco et al; and U.S. Pat. No. 5,324,599 to Oyama et al

The cathodes ofthe lithium cells of the present invention may further comprise one or more conductive fillers to provide enhanced electronic conductivity. Examples of conductive fillers include, but are not limited to, those selected from the group consisting of conductive carbons, graphites, activated carbon fibers, non-activated carbon nanofibers, metal flakes, metal powders, metal fibers, carbon fabrics, metal mesh, and electrically conductive polymers. The amount of conductive filler, if present, is preferably in the range of 2 to 30 % by weight. The cathodes may also further comprise other additives including, but not limited to, metal oxides, aluminas, silicas, and transition metal chalcogenides.

The cathodes of the lithium cells of the present invention may also comprise a binder. The choice of binder material may vary widely so long as it is inert with respect to the other materials in the cathode. Useful binders are those materials, usually polymeric, that allow for ease of processing of battery electrode composites and are generally known to those skilled in the art of electrode fabrication. Examples of useful binders include, but are not limited to, those selected from the group consisting of polytetrafluoroethylenes (Teflon®), polyvmyhdene fluondes (PVF₂ or PVDF), ethylene-propylene-diene (EPDM) rubbers, polyethylene oxides (PEO), UV curable acrylates, UV curable mefhacrylates, and heat curable divinyl ethers, and the like The amount of binder, if present, is preferably in the range of 2 to 30%> by weight The cathodes ofthe lithium cells ofthe present invention may further comprise a current collector as is known m the art Current collectors are useful in efficiently collecting the electrical current generated throughout the cathode and in providing an efficient surface for attachment ofthe electrical contacts leading to the external circuit as well as functioning as a support for the cathode Examples of useful current collectors include, but are not limited to, those selected from the group consisting of metallized plastic films, metal foils, metal grids, expanded metal grids, metal mesh, metal wool, woven carbon fabric, woven carbon mesh, non-woven carbon mesh, and carbon felt

Cathodes ofthe lithium cells of the present invention may be prepared by a variety of methods For example, one suitable method comprises the steps of (a) dispersing oi suspending in a liquid medium the electroactive sulfur-contammg material, as described herein, (b) optionally adding to the mixture of step (a) a conductive filler, binder, or other cathode additives, (c) mixing the composition resulting from step (b) to disperse the electroactive sulfur-contaming material, (d) casting the composition resulting from step (c) onto a suitable substrate, and (e) removing some or all of the liquid from the composition resulting from step (d) to provide the cathode

Examples of suitable liquid media for the preparation of cathodes of the present invention include aqueous liquids, non-aqueous liquids, and mixtures thereof Especially preferred liquids are non-aqueous liquids such as, for example, methanol, ethanol, isopropanol, propanol, butanol, tetrahydrofuran, dimethoxyethane, acetone, toluene, xylene, acetonitπle, and cyclohexane

Mixing of the various components can be accomplished using any of a variety of methods known in the art, so long as the desired dissolution or dispersion of the components is obtained Suitable methods of mixing include, but are not limited to, mechanical agitation, grinding, ultrasomcation, ball milling, sand milling, and impingement milling

The formulated dispersions can be applied to substrates by any of a variety of coating methods known in the art and then dried using techniques, known in the art, to form the solid cathodes ofthe lithium cells of this invention Suitable hand coating techniques include, but are not limited to, the use of a wire-wound coating rod or gap coating bar Suitable machine coating methods include, but are not limited to, the use of roller coating, gravure coating, slot extrusion coating, curtain coating, and bead coating Removal of some or all of the liquid from the mixture can be accomplished by any of a variety of means known in the art Examples of suitable methods for the removal of liquids from the mixture include, but are not limited to, hot air convection, heat, infrared radiation, flowing gases, vacuum, reduced pressure, and by simply air drying

The method of preparing the cathodes of the present invention may further comprise heating the electroactive sulfur-contammg material to a temperature above its melting point and then resolidifying the melted electroactive sulfur-contammg material to form a cathode active layer having redistributed sulfur-containing material of higher volumetric density than before the melting process

Voltage-enhancing Electrolyte Reactive Components The term "non-electroactive," as used herein, pertains to a material which does not take part in the electrochemical reaction of discharge m the absence of the electroactive sulfur-containing material of the cathode

The tenn "voltage," as used herein, pertains to electrical potential differences between a positive electrode measured relative to a Lι/Lι⁺ reference electrode, except where otherwise noted The term "voltage," as used herein, also pertains to the average voltage during discharge, unless otherwise noted The term "open-circuit voltage," as used herein, pertains to cell voltage under a no-load condition

The terms "primary cells," or "primary batteries," as used herein, pertain to electrochemical cells in which an essentially irreversible chemical reaction geneiates electricity, or which depletes a necessary component during discharge such that recharging is prevented or relatively inefficient, and to electrochemical cells that cannot be recharged at all, or at best recharged with poor efficiency The terms "battery" and "cell" are used herein interchangeably A battery may comprise one or more electrochemical cells

The term "Li/S cell", as used herein, pertains to an electiochemical cell comprising a lithium anode and an electroactive sulfur-contammg matenal, as described herein, as a cathode active matenal Likewise, the term "S", as used in the description of voltage enhancement, pertains to the element sulfur and to electroactive sulfur-contammg matenals In one aspect ofthe present invention, the electrolyte voltage-enhancing reactive components ofthe lithium primary batteries increase the voltage ofthe cell. Typically, the cell voltage of a Li/S cell is approximately 2.2 V. Suitable voltage-enhancing reactive components in the present invention increase the voltage ofthe Li/S cell by more than 0.1 V, i.e. to values higher than 2.3 V. In other words, Li + S + Z provides a voltage greater than 2.3 V, where Z is the voltage-enhancing reactive component.

Theoretical calculations from the Gibbs relationship, ΔG = -nFE, can be used to select candidate voltage-enhancing reactive components, Z. For example, for the reaction

6 Li + 3 S + 2A1C1₃ -> 6 LiCl + A1₂S₃ the theoretical voltage can be calculated as follows: E (in volts) = -ΔG/nF; where ΔG is the difference in Gibbs energy between reactants and products, F is the Faraday constant, and n is the number of electrons. The Gibbs energy values used in the calculations, taken from the Handbook of Chemistry and Physics, Vol. 73, CRC Press, Boca Raton (1992), are as follows; for A1C1₃, -628.8 KJ/mol; for LiCl, -384.4 KJ/mol; for A1₂S₃, -724 KJ/mol; and F (the Faraday constant) is 96.49 Kcoulombs/mol. Thus, for the above example:

E (in volts) = -[ 2(628.8) - [6(384.4)+ 7241 ] = 1772.8 = 3.06 V (96.49)6 578.9

Energy density is calculated by dividing ΔG by product weight. Energy density for the above reaction is 1772.8/404.5 = 4.383 KJ/g or 4383 KJ/Kg or 1217 Wh/Kg. Representative calculated values are shown in Table 1.

Suitable voltage-enhancing reactive components for use in the present invention include inorganic halides, phosphorus chalcogenides, and organic halides. Inorganic halides include, but are not limited to, A1F₃, A1C1₃, BF₃, BC1₃, MgCl₂, PF₅, PC1₃, POCI₃, PCI;,, T1CI4, SF , and SF₆ Phosphorus chalcogenides include, but are not limited to, the group consisting of P₂S₅, P₄Sιo, P₂O₅, P4O10, and phosphorus oxysulfides, such as P₂O₃S₂, P₂O2S3, P₄O₄S3, and P₆OιoSs Complex anion denvatives of suitable inorganic halides or phosphorus chalcogenides may also be suitable voltage-enhancmg reactive components m the present invention, including for example, but not limited to, PF₆ , BF₄ , PS₄' , and PSi Organic halides include, but are not limited to, perchloroalkanes, perchloroalkenes, perchlorocycloalkenes, chlorofluorocarbons, bromofluorocarbons, perfluoroalkanes, and denvatives of the foregoing containing polar functional groups, such as sulfone, -SO?- sulfoxyl, -SO-, chlorosulfonyl, -SO₂Cl, and fluorosulfonyl, SOiF Other suitable organic halides are moieties ofthe formula

R_fX wherein

Rι is CFi(CF₂)_n, where n is an integer from 0 to 10, and

X is F, Cl, Br, I, SO₂F, SO₂Cl, SO₂R,, SOR,. CO₂R, OR,, SO.R,¹ , SOR, ¹, CO₂R

wherein R_f ¹ is (CF₂)_PY, where p is an integer from 1 to 10, and Y is selected from the group consisting of F, Cl, Br, I, SO₂F, SO₂Cl, SO₂R,, SOR,, CO₂R,, and OR,

In one embodiment of the present invention, the one or moie voltage-enhancing reactive components comprise a mixture selected from the group consisting of inorganic halides and organic halides, inorganic halides and phosphorus chalcogenides, and phosphorus chalcogenides and organic halides

The amount of the voltage-enhancmg reactive component useful in the present invention may vary over a wide range In one embodiment, the amount of the voltage- enhancing leactive components is equal to or gi eater than 5% bv weight ofthe non- aqueous electrolyte In one embodiment, the amount of the voltage-enhancing reactive components is equal to or greater than 10% by weight of the non-aqueous electrolyte However, the voltage-enhancmg reactive component is consumed during the discharge of the cell, for example, as shown in the equations of Table 1 Voltage enhancement will not be achieved after the voltage-enhancmg reactive component is consumed It is thus preferred to provide an amount of the voltage-enhancmg reactive component at least equal to the amount required by the stoichiometry ofthe cell reactions, for example, as shown m the equations of Table 1 While not wishing to be bound by any theory, the voltage-enhancing reactive components, while not electrochemically active per se, may function, for example, by reacting with polysulfide species generated in the cell during discharge to form electrochemically active organic polysulfides. For example, a voltage-enhancing reactive component, Z'-C-F, comprising a carbon-fluorine bond, C-F, where Z'-C-F is, for example, CF , may chemically react with lithium polysulfide to generate lithium fluoride and an electroactive organic polysulfide, as for example illustrated below:

Li₂ S_λ + Z'-C-F ^ LiF + LiS_x-C-Z' where x is an integer from 2 to 20. The voltage-enhancing reactive component Z changes Gibbs energy due to generation of different and additional reaction products, for example, LiCl or LiF instead of Li₂S. Voltage may be higher due to the higher Gibbs energy per mole of components involved in the reaction. At the same time, energy density (Wh Kg) could be lower due to higher total weight of components. Voltage increase with the voltage-enhancing reactive component Z may be observed if the reaction between generated polysulfides and the voltage-enhancing reactive component Z is sufficiently fast. In other words, this chemical reaction between polysulfides and Z should be fast enough so that separate steps are not observed during discharge of the cell. Ideally, to achieve maximum voltage enhancement from the system, the reaction should proceed in one step, for example, where Z is Z"-F:

2Li + S + Z"-F - LiF + Li-S-Z" At faster rates, for example, the (Li + S + Z-F) voltage will be closer to thermodynamic voltage or higher, while at slower rates only the (Li + S) reaction voltage will be observed. Reaction rates also may depend on the nature of the electrolyte. Selection of a suitable electrolyte is, therefore, very important for the functioning ofthe voltage- enhancmg reactive component. For example, a 0.6 M solution of AICI₃ in diethoxyethane generates a voltage of only 2.17 V for the Li/S cell, which is typical for a polysulfide- forming Li + S reaction. A solution of 0.6 M AICI₃ in sulfolane generates 2.75 V, which is closer to the calculated voltage for the Li + S + AICI₃ reaction. In other words, AICI₃ functions as a reactive voltage-enhancing reactive component in sulfolane electrolyte solvent, but not in diethoxyethane electrolyte solvent.

In embodiments in which one or more of the voltage-enhancing reactive components of the electrolyte is a non-aqueous electrolyte solvent, the one or more ofthe electrolyte solvents may be consumed or partially consumed during discharge of the cell. When the electrolyte reactive component comprises an electrolyte solvent, it is desirable that the total volume of non-aqueous electrolyte solvent be such that there remains sufficient electrolyte solvent in the cell at complete discharge to provide conductivity. Non-aqueous electrolyte solvents which may be used as voltage-enhancing reactive components include, but are not limited to, sulfites. Voltage-enhancing reactive components, including non-aqueous electrolyte solvents such as sulfites, may additionally function to enhance storage stability, improve self discharge, and increase safety of the cells of the present invention. It has been noted in lithium cells with electroactive sulfur-containing materials as cathodes, for example by Peled et al, in J. Electrochem. Soc, 1989, 136, 1621-1625, that full capacity ofthe sulfur is not obtained due to the reduction (discharge) stopping at Li₂S₂, which has a remaining S-S bond. The voltage-enhancing reactive components of the present invention may also function to release the energy of all S-S bonds, for example, by reactions with Li₂S₂- In other words, the voltage-enhancing reactive components may also function to enhance the capacity in lithium batteries comprising electroactive sulfur- containing materials as a cathode active material. In one embodiment, by enhancing the complete reduction or discharge of the electroactive sulfur-containing materials, capacity enhancing components, such as those described in co-pending U.S Patent Application entitled "Lithium Batteries" to Mikhaylik et al, of the common assignee, filed on even date herewith, may be used in conjunction with the voltage-enhancing reactive components of the present invention.

Although these voltage-enhancing reactive components increase the lithium/sulfur cell voltage, in some instances this benefit may be offset by a reduction in energy density. The calculated data in Table 1 illustrate this behavior. For example, additive AICI₃ is calculated to produce a cell voltage of 3.062 V with an energy density of 1217 Wh/Kg. This cell voltage is higher than the calculated value, 2.287 V, without the additive, but the calculated cell energy density is lower than the 2669 Wh/Kg without the additive. Suitable organic halide components may be expected to increase cell voltage comparable to the increases calculated in Table 1 for carbon tetrachloride and carbon tetrafluoride. The energy density for higher homologs of these halides will be lower than the values for carbon tetrachloride and carbon tetrafluoride since the energy density is inversely proportional to the C-Cl or C-F equivalent weight, respectively. Preferred reactive components increase the voltage ofthe cell by more than 0.3 V or to greater than 2.5 V for the typical sulfur-containing electrochemical cell of this invention. More preferred reactive components increase the voltage ofthe cell by more than 0.6 V or to greater than 2.8 V. Most preferred reactive components increase the voltage ofthe cell by more than 0.8 V or to greater than 3.0 V.

In one embodiment, the cells ofthe present invention comprising voltage enhancing reactive components have an energy density of greater than 1000 Wh Kg. In a preferred embodiment, the cells ofthe present invention comprising voltage enhancing reactive components have an energy density of greater than 1200 Wh/Kg. In a more preferred embodiment, the cells ofthe present invention comprising voltage enhancing reactive components have an energy density of greater than 1500 Wh/Kg.

The term "energy density," as used herein, relates to cell energy based on the sum ofthe weights of the anode active components, the cathode active components, and the voltage-enhancing reactive components, for example as illustrated in the method used in calculating the theoretical energy densities shown in Table 1.

Electrolytes, Separators, and Electrochemical Cells.

The electrolytes used in electrochemical or battery cells function as a medium for the storage and transport of ions, and in the special case of solid electrolytes and gel electrolytes, these materials may additionally function as a separator between the anode and the cathode. Any liquid, solid, or gel material capable of storing and transporting ions may be used, so long as the material is electrochemically and chemically unreactive with respect to the anode and the cathode, and the material facilitates the transport of lithium ions between the anode and the cathode. The electrolyte must also be electronically non- conductive to prevent short circuiting between the anode and the cathode.

Typically, the electrolyte comprises one or more ionic electrolyte salts to provide ionic conductivity and one or more non-aqueous liquid electrolyte solvents, gel polymer materials, or polymer materials. Suitable non-aqueous electrolytes for use in the present invention include, but are not limited to, organic electrolytes comprising one or more materials selected from the group consisting of liquid electrolytes, gel polymer electrolytes, and solid polymer electrolytes. Examples of non-aqueous electrolytes for lithium batteries are described by Dominey in Lithium Batteries, New Materials, Developments and Perspectives, Chapter 4, pp. 137-165, Elsevier, Amsterdam (1994). Examples of gel polymer electrolytes and solid polymer electrolytes are described by Alamgir et al. in Lithium Batteries, New Materials, Developments and Perspectives, Chapter 3, pp. 93-136, Elsevier, Amsterdam (1994).

Examples of useful non-aqueous liquid electrolyte solvents include, but are not limited to, non-aqueous organic solvents, such as, for example, N-methyl acetamide, acetonitrile, acetals, ketals, sulfones, sulfolanes, aliphatic ethers, cyclic ethers, glymes, polyethers, phosphate esters, siloxanes, dioxolanes, N-alkylpyrrolidones, substituted forms ofthe foregoing, and blends thereof. Fluorinated derivatives ofthe foregoing are also useful. Examples of ethers include, but are not limited to, dimethyl ether, diethyl ether, methylethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dimethoxymethane, trimefhoxymefhane, dimethoxyethane, diethoxyethane, 1 ,3-dimethoxypropane, tetrahydrofuran, tetrahydropyran, 1,4-dioxane, and 1,3-dioxolane.

Examples of polyethers include, but are not limited to, diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), higher glymes, diethylene glycol divinylether, and triethylene glycol divinylether.

Examples of sulfones include, but are not limited to, sulfolane, 3-methyl sulfolane, 3-sulfolene, and non-symmetrical, non-cyclic sulfones, and fluorinated or partially fluorinated derivatives ofthe foregoing. The specific choice of solvent will depend on several factors including self discharge. The term "self discharge," as used herein, relates to the loss of capacity, or charge, when no external load is applied to the cell. An electrolyte comprising one or more non-aqueous electrolyte solvents and one or more electrolyte salts typically interacts with the lithium anode surface to form a solid electrolyte interface (SEI). The SEI allows passage of lithium ions as the cell discharges and at the same time it is desirable that the SEI protects the lithium surface from further reactions with electrolyte, cathode discharge products, or other soluble components ofthe cathode. In cells comprising electroactive sulfur-containing materials, the SEI should protect the lithium from self discharge, for example, from reaction with possible cathode discharge products such as sulfide ions, polysulfide ions, and other sulfur containing ions, and soluble cathode components such as sulfur. Preferred electrolyte solvents are those which provide low self discharge rates.

These liquid electrolyte solvents are themselves useful as plasticizers for gel polymer electrolytes. Examples of useful gel polymer electrolytes include, but are not limited to, those comprising one or more polymers selected from the group consisting of polyethylene oxides, polypropylene oxides, polyacrylonitriles, polysiloxanes, polyimides, polyphosphazenes, polyethers, sulfonated polyimides, perfluorinated membranes (NATION™ resins), polydivinyl polyethylene glycols, polyethylene glycol diacrylates, polyethylene glycol dimethacrylates, derivatives ofthe foregoing, copolymers ofthe foregoing, crosslinked and network structures of the foregoing, and blends ofthe foregoing, and optionally plasticizers.

Examples of useful solid polymer electrolytes include, but are not limited to, those comprising one or more polymers selected from the group consisting of polyethers, polyethylene oxides, polypropylene oxides, polyimides, polyphosphazenes, polyacrylonitriles, polysiloxanes, derivatives of the foregoing, copolymers ofthe foregoing, crosslinked and network structures ofthe foregoing, and blends ofthe foregoing.

In addition to solvents, gelling agents, and polymers as known in the art for forming non-aqueous electrolytes, the non-aqueous electrolyte may further comprise one or more ionic electrolyte salts, also as known in the art, to increase the ionic conductivity. Examples of ionic electrolyte salts for use in the present invention include, but are not limited to, LiSCN, LiBr, Lil, LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆, LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂. Other electrolyte salts useful in the practice of this invention include lithium polysulfides (Li₂S_x), and lithium salts of organic ionic polysulfides (LiS_xR)_n, where x is an integer from 1 to 20, n is an integer from 1 to 3, and R is an organic group, and those disclosed in U.S. Pat. No. 5,538,812 to Lee et al. The lithium polysulfides, Li₂S_x, may be formed in situ in Li/S cells by self discharge of the cell or during the discharge ofthe cell. Preferred ionic electrolyte salts are LiBr, Lil, LiSCN, LiBF₄, LiPF₆, LiAsF₆, LiSO₃CF₃, LiN(SO₂CF₃)₂. and LiC(SO₂CF₃) .

The electrochemical cells of the present invention may further comprise a separator interposed between the cathode and anode. Typically, the separator is a solid non- conductive or insulative material which separates or insulates the anode and the cathode from each other preventing short circuiting, and which permits the transport of ions between the anode and the cathode.

The pores of the separator may be partially or substantially filled with electrolyte. Separators may be supplied as porous free standing films which are interleaved with the anodes and the cathodes during the fabrication of cells. Alternatively, the porous separator layer may be applied directly to the surface of one ofthe electrodes, for example, as described in PCT Publication No. WO 99/33125 to Carlson et al. and in U.S. Pat. No. 5,194,341 to Bagley et al.

A variety of separator materials are known in the art. Suitable solid porous separator materials include, but are not limited to, polyolefms, such as, for example, polyethylenes and polypropylenes, glass fiber filter papers, and ceramic materials. Further examples of separators and separator materials suitable for use in this invention are those comprising a microporous pseudo-boehmite layer, which may be provided either as a free standing film or by a direct coating application on one of the electrodes, as described in U.S. Pat. Application Ser. Nos. 08/995,089 and 09/215,1 12 by Carlson el al, ofthe common assignee. Solid electrolytes and gel electrolytes may also function as a separator in addition to their electrolyte function.

In one embodiment, the solid porous separator is a porous polyolefin separator. In one embodiment, the solid porous separator comprises a microporous pseudo-boehmite layer.

Cells and batteries of the present invention may be made in a variety of sizes and configurations which are known to those skilled in the art. These battery design configurations include, but are not limited to, planar, prismatic, jelly roll, w-fold, stacked, and the like. Although the methods ofthe present invention are particularly suitable for use with thin film electrodes, they may also be beneficial in thick film designs.

It is generally accepted that, when low electric currents are desired, the electrodes within the cell should have as much mass and as little surface area as possible. At the expense of power density, this provides for increased energy density while low electrode surface area minimizes undesirable self-discharge reactions. Conversely, when larger electrical discharge currents are required, electrode surface area and power density are maximized at the expense of energy density and self-discharge rate. Thin film electrodes provide high surface area and thereby high power density. Thin film electrodes may be incorporated into a number of battery design configurations, such as prismatic, jelly roll, w-fold, and stacked configurations. Alternatively, designs incorporating both low and high surface area regions, as described in U.S. Pat. Nos. 5,935,724 and 5,935,728 to Spillman et al, may be incorporated into jelly roll and other configurations.

Thin film electrodes, in particular, may be configured into prismatic designs. With the drive to conserve weight, thin film barrier materials are particularly preferred, e.g., foils For example, PCT Publication No WO 99/30133 to Thibault et al describes methods for preparing pnsmatic cells in which suitable barrier materials for sealed casings, methods of filling cells with electrolyte, and methods of sealing the casing, are described

EXAMPLES

Several embodiments of the present invention are described in the following examples, which are offered by way of illustration and not by way of limitation

Example 1

A cathode was prepared by coating a mixture of 75 parts of elemental sulfur (available from Aldπch Chemical Company, Milwaukee, WI), 15 parts of a conductive carbon pigment PRJNTEX XE-2 (a trademark for a carbon pigment available from Degussa Corporation, Akron, OH), and 10 parts of PYROGRAF-III (a tradename for carbon filaments available from Applied Sciences, Inc , CedarviIIe, OH) dispersed in isopropanol onto a 17 micron thick conductive carbon coated aluminum foil substrate (Product No 60303 available from Rexam Graphics, South Hadley, MA) After drying and calendering, the coated cathode active layer thickness was about 27 microns The anode was lithium foil of about 50 microns in thickness The electrolyte was a 0 5 M solution of lithium bιs(tπfluoromethylsulfonyl) imide, (available from 3M Corporation, St Paul, MN) in a 50 50 volume ratio mixture of ethylene sulfite and propylene carbonate The porous separator used was 16 micron E25 SETELA (a trademark foi a polyolefin separator available from Tonen Chemical Corporation, Tokyo, Japan, and also available from Mobil Chemical Company, Films Division, Pittsford, NY) The above components were combined into a layered structure of cathode/separator/anode, which was wound and compressed, with the liquid electrolyte filling the void areas of the separator and cathode to form prismatic cells with an electrode area of about 800 cm² The cells were discharged at 150 mA (0 188 mA/cm²) to 1 25 V

The average voltage during the discharge was 2 42-2 43 V, as shown m Figure 1 Comparative Example 1

A cell was prepared by the procedure of Example 1 except that the electrolyte was a 0.5 M solution of lithium bis(trifluoromethylsulfonyl) imide in 1 ,3-dioxolane. The cell was discharged at 250 mA to 1.25 V. The average voltage during the discharge was 1.93 V to 1.83 V, as shown in Figure 2.

Example 2

A cathode was prepared by coating a mixture of 75 parts of elemental sulfur, 20 parts of a conductive carbon pigment PRINTEX XE-2, and 5 parts of PYROGRAF-III dispersed in isopropanol onto the 17 micron thick conductive carbon coated aluminum foil substrate of Example 1. After drying and calendering, the coated cathode active layer thickness was about 27 microns with a sulfur loading of 1.2 rag/cm^". The anode was lithium foil of about 50 microns in thickness. The porous separator used was 16 micron E25 SETELA. The components were combined into a layered structure of cathode/separator/anode with the liquid electrolyte filling the void areas of the separator and cathode to form button cells with an electrode area of about 2 cm^". The electrolyte was a 0.6 M solution of AICI₃ in sulfolane. This corresponds to about 6% by weight of AICI₃ in the non-aqueous electrolyte. The open-circuit voltage was found to be 2.75 V.

Example 3

Button cells were prepared by the procedure of Example 2 except that the electrolyte was 0.6 M AICI₃ in diethoxyethane. The open-circuit voltage was found to be only 2.17 V.

Example 4

Button cells were prepared by the procedure of Example 2 except that the electrolyte was a 0.75 M solution of lithium bis(trifluoromefhylsulfonyl) imide in ethylene sulfite. The open-circuit voltage was found to be 2.80 V.

Comparative Example 2

A cathode slurry, with a solid content of 14% by weight, was prepared in a solvent mixture of 80%o isopropanol, 12% water, 5% l-methoxy-2-propanol and 3% dimethyl ethanolamine (by weight). The solid slurry components were elemental sulfur, 65% by weight, Prmtex XE-2, 15% by weight, graphite (available from Fluka/Sigma-Aldπch, Milwaukee, WI), 15% by weight, TA22-8 resm (a trade name for an ethyl acrylate-acryhc acid copolymer available from Dock Resms Corporation, Lmden, NJ), 4% by weight, and Ionac PFAZ-322 (a trade name for tπmethylol propane tπs [β-(N-2-methyl aziπdinyl) propionate], available from Sybron Chemicals Inc , Birmingham, NJ), 1 % by weight The slurry was coated by a slot die coater onto both sides of a 17 micron thick conductive carbon coated aluminum foil (Product No 60303, Rexam Graphics) as a current collector The coating was dried in the ovens of a slot die coater The lesulting dry cathode active layer had a thickness of about 26 microns on each side of the current collector, with a loading of electroactive cathode material of about 1 1 rag/cm

A cell was fabricated from the coated cathode, where the anode was lithium foil of about 50 microns in thickness, and the porous separator used was 16 micron E25 SETELA The above components were combined into a layered structure of cathode/separator/anode The cell with an electrode area of about 1 cm" was inserted into a vial to which was added 1 mL of electrolyte The electrolyte was a 0 5 M solution of lithium bιs(tπfluoromethylsulfonyl) imide in sulfolane saturated with sulfui The cell was discharged at a discharge current of 0 1 mA/cm^", and the voltage at the mid point of the discharge determined Table 2 summarizes the results

Example 5

Cells were prepared and discharged by the method of Comparative Example 2 except that the electrolyte was a 0 5 M solution of lithium bιs(tπfluoromethylsulfonyl) imide in sulfolane saturated with sulfur, to which was added 10 % by weight of CC1₄

Example 6

Cells were prepared and discharged by the method of Comparative Example 2 except that the electrolyte was a 0 5 M solution of lithium bιs(tπfluoromethylsulfonyl) imide in sulfolane saturated with sulfur, to which was added 10 % by weight of hexachlorocyclopentadiene Example 7

Cells were prepared and discharged by the method of Comparative Example 2 except that the electrolyte was a 0.5 M solution of AICI₃ in propylene carbonate saturated with sulfur. This corresponds to about 5.3%₀ by weight of AICI₃ in the non-aqueous electrolyte prior to the saturation with sulfur.

Example 8

Cells were prepared and discharged by the method of Comparative Example 2 except that the electrolyte was a 0.5 M solution of AICI₃ in propylene carbonate saturated with sulfur, to which was added 10 % by weight of CC1₄.

Example 9

Cells were prepared and discharged by the method of Comparative Example 2 except that the electrolyte was a 0.5 M solution of AICI₃ in propylene carbonate saturated with sulfur, to which was added 10 % by weight of hexachlorocyclopentadiene.

Comparative Example 3

Cells were prepared and discharged by the method of Comparative Example 2 except that the electrolyte was a 0.5 M solution of LiPF₆ in propylene carbonate saturated with sulfur.

Example 10

Cells were prepared and discharged by the method of Comparative Example 2 except that the electrolyte was a 0.5 M solution of LiPF₆ in propylene carbonate saturated with sulfur, to which was added 10 % by weight of CC1 .

Example 1 1

Cells were prepared and discharged by the method of Comparative Example 2 except that the electrolyte was a 0.5 M solution of LiPF₆ in propylene carbonate saturated with sulfur, to which was added 10 % by weight of hexachlorocyclopentadiene.

The discharge voltages ofthe cells of Examples 5-11 containing voltage-enhancing additives of this invention and Comparative Examples 2 and 3 are shown in Table 2.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made without departing from the spirit and scope thereof.

Claims

A primary electrochemical cell compπsing

(a) a lithium anode, (b) a cathode comprising an electroactive sulfur-contammg matenal, and

(c) a non-aqueous electrolyte interposed between said anode and said cathode, wherein said electrolyte comprises

(l) one or more non-aqueous electrolyte solvents, and (π) one or more voltage-enhancing reactive components, wherein said one or more voltage-enhancmg reactive components are non- electroactive

The cell of claim 1, wherein said one or more voltage-enhancing reactive components are selected from the group consisting of organic halides, inorganic halides, and phosphorus chalcogenides

The cell of claim 2, wherein said organic halide is ofthe formula

R,X wherein R_f is CF₃(CF₂)_n, where n is an integer from 0 to 10, and

X is selected from the group consisting of F, Cl, Br, I, SO₂F, SO₂Cl, SO₂R₁, SOR,, CO₂R,, OR_f, SO₂R,', SORf¹, CO₂RI ' , and OR,¹ , wherein R,¹ is (CF₂)_PY, where p is an integer from 1 to 10, and Y is selected from the group consisting of F, Cl, Br, I, SO₂F, SO₂Cl, SO₂R,, SOR,, CO₂R,, and OR_f

The cell of claim 2, wherein said organic halide is selected from the group consisting of perchloroalkanes, perchloroalkenes, and perchlorocycloalkenes

The cell of claim 2, wherein said inorganic halide is selected from the group consisting of A1F₃, A1C1₃, BF₃, BC1₃, MgCl₂, PF₅, PC1₃, PC1₅, SιCl₄, TιCl₄, SF₄, and SF₆

6. The cell of claim 2, wherein said phosphorus chalcogenide is selected from the group consisting of P₂S₅, P₄S]₀, P₂O₅, P₄Oιo, and phosphorus oxysulfides.

7. The cell of claim 1, wherein said one or more non-aqueous electrolyte solvents are selected from the group consisting of ethers, cyclic ethers, polyethers, carbonates, esters, sulfones, sulfites, and sulfolanes.

8. The cell of claim 1 , wherein one or more of said one or more voltage-enhancing reactive components is a non-aqueous electrolyte solvent.

9. The cell of claim 1, wherein said electrolyte comprises one or more lithium salts.

10. The cell of claim 9, wherein said one or more lithium salts are selected from the group consisting of LiBr, Lil, LiSCN, LiBF , LiPF₆, LiAsF<„ LiSO₃CF₃, LiN(SO₂CF₃)_2, LiC(SO₂CF₃)₃, (LiS_x)₂R, and Li₂S_x, where x is an integer from 1 to

20, z is an integer from 1 to 3, and R is an organic group.

11. The cell of claim 1, wherein said electrolyte comprises Li₂S_x, where x is an integer from 1 to 20.

12. The cell of claim 1 , wherein said electroactive sulfur-containing material comprises elemental sulfur.

13. The cell of claim 1, wherein said electroactive sulfur-containing material, in its oxidized state, comprises one or more polysulfide moieties, -S_m-, where m is an integer equal to or greater than 3.

14. The cell of claim 1, wherein said electroactive sulfur-containing material, in its oxidized state, comprises one or more polysulfide moieties, -S_m\ where m is an integer equal to or greater than 3.

15. The cell of claim 1, wherein said electroactive sulfur-containing material, in its oxidized state, comprises one or more polysulfide moieties, S_m ²\ where m is an integer equal to or greater than 3.

16. The cell of claim 1, wherein said electroactive sulfur-containing material, in its oxidized state, is ofthe general formula C(S_x) T_n

wherein x ranges from greater than 2.5 to about 50, and n is an integer equal to or greater than to 2.

17. The cell of claim 1, wherein said electroactive sulfur-containing material comprises greater than 50%o by weight of sulfur.

18. The cell of claim 1, wherein said electroactive sulfur-containing material comprises greater than 75% by weight of sulfur.

19. The cell of claim 1, wherein said electroactive sulfur-containing material comprises greater than 90% by weight of sulfur.

20. The cell of claim 1, wherein said lithium anode is selected from the group consisting of lithium metal, lithium-aluminum alloys, lithium-tin alloys, lithium- intercalated carbons, and lithium-intercalated graphites.

21. The cell of claim 1, wherein said cell has a voltage greater than 2.5 V.

22. The cell of claim 1, wherein said cell has a voltage greater than 2.8 V.

23. The cell of claim 1, wherein said cell has a voltage greater than 3.0 V.

24. The cell of claim 1, wherein said cell has an energy density greater than 1000 Wh/Kg.

25. The cell of claim 1, wherein said cell has an energy density greater than 1200 Wh/Kg.

26. The cell of claim 1, wherein said cell has an energy density greater than 1500 Wh Kg.

27. A method of making a lithium primary electrochemical cell comprising the steps of:

(a) providing a lithium anode; (b) providing a cathode comprising an electroactive sulfur-containing material; and

(c) interposing a non-aqueous electrolyte between said anode and said cathode, wherein said electrolyte comprises:

(i) one or more non-aqueous solvents; and (ii) one or more voltage-enhancing reactive components; wherein said one or more voltage-enhancing reactive components are non- electroactive.

28. The method of claim 27, wherein said one or more voltage-enhancing reactive components are selected from the group consisting of organic halides, inorganic halides, and phosphorus chalcogenides.

29. The method of claim 27. wherein one or more of said one or more voltage- enhancing reactive components is a non-aqueous electrolyte solvent.