Methods of fabricating rechargeable positive electrodes

Disclosed are methods of making solid-phase active-sulfur-based composite electrodes. The method begins with a step of combining the electrode components (including an electrochemically active material, an electronic conductor, and an ionic conductor) in a slurry. Next, the slurry is homogenized such that the electrode components are well mixed and free of agglomerates. Very soon thereafter, before the electrode components have settled or separated to any significant degree, the slurry is coated on a substrate to form a thin film. Finally, the coated film is dried to form the electrode in such a manner that the electrode components do not significantly redistribute.

FIELD OF USE 
This invention relates generally to positive electrodes characterized by 
active-sulfur. The electrodes are preferably rechargeable, and in some 
preferred embodiments are constructed in a thin-film format. Various 
negative electrodes, such as, alkali metal, alkaline earth metal, 
transition metal, and carbon insertion electrodes, among others, can be 
coupled with the positive electrode to provide battery cells, preferably 
having high specific energy (Wh/kg) and energy density (WM). 
BACKGROUND OF THE INVENTION 
The rapid proliferation of portable electronic devices in the international 
marketplace has led to a corresponding increase in the demand for advanced 
secondary batteries. The miniaturization of such devices as, for example, 
cellular phones, laptop computers, etc., has naturally fueled the desire 
for rechargeable batteries having high specific energies (light weight). 
At the same time, mounting concerns regarding the environmental impact of 
throwaway technologies, has caused a discernible shift away from primary 
batteries and towards rechargeable systems. 
In addition, heightened awareness concerning toxic waste has motivated, in 
part, efforts to replace toxic cadmium electrodes in nickel/cadmium 
batteries with the more benign hydrogen storage electrodes in nickel/metal 
hydride cells. For the above reasons, there is a strong market potential 
for environmentally benign secondary battery technologies. 
Secondary batteries are in widespread use in modern society, particularly 
in applications where large amounts of energy are not required. However, 
it is desirable to use batteries in applications requiring considerable 
power, and much effort has been expended in developing batteries suitable 
for high specific energy, medium power applications, such as, for electric 
vehicles and load leveling. Of course, such batteries are also suitable 
for use in lower power applications such as cameras or portable recording 
devices. 
At this time, the most common secondary batteries are probably the 
lead-acid batteries used in automobiles. Those batteries have the 
advantage of being capable of operating for many charge cycles without 
significant loss of performance. However, such batteries have a low energy 
to weight ratio. Similar limitations are found in most other systems, such 
as Ni-Cd and nickel metal hydride systems. 
Among the factors leading to the successful development of high specific 
energy batteries, is the fundamental need for high cell voltage and low 
equivalent weight electrode materials. Electrode materials must also 
fulfill the basic electrochemical requirements of sufficient electronic 
and ionic conductivity, high reversibility of the oxidation/reduction 
reaction, as well as excellent thermal and chemical stability within the 
temperature range for a particular application. Importantly, the electrode 
materials must be reasonably inexpensive, widely available, non-toxic, and 
easy to process. 
Thus, a smaller, lighter, cheaper, non-toxic battery is sought for the next 
generation of batteries. The low equivalent weight of lithium renders it 
attractive as a battery electrode component for improving weight ratios. 
Lithium provides also greater energy per volume than do the traditional 
battery standards, nickel and cadmium. 
The low equivalent weight and low cost of sulfur and its nontoxicity 
renders it also an attractive candidate battery component. Successful 
lithium/organosulfur battery cells are known. (See, De Jonghe et al., U.S. 
Pat. Nos. 4,833,048 and 4,917,974; and Visco et al., U.S. Pat. No. 
5,162,175.) 
However, employing a positive electrode based on elemental sulfur in an 
alkali metal-sulfur battery system has been considered problematic. 
Although theoretically the reduction of sulfur to an alkali metal sulfide 
confers a large specific energy, sulfur is known to be an excellent 
insulator, and problems using it as an electrode have been noted. Such 
problems referred to by those in the art include the necessity of 
adjoining the sulfur to an inert electronic conductor, very low 
percentages of utilization of the bulk material, poor reversibility, and 
the formation of an insulating sulfur film on the carbon particles and 
current collector surface that electronically isolates the rest of the 
electrode components. (DeGott, P., "Polymere Carbone-Soufre Synth ese et 
Propri etes Electrochimiques," Doctoral Thesis at the Institut National 
Polytechnique de Grenoble (date of defense of thesis: 19 Jun. 1986) at 
page 117.) 
Similarly, Rauh et al., "A Lithium/Dissolved Sulfur Battery with an Organic 
Electrolyte," J., Electrochem. Soc., 126 (4): 523 (April 1979) state at 
page 523: "Both S.sub.8 and its ultimate discharge product, Li.sub.2 S, 
are electrical insulators. Thus it is likely that insulation of the 
positive electrode material . . . led to the poor results for Li/S cells." 
Further, Peramunage and Licht, "A Solid Sulfur Cathode for Aqueous 
Batteries," Science, 261: 1029 (20 Aug. 1993) state at page 1030: "At low 
(room) temperatures, elemental sulfur is a highly insoluble, insulating 
solid and is not expected to be a useful positive electrode material." 
However, Peramunage and Licht found that interfacing sulfur with an 
aqueous sulfur-saturated polysulfide solution converts it from an 
insulator to an ionic conductor. 
The use of sulfur and/or polysulfide electrodes in non-aqueous or aqueous 
liquid-electrolyte lithium batteries (that is, in liquid formats) is 
known. For example, Peled and Yamin, U.S. Pat. No. 4,410,609, describe the 
use of a polysulfide positive electrode Li.sub.2 S.sub.x made by the 
direct reaction of Li and S in tetrahydrofuran (THF). Poor cycling 
efficiency typically occurs in such a cell because of the use of a liquid 
electrolyte with lithium metal foil, and the Peled and Yamin patent 
describes the system for primary batteries. Rauh et al., "Rechargeable 
Lithium-Sulfur Battery"(Extended Abstract), J. Power Sources, 26: 269 
(1989) also notes the poor cycling efficiency of such cells and states at 
page 270 that "most cells failed as a result of lithium depletion." 
Other references to lithium-sulfur battery systems in liquid formats 
include the following: Yamin et al., "Lithium Sulfur Battery,"J. 
Electrochem. Soc., 135(5): 1045 (May 1988); Yamin and Peled, 
"Electrochemistry of a Nonaqueous Lithium/Sulfur Cell," J.Power Sources, 
9: 281 (1983); Peled et al., "Lithium-Sulfur Battery: Evaluation of 
Dioxolane-Based Electrolytes,"J. Electrochem. Soc., 136(6): 1621 (June 
1989); Bennett et al., U.S. Pat. No. 4,469,761; Farrington and Roth, U.S. 
Pat. No. 3,953,231; Nole and Moss, U.S. Pat. No. 3,532,543; Lauck, H., 
U.S. Pat. Nos. 3,915,743 and 3,907,591; Societe des Accumulateurs Fixes et 
de Traction, "Lithium-sulfur battery," Chem. Abstracts, 66: Abstract No. 
111055d at page 10360 (1967); and Lauck, H. "Electric storage battery with 
negative lithium electrode and positive sulfur electrode," Chem. 
Abstracts, 80: Abstract No. 9855 at pages 466-467 (1974).) 
DeGott, Supra, notes at page 118 that alkali metal-sulfur battery systems 
have been studied in different formats, and then presents the problems 
with each of the studied formats. For example, he notes that an "all 
liquid" system had been rapidly abandoned for a number of reasons 
including among others, problems of corrosiveness of liquid lithium and 
sulfur, of lithium dissolving into the electrolyte provoking 
self-discharge of the system, and that lithium sulfide forming in the 
positive (electrode) reacts with the sulfur to give polysulfides Li.sub.2 
S.sub.x that are soluble in the electrolyte. 
In regard to alkali metal-sulfur systems wherein the electrodes are molten 
or dissolved, and the electrolyte is solid, which function in exemplary 
temperature ranges of 130.degree. C. to 180.degree. C. and 300.degree. C. 
to 350.degree. C., DeGott states at page 118 that such batteries have 
problems, such as, progressive diminution of the cell's capacity, 
appearance of electronic conductivity in the electrolyte, and problems of 
safety and corrosion. DeGott then lists problems encountered with alkali 
metal-sulfur battery systems wherein the electrodes are solid and the 
electrolyte is an organic liquid, and by extension wherein the negative 
electrode is solid, the electrolyte is solid, and the positive electrode 
is liquid. Such problems include incomplete reduction of sulfur, mediocre 
reversibility, weak maximum specific power (performance limited to slow 
discharge regimes), destruction of the passivating layer of Li.sub.2 S as 
a result of its reaction with dissolved sulfur leading to the formation of 
soluble polysulfides, and problems with the stability of the solvent in 
the presence of lithium. 
DeGott also describes on page 117 a fundamental barrier to good 
reversibility as follows. As alkali metal sulfides are ionic conductors, 
they permit, to the degree that a current collector is adjacent to sulfur, 
the propagation of a reduction reaction. By contrast, their reoxidation 
leads to the formation of an insulating sulfur layer on the positive 
electrode that ionic ally insulates the rest of the composite, resulting 
in poor reversibility. 
DeGott concludes on page 119 that it is clear that whatever format is 
adopted for an alkali metal-sulfur battery system that the insulating 
character of sulfur is a major obstacle that is difficult to overcome. He 
then describes preliminary electrochemical experiments with a composite 
sulfur electrode prepared from a slurry. The slurry was prepared by mixing 
the following components in acetonitrile: 46% sulfur; 16% acetylene black; 
and 38% (PEO).sub.8 /LiClO.sub.4 (polyethylene oxide/lithium perchlorate). 
The resulting slurry was then deposited on a stainless steel substrate by 
"capillary action." From those preliminary experiments, DeGott concludes 
on page 128 that it is clear that, even when optimizing the efficiency of 
the composite electrode (that is, by multiplying the triple point 
contacts) that elemental sulfur cannot be considered to constitute an 
electrode for a secondary battery, in an "all solid" format. 
Present solid-state lithium secondary battery systems are limited to a 
specific energy of about 120 Wh/kg. It would be highly desirable to have a 
battery system characterized by higher specific energy values. 
It would be even more desirable if solid-state batteries having practical 
specific energy values greater than about 150 Wh/kg could operate at room 
temperature. It would be additionally advantageous if solid-state 
batteries having high specific energy and operation at room temperature 
could be reliably fabricated into units with reproducible performance 
values. 
In lithium cells wherein a liquid electrolyte is used, leakage of the 
electrolyte can leave lithium exposed to the air, where it rapidly reacts 
with water vapor and oxygen. Substantial casing can prevent such reactions 
and protect users and the environment from exposure to hazardous, 
corrosive, flammable or toxic solvents but adds unwanted weight to the 
battery. A solid-state battery would greatly reduce such problems of 
electrolyte leakage and exposure of lithium, and would allow reducing the 
weight of the battery. 
Furthermore, a battery formulation that overcomes the problem of lithium 
depletion described in the prior art, for example, Rauh et al., supra, 
would have many advantages. 
In summary, disadvantages in currently available metal-sulfur battery 
systems include poor cycling efficiency, poor reversibility, lithium 
depletion, or operating temperatures above 200.degree. C., among other 
problems. Practitioners in the battery art have long sought a solid-state 
or gel-state metal-sulfur battery system that would overcome these 
limitations. 
SUMMARY OF THE INVENTION 
This invention provides a positive electrode for a battery cell that has 
low equivalent weight and high cell voltage and consequently a high 
specific energy, and operates in a wide range of temperatures including 
ambient and sub-ambient temperatures. An exemplary operating temperature 
range for the batteries of this invention is from -40.degree. C. to 
145.degree. C. The batteries of this invention are preferably 
rechargeable. Thin film type battery cells are preferred embodiments. 
The positive electrode of this invention comprises an active-sulfur-based 
material having a relatively low equivalent weight. Said electrode is a 
composite comprising, in the theoretically fully charged state, elemental 
sulfur, preferably an ionically conductive material, and an electronically 
conductive material. Upon discharge, the active-sulfur of the positive 
electrode reacts with the metal of the negative electrode, and metal 
sulfides and polysulfides form. For example, where M is the metal of the 
negative electrode, the overall cell reaction can be described as follows: 
EQU x/z M+S=M.sub.x/z S 
wherein M is any metal that can function as an active component in a 
negative electrode in a battery cell wherein active-sulfur is the active 
component of the positive electrode; x=0 through x=2;z=the valence of the 
metal; and S is sulfur. 
M is preferably selected from the group consisting of alkali metals, 
alkaline earth metals, and transition metals. M is more preferably 
selected from the group consisting of alkali metals, and still more 
preferably lithium or sodium. M is most preferably lithium. 
More specifically, for example, in a preferred embodiment of this invention 
wherein the negative electrode contains lithium, the overall cell reaction 
wherein z=1 can be described as follows: 
EQU xLi+S=Li.sub.x S. 
When x=2,100% of the theoretical specific energy of the system has been 
released. 
Upon discharge, the positive electrode becomes a combination of sulfur, 
metal sulfides and polysulfides, and during the discharging process the 
proportions of those sulfur-containing components will change according to 
the state of charge. The charge/discharge process in the positive 
electrode is reversible. Similarly, upon recharging, the percentages of 
the sulfur-containing ingredient will vary during the process. 
The positive electrode is thus made from an electrode composition 
comprising active-sulfur, an electronically conductive material intermixed 
with the activesulfur in a manner that permits electrons to move between 
the active-sulfur and the electronically conductive material, and an 
ionically conductive material intermixed with the active-sulfur in a 
manner that permits ions to move between the ionically conductive material 
and the sulfur. 
The ionically conductive material of said composite positive electrode is 
preferably a polymeric electrolyte, more preferably a polyalkylene oxide, 
and further, preferably polyethylene oxide in which an appropriate salt 
may be added. Additional ionically conductive materials for use in the 
positive electrode include the components described below in the 
solid-state and gel-state electrolyte separator. 
Exemplary electronically conductive materials of the composite positive 
electrode include carbon black, electronically conductive compounds with 
conjugated carbon-carbon and/or carbon-nitrogen double bonds, for example 
but not limited to, electronically conductive polymers, such as, 
polyaniline, polythiophene, polyacetylene, polypyrrole, and combinations 
of such electronically conductive materials. The electronically conductive 
materials of the positive electrode may also have electrocatalytic 
activity. 
The composite sulfur-based positive electrode may further optionally 
comprise performance enhancing additives, such as, binders; 
electrocatalysts, for example, phthalocyanines, metallocenes, brilliant 
yellow (Reg. No. 3051-11-4 from Aldrich Catalog Handbook of Fine 
Chemicals; Aldrich Chemical Company, Inc., 1001 West Saint Paul Avenue, 
Milwaukee, Wis. 53233 (USA)) among other electrocatalysts; surfactants; 
dispersants (for example, to improve the homogeneity of the electrode's 
ingredients); and protective layer forming additives (for example, to 
protect a lithium negative electrode), such as, organosulfur compounds, 
phosphates, iodides, iodine, metal sulfides, nitrides, and fluorides, for 
example LiI, PbS, and HF. 
The range of active-sulfur in such electrodes in the theoretically fully 
charged state is from 20% to 80% by weight. Said active-sulfur-based 
composite electrode is preferably processed such that the component 
particles are homogeneously distributed, and segregation and/or 
agglomeration of the component particles is avoided. 
A metal-sulfur battery system constructed with said active-sulfur-based 
composite positive electrode of this invention should have at least 5%, 
and more preferably at least 10% availability of the active-sulfur. That 
availability corresponds to a minimum of 168 mAh per gram of sulfur 
included in the positive electrode. This is based on the theoretical value 
of 1675 mAh/gm of sulfur at 100% availability. 
The electrolyte separator used in combination with the positive electrodes 
of this invention functions as a separator for the electrodes and as a 
transport medium for the metal ions. Any electronically insulating and 
ionically conductive material which is electrochemically stable may be 
used. For example, it has been shown that polymeric, glass and/or ceramic 
materials are appropriate as electrolyte separators, as well as other 
materials known to those of skill in the art, such as, porous membranes 
and composites of such materials. Preferably, however, the solid-state 
electrolyte separator is any suitable ceramic, glass, or polymer 
electrolyte such as, polyethers, polyimines, polythioethers, 
polyphosphazenes, polymer blends, and the like, in which an appropriate 
electrolyte salt may be added. In the solid-state, the electrolyte 
separator may contain an aprotic organic liquid wherein said liquid 
constitutes less than 20% (weight percentage) of the total weight of the 
electrolyte separator. 
In the gel-state, the electrolyte separator contains at least 20% (weight 
percentage) of an aprotic organic liquid wherein the liquid is immobilized 
by the inclusion of a gelling agent. Any gelling agent, for example, 
polyacrylonitrile, PVDF, or PEO, can be used. 
The liquid electrolyte for the liquid format batteries using the positive 
electrode of this invention, is also preferably an aprotic organic liquid. 
The liquid format battery cells constructed using the positive electrodes 
of this invention would preferably further comprise a separator which acts 
as an inert physical barrier within the liquid electrolyte. Exemplary of 
such separators include glass, plastic, ceramic, polymeric materials, and 
porous membranes thereof among other separators known to those in the art. 
Solid-state and gel-state positive electrodes of this invention can be used 
in solid-state or liquid format batteries, depending on the specific 
format of the electrolyte separator and negative electrode. Regardless of 
the format of the batteries using the positive electrode of this 
invention, the negative electrode can comprise any metal, any mixture of 
metals, carbon or metal/carbon material capable of functioning as a 
negative electrode in combination with the active-sulfur-based composite 
positive electrode of this invention. Accordingly, negative electrodes 
comprising any of the alkali or alkaline earth metals or transition metals 
for example, (the polyether electrolytes are known to transport divalent 
ions such as Zn.sup.++) in combination with the positive electrode of this 
invention are within the ambit of the invention, and particularly alloys 
containing lithium and/or sodium. 
Preferred materials for said negative electrodes include Na, Li and 
mixtures of Na or Li with one or more additional alkali metals and/or 
alkaline earth metals. The surface of such negative electrodes can be 
modified to include a protective layer, such as that produced on the 
negative electrode by the action of additives, including organosulfur 
compounds, phosphates, iodides, nitrides, and fluorides, and/or an inert 
physical barrier conductive to the metal ions from the negative electrode, 
for example, lithium ions transport in lithium phosphate, or silicate 
glasses, or a combination of both. 
Also preferred materials for said negative electrodes include carbon, 
carbon inserted with lithium or sodium, and mixtures of carbon with 
lithium or sodium. Here, the negative electrode is preferably carbon, 
carbon inserted with lithium or sodium, and/or a mixture of carbon with 
lithium or sodium. When the negative electrode is carbon, the positive 
electrode is in the fully discharged state, comprising lithium or sodium 
sulfides and polysulfides. Particularly preferred negative electrodes for 
batteries are lithium inserted within highly disordered carbons, such as, 
poly p-phenylene based carbon, graphite intercalation compounds, and 
Li.sub.y C.sub.6 wherein y=0.3 to 2, for example, LiC.sub.6, Li.sub.2 
C.sub.6 and LiC.sub.12. When the negative electrode is carbon, the cells 
are preferably assembled with the positive electrode in the fully 
discharged state comprising lithium or sodium sulfides and/or 
polysulfides. The use of negative electrodes of the carbon, carbon 
inserted with lithium or sodium, and mixtures of carbon with lithium or 
sodium with the solid-state and gel-state positive electrodes of this 
invention are especially advantageous when the battery is in the liquid 
format. 
In another aspect, the present invention provides methods of forming an 
active-sulfur-containing electrode. Such methods may be characterized as 
including the following steps: (a) combining active-sulfur, an electronic 
conductor, and an ionic conductor to form a mixture; (b) homogenizing the 
mixture to form a homogeneous mixture; and (c) forming the 
active-sulfur-containing electrode from the homogeneous mixture. The 
method is conducted in a such a manner that the resulting 
active-sulfur-containing electrode has at least about 5% (and more 
preferably at least about 10%) of its active-sulfur available for 
electrochemical reaction. In many embodiments, the method will involve a 
step of forming a slurry in order to facilitate formation the electrode. A 
thin layer of such slurry is then deposited on a substrate and allowed to 
dry. In other embodiments, no slurry is formed and, instead, the step of 
homogenizing comprises homogenizing a solid phase mixture containing the 
active-sulfur, the electronic conductor, and the ionic conductor. The 
resulting homogeneous mixture may then be converted to an electrode by 
such processes as extrusion, calendaring, electrostatic deposition, or a 
process analogous to the solid phase rubber processing methods 
conventionally used in that art. 
In preferred embodiments, the step of forming the active-sulfur-containing 
electrode involves a step of depositing a layer of the homogeneous mixture 
on a substrate by a technique that does not rely on capillary action. If 
the homogeneous mixture is provided as a slurry, it is believed that 
deposition without capillary action helps to ensure that the resulting 
film will not segregate and therefore provide good contact between the 
active-sulfur, the ionic conductor, and the electronic conductor, thus 
allowing greater than 5% utilization of the active-sulfur. 
When a slurry is employed to prepare the electrode, a further step of 
drying must be employed to form the electrode. The slurry may be dried on 
either a non-adhesive substrate or on a current collector. In the latter 
case, the electrode is essentially completely fabricated upon drying. In 
the former case, the dried electrode must be first removed from the 
nonadhesive substrate, and then affixed to a current collector such that 
the active-sulfur-containing electrode is in electrical contact with the 
current collector. 
These and other features of the invention will further described and 
exemplified in the drawings and detailed description below.

DETAILED DESCRIPTION 
The instant invention provides a positive electrode for solid-state and 
liquid format battery systems, wherein the positive electrode is based on 
active-sulfur which provides high specific energy and power, exceeding 
that of highly developed systems now known and in use. Solid-state format 
battery cell means all the components of the battery are either 
solid-state or gel-state. It further means that no component is in a 
liquid state. The equivalent weight of the active-sulfur used in the redox 
reactions within the battery cells of this invention is 16 
grams/equivalent (with a lithium metal as the negative electrode, 
active-sulfur in its theoretically fully discharged state is Li.sub.2 S), 
leading to a theoretical specific energy of 2800 watthours per kilogram 
(Wh/kg) for a lithium cell having a average OCV of 2.4 volts. Such an 
exceedingly high specific energy is very unusual and highly attractive. 
Further, the batteries containing the positive electrode of this invention 
can operate at room temperature. The battery systems of this invention 
provide energy to weight ratios far in excess of the present demands for 
load leveling and/or electric vehicle applications, and can be reliably 
fabricated into units with reproducible performance values. 
This invention can be incorporated in a battery cell which includes 
solid-state or gel-electrolyte separators. This embodiment excludes the 
problem of a battery cell in the liquid format that may suffer electrolyte 
leakage. For example, in lithium cells wherein a liquid electrolyte is 
used, leakage of the electrolyte can leave lithium exposed to the air, 
where it rapidly reacts with water vapor. Substantive casing can prevent 
such reactions and protects users and the environment from exposure to 
solvents but adds unwanted weight to the battery. Using a solid-state or 
gel-state format battery cells greatly reduces such problems of 
electrolyte leakage and exposure of lithium, and can cut down on the 
weight of the battery. 
Another embodiment concerns battery cells in a liquid format, which have a 
solid active-sulfur-based positive electrode of this invention, and which 
have a solid negative electrode that contains carbon (when in the fully 
discharged state), carbon inserted with lithium or sodium and/or a mixture 
of carbon with lithium or sodium. Such an embodiment can overcome the 
problem of lithium depletion described in the prior art, for example, Rauh 
et al., supra. 
In accordance with this invention, the active-sulfur-based composite 
positive electrode and a battery system constructed with said positive 
electrode are provided. The positive electrodes of this invention are 
preferably reversible, and the metal-active-sulfur battery cells are 
preferably secondary batteries, and more preferably thin film secondary 
batteries. 
The invention relates in one aspect to the positive electrode of battery 
cells wherein both the positive and negative electrodes are solid-state or 
gel-state and the electrolyte separator is either a solid-state or a 
gel-state material (see Definition). In another aspect, as indicated 
above, the positive electrode of this invention is used in a battery cell 
which contains a liquid electrolyte wherein the negative electrode is 
solid or gel-state and contains carbon, carbon inserted with lithium or 
sodium, or mixtures of carbon with lithium or sodium. However, whatever 
the format of the battery cells made with the positive electrodes of this 
invention, said positive electrode comprises elemental sulfur as the 
active component when in the theoretically fully charged state. 
Positive Electrode 
The active-sulfur of the novel positive electrodes of this invention is 
preferably uniformly dispersed in a composite matrix, for example, the 
active-sulfur can be mixed with a polymer electrolyte (ionically 
conductive), preferably a polyalkylene oxide, such as polyethylene oxide 
(PEO) in which an appropriate salt may be added, and an electronically 
conductive material. Furthermore, the ionically conductive material may be 
either solid-state or gel-state format. In most cases it will be necessary 
or desirable to include a suitable polymeric electrolyte, for rapid ion 
transport within the electrode as is done with intercalation materials 
based electrodes. Furthermore, because the active-sulfur is not 
electrically conductive, it is important to disperse some amount of an 
electronically conductive material in the composite electrode. 
Preferred weight percentages of the major components of the 
active-sulfur-based positive electrodes of this invention in a 
theoretically fully charged state are: from 20% to 80% active-sulfur; from 
15% to 75% of the ionically conductive material (which may be gel-state or 
solid-state), such as PEO with salt, and from 5% to 40% of an 
electronically conductive material, such as carbon black, electronically 
conductive polymer, such as polyaniline. More preferably, those 
percentages are: from 30% to 75% of active-sulfur; from 15% to 60% of the 
ionically conductive material; and from 10% to 30% of the electronically 
conductive material. Even more preferable percentages are: from 40% to 60% 
of active-sulfur; from 25% to 45% of the ionically conductive material; 
and from 15% to 25% of the electronically conductive material. Another 
preferred percentage by weight range for the electronically conductive 
material is from 16% to 24%. Methods of Making a Positive Electrode: 
An important feature of this invention is the ability to provide electrodes 
having active material (usually active-sulfur and/or a polydisulfide 
polymer) in intimate contact with both an ionic conductor and an 
electronic conductor. This facilitates ion and electron transport to and 
from the active material to allow nearly complete utilization of the 
active material. To this end, the invention provides a method of producing 
electrodes which ensures that at least about 5% of the active material in 
the resulting electrode will be available for electrochemical reaction. No 
prior method produces electrodes having such high availability of 
active-sulfur. 
A preferred method of making electrodes in accordance with this invention 
is illustrated in the flow chart of FIG. 1. The method begins with a step 
100 of combining the electrode components (including an electrochemically 
active material, an electronic conductor, and an ionic conductor). Next, 
at a step 102, the mixture is homogenized such that the electrode 
components are well mixed and free of agglomerates. Typically, a slurry 
will be formed by combining the electrode components with a liquid at 
either step 100 or step 102. 
After the electrode components are homogenized and in slurry form, the 
slurry is coated on a substrate to form a thin film at a step 104. Best 
results will generally be obtained if the slurry is homogenized 
immediately before the film formation at step 104. This ensures that the 
slurry components have not settled or separated to any significant degree, 
thus providing a uniform film with the desired ratio of electrode 
components. Finally, at a step 106, the coated film is dried to form the 
electrode. The film preferably will be sufficiently thin to allow for 
rapid drying so that the electrode components do not significantly 
redistribute during drying step 106. The actual film thickness will, of 
course, depend upon the amount of liquid used in the slurry. 
The components that are combined at step 100 include at least an 
electrochemically active insulator (e.g., elemental sulfur or a 
polydisulfide), an electronically conductive material, and an ionically 
conductive material. Appropriate ratios of these materials are presented 
above for the resulting electrodes. Generally the same ratios may be 
employed in the mixture used to make the electrodes. The electrochemically 
active insulator is preferably active-sulfur, but any electrochemically 
active insulator or moderately conductive material may benefit from the 
inventive method. The ionic conductor is, as noted, preferably a polymeric 
ion conductor such as a polyalkylene oxide, and more preferably PEO or 
amorphous PEO. To increase the conductivity of the ion conductor, it 
typically will be provided with a salt containing the transported ion 
(e.g., a lithium salt such as lithium trifluoromethanesulfonimide or 
lithium perchlorate as described herein in connection with the 
electrolyte). The electronic conductor is preferably a carbon black or an 
electronically conductive polymer such as a polyaniline, polythiophene, 
polyacetylene, polypyrrole, etc. In an especially preferred embodiment, 
the electrochemically active material is active-sulfur, the ionic 
conductor is PEO (possibly with a small amount of an appropriate salt), 
and the electronic conductor is a carbon black. 
In addition to the three above-mentioned "necessary" electrode components, 
other components that may be added to the mixture include (1) materials to 
catalyze the transfer of electrons from the electronically conductive 
material to the active material, (2) additives to protect an active metal 
electrode surface (e.g., lithium or sodium electrode surfaces) in cells 
that employ such electrodes, (3) dispersants, (4) binders, and (5) 
surfactants. 
Materials that catalyze electron transport between the electrochemically 
active material and the electronic conductor are known in the art and 
include, for example, phthalocyanines, metallocenes, and brilliant yellow. 
Additives to protect an active metal electrode surface include, for 
example, organosulfur compounds such as 
poly-2,5-dimercapto-1,3,4-thiadiazole, phosphates, iodides, iodine, metal 
sulfides, nitrides, and fluorides. These materials are believed to provide 
a protective layer on the metal electrode surface. By casting them in the 
active-sulfur (or other insulator) electrode, small amounts of these 
protective agents will diffuse across the electrolyte to react with the 
metal electrode and provide the protective layer. Further, a dispersant 
(or dispersants) such as Brij or PEG may also be added to the mixture. 
Such materials reduce a tendency to agglomerate exhibited by some of the 
necessary components such as carbon black. Agglomeration, of course, 
degrades the quality of the resulting electrode by preventing thorough 
mixing of the 1.5 components. Other additives are widely used in 
fabricating positive electrodes and are known in the art to have various 
benefits. The use of such additives in formation of electrodes is within 
the scope of this invention. 
As noted, the components of the electrode mixture will typically be 
dispersed in a slurry. Various liquids may be employed in the slurry. 
Typically, but not necessarily, the liquid will not dissolve active-sulfur 
or carbon black. It may, however, dissolve polymeric components such as 
PEO or a polymeric electronic conductor. Preferred liquids evaporate 
quickly so that the resulting film dries completely and before 
redistribution of the components can occur. Examples of acceptable liquids 
for the slurry system include water, acetonitrile, methanol, ethanol, 
tetrahydrofuran, etc. Mixtures of liquid compounds may also be employed. 
In large-scale continuous processes, it may be desirable to use a 
relatively low volatility liquid such as water to facilitate liquid 
recovery for recycling. 
The relative amounts of solid and liquid in the slurry will be governed by 
the viscosity required for subsequent processing. For example, electrodes 
formed by a tape casting apparatus may require a different viscosity 
slurry than electrodes formed with a Mayer rod. The slurry viscosity will, 
of course, be governed by such factors as the composition and amounts the 
slurry components, the slurry temperature, and the particle sizes in the 
slurry. When the mixture includes a soluble ionic conductor such as PEO, 
the slurry ratio is conventionally defined in terms of the amount of 
soluble material to liquid. Amounts of the remaining insoluble components 
are then pegged to the amount of soluble material. For PEO-containing 
electrodes, a preferred range of concentrations is between about 30 and 
200 milliliters of solvent per gram of PEO. 
The exact ordering in which components are added to the slurry is not 
critical to the invention. In fact, as illustrated in examples 18 to 20 
below, various approaches have been found to work with this invention. In 
one embodiment, for example, the soluble components such as PEO and brij 
are first dissolved in the liquid solvent before the insoluble components 
are added. In another exemplary embodiment, all components except 
crystalline PEO are dispersed and dissolved before the crystalline PEO is 
added. The insoluble components may be added to the slurry sequentially or 
in a premixed form (i.e., the solid insolubles are mixed before addition 
to the slurry). 
The process of homogenizing the electrode components (step 102 of FIG. 1 ) 
may take a variety of forms in accordance with the present invention. The 
process may vary depending upon whether electrode fabrication is performed 
batchwise or continuous. For small-scale batch operations, suitable slurry 
homogenization apparatus includes stir bars (preferably cross-type stir 
bars), paint mixers such as rotary blade mixers, paint shakers, and shear 
mixers. Further, any mixing apparatus conventionally used to make "slips" 
in the ceramic processing arts will be sufficient for use with this 
invention. By way of example, some other batch mixing systems employ ball 
milling, tumble mixing, shear mixing, etc. The amount of time required to 
obtain a suitably homogenous mixture can be determined by routine 
experimentation with each of these pieces of mixing equipment. 
Suitably homogenous mixtures are evidenced by high availability of active 
electrode material in the resulting electrode. It has been found that with 
stir bars, homogenization typically requires about 2 days, whereas with 
paint mixers and paint shakers homogenization requires less time (on the 
order of a few hours). In scaling up agitators for suspending solid 
particles, the torque per unit volume generally should be kept constant. 
Even so, blending times typically are significantly longer in larger 
vessels than in smaller ones and this should be factored into any 
scale-up. 
In large-scale and/or continuous electrode fabrication systems, an 
industrial agitator will generally be preferable. Design criteria for such 
systems are well known in the art and are discussed at, for example, pages 
222-264 of McCabe and Smith "Unit Operations of Chemical Engineering" 
Third Edition, McGraw Hill Book Company, New York (1976), which reference 
is incorporated by reference herein for all purposes. Suitable systems 
include turbine agitators and axial-flow or radial-flow impellets in tanks 
or vessels with rounded bottoms. In general, the vessels should not have 
sharp corners or regions where fluid currents cannot easily penetrate. 
Further, the system should be designed to prevent circulatory currents 
which throw solid particles to the outside of the vessel where they move 
downward and concentrate. Circulatory currents can be mitigated by 
employing baffles in the system (e.g., vertical strips perpendicular to 
the wall of the vessel). Shrouded impellers and diffuser rings can also be 
used for this purpose. 
Very soon after the slurry is homogenized, it is deposited as a film on a 
substrate (step 104 of FIG. 1 ). The exact amount of time between 
homogenization and deposition will depend upon the physical character of 
the slurry (viscosity, solids concentration, solids particle sizes, etc.). 
Significant settling and separation of the solids in the slurry is to be 
avoided. Settling can be slowed by employing (a) small particles of low 
density solids, (b) high concentrations of the solids, and/or (c) highly 
viscous liquids. Further the particles of the various solids components of 
the slurry can be chosen so that they all settle at about the same rate, 
thereby avoiding the problem of segregation. To the extent possible, the 
slurry, should be delivered to a substrate immediately after 
homogenization. For example, slip conditioning and supply systems such as 
these provided by EPH Associates, Inc. of Orere, Utah may be used to 
deliver slurry from a homogenizer directly to a substrate. 
Preferably, the step of slurry film deposition does not rely on 
centrifugal, capillary or other forces that tend to exacerbate separation 
of the solid slurry components. Thus, for example, procedures involving 
dipping of a substrate into the slurry generally will not be suitable for 
use in the present invention. 
In accordance with this invention, preferred film formation procedures 
include (1) deposition onto a substrate via a fixed tube or structure 
temporarily defining a chamber above the substrate, (2) spreading via a 
Mayer rod, and (3) spreading via a doctor blade. Deposition via a fixed 
tube is illustrated in FIG. 2 where a tube 122 is placed against a 
substrate 124 with sufficient force to prevent slurry solids from leaking 
outside of deposition region 120. The tube 122 preferably is made from 
inert materials such as glass tube. It should have a smooth bottom so that 
it makes good contact and a reasonably impervious seal with substrate 124. 
An amount of slurry sufficient to cover region 120 is provided through the 
top of tube 122. 
The slurry film also may be applied by spreading. In batch processes, a 
Mayer rod--which is rod of about 1/2 to 1 inch in diameter wound with 
thin wires--may profitably be used to roll out a thin layer of slurry film 
on the substrate. In continuous or batch processes, a doctor blade may be 
employed to deliver a thin layer of slurry to a moving sheet of substrate, 
as explained in more detail below. 
Regardless of how the slurry film is applied, it should have a primary 
dimension, e.g., thickness, that allows for rapid drying. This thickness 
will, of course, depend upon such factors as slurry concentration and 
liquid volatility. In addition, the slurry film thickness should be chosen 
so as to produce electrodes of appropriate thickness for the ultimate 
battery application. For example, low power, high energy applications, 
such as batteries for pacemakers, may use thicker electrodes, e.g., up to 
a few millimeters. In contrast, high power applications, such as batteries 
for power tools or hybrid vehicles should employ thinner electrodes, e.g., 
no more than about 100 .mu.m thick. It should be noted that electrodes of 
appropriate thickness for low power applications may be made by laminating 
two or more thinner electrodes. In this manner, the problem of slow drying 
associated with thick electrodes can be avoided. 
Preferably the substrate on which the slurry is applied is a current 
collector such as a sheet of stainless steel, aluminum, copper, titanium, 
metallized PET, or other conductive material which will not react at 
operating cell conditions. Suitable current collectors may also take the 
form of expanded metals, screens, meshes, foams, etc. as is known in the 
art. In alternative embodiments, the substrate may be a sheet of inert 
material that does not adhere to dried electrode material. One such 
suitable substrate material is Teflon.RTM.. After the electrode film is 
dried, it is peeled away from such substrate and later contacted to a 
current collector such as one of the above-mentioned materials. Contacting 
to the current collector may be accomplished by hot pressing, crimping, 
etc. Alternatively, the current collector can be formed directly on the 
electrode material by a technique such as metal spraying, sputtering, or 
other technique known to those of skill in the art. 
The process of forming an electrode concludes with a drying step (step 106 
of FIG. 1). In batch processes, this is preferably accomplished in two 
steps: evaporation under ambient conditions for 30 seconds to 12 hours, 
followed by drying under vacuum for about 4 to 24 hours at room 
temperature or an elevated temperature. In continuous processes, drying 
may be accomplished by passing a sheet of electrode/substrate through a 
drying chamber such as an IR drier. A typical resulting active-sulfur 
electrode layer will have a density between about 0.0016 and 0.012 grams 
per cm.sup.2. 
A continuous process for preparing sheets of precipitated polymer will now 
be described with reference to FIG. 3. As shown in FIG. 3, a hopper 220 
dispenses a sheet of homogenized slurry 228 of suitable composition as 
described above. The slurry is deposited on a moving substrate sheet 222 
which passes under blade 226 to produce a thin evenly spread layer of 
slurry 230 on substrate 222. The lower tip of blade 226 and the substrate 
222 should be spaced such that slurry layer 230 has a thickness 
facilitating rapid drying as described above. 
The substrate sheet 222--which moved along in the continuous process by a 
roller 232--may be made from a variety of suitable materials including 
flexible Teflon or any other release agent. In addition, the substrate may 
be a material that is intended to be incorporated in the ultimately 
produced electrode. For example, the substrate may include a metal foil, 
metallized PET, or screen that is to form a current collector in the final 
electrode. The substrate 222 with slurry layer 230 is directed into a 
drying apparatus 248 operated at a temperature sufficient to remove much 
of the liquid from the slurry. This apparatus may include one or more 
dryers such as IR dryers, and it may also have a condenser or other system 
(not shown) for recovering evaporated slurry liquid. 
If the substrate sheet 222 is not a current collector, it may be separated 
from the electrode or partially dried electrode after the substrate enters 
drying apparatus 248. The separation can then be accomplished by providing 
separate uptake reels for substrate 222 (outside drying apparatus 248) and 
for the resulting electrode sheet. Of course, if the substrate 222 is a 
current collector or is otherwise intended to be part of the electrode, no 
separation is necessary, and the substrate/electrode laminate is taken up 
on reel 232 as shown. 
In alternative embodiments, the electrode is formed without first preparing 
a slurry. Rather the electrode components--including the 
electrochemically-active insulator, the ion conductor, and the electron 
conductor--are homogenized in a solid state and formed into a sheet as by 
extrusion or calendaring. The solid state homogeneous mixture may also be 
coated onto a substrate by roll coating, blade coating, extrusion coating, 
curtain coating, or a related process. In each case, the solid state 
mixture is caused to flow by application of heat and/or pressure and the 
resulting viscous or viscoelastic mixture is passed though a die, a 
roller, or a blade. In such embodiments, the PEO or other polymeric 
components should be present in concentrations suitable to allow formation 
of a viscous or viscoelastic material under conditions encountered in 
standard polymer processing apparatus. Details of suitable polymer 
processing techniques are found in Middleman, "FUNDAMENTALS OF POLYMER 
PROCESSING", McGraw-Hill, Inc. 1977 which is incorporated herein by 
reference in its entirety and for all purposes. In addition to these 
processing techniques involving flow, alternative techniques within the 
scope of this invention include electrostatic deposition as by processes 
analogous to xerography. Further, dry processes conventionally used in the 
rubber processing arts may be applied to form electrodes in accordance 
with this invention. Because each of the above "dry" techniques do not 
involve a slurry, no drying step is required. Thus, there is less 
opportunity for the solid electrode components to segregate or agglomerate 
after homogenization. 
Electrolyte Separators and Liquid Electrolytes 
The electrolyte separator for solid-state format battery cells 
incorporating the positive electrode of this invention functions as a 
separator for the positive and negative electrodes and as a transport 
medium for the metal ions. As defined above, the material for such an 
electrolyte separator is preferably electronically insulating, ionically 
conductive and electrochemically stable. 
When the battery cell is in a solid-state format, all components are either 
solid-state or gel-state and no component is in the liquid state. 
The aprotic organic liquids used in the electrolyte separators of this 
invention, as well as in the liquid electrolytes of this invention, are 
preferably of relatively low molecular weight, for example, less than 
50,000 MW. Combinations of aprotic organic liquids may be used for the 
electrolyte separators and liquid electrolytes of the battery cells 
incorporating the positive electrode of this invention. 
Preferred aprotic organic liquids of the battery cells incorporating the 
positive electrode of this invention include among other related aprotic 
organic liquids, sulfolane, dimethyl sulfone, dialkyl carbonates, 
tetrahydrofuran (THF), dioxolane, propylene carbonate (PC), ethylene 
carbonate (EC), dimethyl carbonate (DMC), butyrolactone, 
N-methylpyrrolidinone, tetramethylurea, glymes, ethers, crown ethers, 
dimethoxyethane (DME), and combinations of such liquids. 
For the battery cells, incorporating the positive electrode of this 
invention, containing a liquid electrolyte wherein the negative electrode 
is carbon-containing, said liquid is also an aprotic organic liquid as 
described above. Such a format also preferably contains a separator within 
the liquid electrolyte as discussed above. 
An exemplary solid-state electrolyte separator combined with this invention 
is a ceramic or glass electrolyte separator which contains essentially no 
liquid. Polymeric electrolytes, porous membranes, or combinations thereof 
are exemplary of the type of electrolyte separator to which an aprotic 
organic plasticizer liquid could be added according to this invention for 
the formation of a solid-state electrolyte separator containing less than 
20% liquid. 
Preferably the solid-state electrolyte separator is a solid ceramic or 
glass electrolyte and/or solid polymer electrolyte. Said solid-state 
ceramic electrolyte separator preferably comprises a beta alumina-type 
material, Nasicon or Lisicon glass or ceramic. The solid-state electrolyte 
separator may include sodium beta alumina or any suitable polymeric 
electrolyte, such as polyethers, polyimines, polythioethers, 
polyphosphazenes, polymer blends, and the like and mixtures and copolymers 
thereof in which an appropriate electrolyte salt has optionally been 
added. Preferred polyethers are polyalkylene oxides, more preferably, 
polyethylene oxide. 
Exemplary but optional electrolyte salts for the battery cells 
incorporating the positive electrode of this invention include, for 
example, lithium trifluoromethanesulfonimide (LiN(CF.sub.3 
SO.sub.2).sub.2), lithium triflate (LiCF.sub.3 SO.sub.3), lithium 
perchlorate (LiCl.sub.4), LiPF.sub.6, LiBF.sub.4, LiAsF.sub.6, as well as, 
corresponding salts depending on the choice of metal for the negative 
electrode, for example, the corresponding sodium salts. As indicated 
above, the electrolyte salt is optional for the battery cells of this 
invention, in that upon discharge of the battery, the metal sulfides or 
polysulfides formed can act as electrolyte salts, for example, M.sub.x/z S 
wherein x=0 to 2 and z is the valence of the metal. 
Negative electrode 
For solid-state battery cells incorporating the positive electrode of this 
invention, the negative electrode may comprise any metal, any mixture of 
metals, or any carbon or metal/carbon material capable of functioning as 
an active component of a negative electrode in combination with said 
active-sulfur positive electrode. For example, any of the alkali or 
alkaline earth metals or transition metals can be used, and particularly 
mixtures containing lithium and/or sodium. 
Preferred materials for said negative electrode for the solid-state battery 
cell formats include sodium and/or lithium, and mixtures of sodium or 
lithium with one or more additional alkali metals and/or alkaline earth 
metals. Preferred materials for said negative electrode also include 
mixtures of sodium or lithium with one or more elements to form a binary 
or ternary alloy, such as, Na.sub.4 Pb, lithium-silicon and 
lithium-aluminum alloys. 
A particularly preferred metal for a negative electrode is sodium, or at 
least a sodium base alloy (i.e., at least 90% by weight sodium) because of 
its low cost, low equivalent weight and its relatively low melting point 
of 97.8.degree. C. However, other alkali metals such as Li or K, or 
mixtures of same with Na may also be used, as desired, to optimize the 
overall system. 
Also preferred negative electrode materials for the solid-state battery 
cells incorporating the positive electrode of this invention include 
carbon, carbon inserted with lithium or sodium and/or a mixture of carbon 
with sodium or lithium. Exemplary and preferred are Li.sub.y C.sub.6 
(wherein y=0.3 to 2), such as, LiC.sub.6, negative electrodes which 
comprise graphite or petroleum coke, for example, graphite intercalation 
compounds (GICs), and carbon inserted within highly disordered carbons. 
The inserted carbon may also be that wherein some carbon has been alloyed 
with boron, or wherein the carbon has been prepared from low temperature 
pyrolysis (about 750.degree. C.) of carbon or carbon-silicon containing 
polymers such that the carbon product retains some hydrogen or silicon or 
both. (.See, Sato et al., "A Mechanism of Lithium Storage in Disordered 
Carbons," Science, 264: 556 (22 Apr. 1994), which discusses very good 
results with a preferred negative electrode of Li inserted within poly 
p-phenylene-based (PPP-based) carbon.) 
For battery cells using the positive electrode of this invention that are 
in liquid formats, the negative electrode is carbon, carbon inserted with 
lithium or sodium, or mixtures of carbon and lithium or sodium as 
described above in relation to solid-state formats, including the 
preferable versions of such carbon-containing electrodes. For whatever 
format, if the negative electrode contains only carbon, the cell is in the 
theoretically fully discharged state, and the positive electrode comprises 
lithium or sodium sulfides or polysulfides. 
Battery Cells 
The battery cells containing the sulfur-based composite positive electrodes 
of this invention can be constructed according to conventional formats as 
described in the literature. For example, De Jonghe et al., U.S. Pat. No. 
4,833,048 and Visco et al., U.S. Pat. No. 5,162,175. Such conventional 
formats are understood to be herein incorporated by reference. 
The novel battery cells incorporating this invention, preferably secondary 
cells, more preferably thin film secondary cells, may be constructed by 
any of the well-known and conventional methods in the art. The negative 
electrode may be spaced from the positive sulfur electrode, and both 
electrodes may be in material contact with an ionically conductive 
electrolyte separator. Current collectors contact both the positive and 
negative electrodes in a conventional manner and permit an electrical 
current to be drawn by an external circuit. 
Suitable battery constructions may be made according to the known art for 
assembling cell components and cells as desired, and any of the known 
configurations may be fabricated utilizing the invention. The exact 
structures will depend primarily upon the intended use of the battery 
unit. 
A general scheme for the novel battery cells of this invention in a 
solid-state format may include a current collector in contact with the 
negative electrode and a current collector in contact with the positive 
electrode, and a solid-state electrolyte separator sandwiched between the 
negative and positive electrodes. In a typical cell, all of the components 
will be enclosed in an appropriate casing, for example, plastic, with only 
the current collectors extending beyond the casing. Thereby, reactive 
elements, such as sodium or lithium in the negative electrode, as well as 
other cell elements are protected. 
The current collectors can be sheets of conductive material, such as, 
aluminum or stainless steel, which remain substantially unchanged during 
discharge and charge of the cell, and which provide current connections to 
the positive and negative electrodes of the cell. The positive electrode 
film may be attached to the current collector by directly casting onto the 
current collector or by pressing the electrode film onto the current 
collector. Positive electrode mixtures cast directly onto current 
collectors preferably have good adhesion. Positive electrode films can 
also be cast or pressed onto expanded metal sheets. Alternately, metal 
leads can be attached to the positive electrode film by crimpsealing, 
metal spraying, sputtering or other techniques known to those skilled in 
the art. The sulfur-based positive electrode can be pressed together with 
the electrolyte separator sandwiched between the electrodes. In order to 
provide good electrical conductivity between the positive electrode and a 
metal container, an electronically conductive matrix of, for example, 
carbon or aluminum powders or fibers or metal mesh may be used. 
A particularly preferred battery cell comprises a solid lithium or sodium 
electrode, a polymeric electrolyte separator, either solid-state or gel, 
preferably a polyalkylene oxide, such as, polyethylene oxide, and a 
thin-film composite positive electrode containing an elemental sulfur 
electrode (that is in the theoretically fully charged state), and carbon 
black, dispersed in a polymeric electrolyte. Optionally the electrolyte 
separator in such a preferred battery call can comprise an electrolyte 
salt. 
Operating Temperatures 
The operating temperature of the battery cells incorporating the novel 
positive electrode of this invention is preferably 180.degree. C. or 
below. Preferred operating temperature ranges depend upon the application. 
Exemplary preferred operating temperature ranges include from -40.degree. 
C. to 145.degree. C.; from -20.degree. C. to 145.degree. C.; from 
-20.degree. C. to 120.degree. C.; and from 0.degree. C. to 90.degree. C. 
Most preferably for many applications, the cells incorporating this 
invention operate at ambient or above-ambient temperatures. 
Different embodiments of this invention can provide different preferred 
operating temperature ranges. The choice of electrolyte can influence the 
preferred operating temperature ranges for the batteries incorporating the 
positive electrode of this invention. For example, when conventional PEO 
is used the preferred operating range is 60.degree. C. to 120.degree. C.; 
whereas when amorphous PEO (aPEO) is used, the battery can be run at room 
temperature, or in a range of 0.degree. C. to 60.degree. C. 
Gel formats also provide for lower operating temperature ranges. Exemplary 
battery cells using the positive electrode of this invention containing, 
for example, polymeric electrolyte separators with increasingly greater 
percentage of a aprotic organic liquid immobilized by the presence of a 
gelling agent, can provide for increasingly lower operating temperature 
ranges. An exemplary operating temperature range for a solid-state battery 
having gel-state components of this invention would be from about 
-20.degree. C. to about 60.degree. C. 
A battery with a liquid separator and an negative electrode comprising 
carbon, inserted carbon and/or a mixture of carbon and lithium or sodium 
can operate at a preferred temperature range of from -40.degree. C. to 
60.degree. C. 
The high temperature operating range of the battery cells based on the 
positive electrode of this invention can be limited by the melting point 
of either a solid electrode or a solid electrolyte. Thus sodium negative 
electrodes are limited to temperatures below 97.8.degree. C., but sodium 
alloy electrodes, such as Na.sub.4 Pb, can be used in a solid form at well 
over 100.degree. C. 
Specific Energy and Specific Power 
The practical specific energies of the secondary cells utilizing this 
invention are preferably greater than 65 watt-hours per kilogram (Wh/kg), 
more preferably greater than 100 Wh/kg, still more preferably greater than 
150 Wh/kg, even more preferably greater than 200 Wh/kg, and still even 
more preferably greater than 250 Wh/kg. While cells having specific 
energies in the above ranges are preferred for many applications, these 
ranges should not be viewed as limiting the invention. In fact, the cells 
of this invention can be expected to achieve specific energies in excess 
of 850 Wh/kg. Thus, for some applications, a preferred practical specific 
energy range of the batteries incorporating this invention is from about 
100 Wh/kg to about 800 Wh/kg. 
The practical steady-state specific power of the secondary cells utilizing 
this invention are preferably greater than 20 watts per kilogram (W/kg), 
more preferably greater than 50 W/kg, still more preferably greater than 
100 W/kg, even more preferably greater than 150 W/kg, and still even more 
preferably greater than 250 W/kg. It is envisioned that with battery 
construction optimized for power, the steady-state power of this invention 
can exceed 750 W/kg. A preferred practical specific energy range of the 
batteries incorporating this invention is from about 50 W/kg to about 500 
W/kg. The peak and pulse power performances would be many times greater 
than the steady-state power. 
Cells made with lithium negative electrodes, solid-state or gel-state 
electrolyte separators, and positive electrodes made with elemental 
sulfur, polyethylene oxide (or modified polyethylene oxide) and carbon 
particles were constructed to test the performance of the batteries of 
this invention. Examples of these tests will serve to further illustrate 
the invention but are not meant to limit the scope of the invention in any 
way. 
EXAMPLE 1 
Solid-state Cell: Cycling performance at an active-sulfur capacity of 330 
mAh/gm for each recharge cycle.. evaluated at 30.degree. C. 
A positive electrode film was made by mixing 45% (percentage by weight) 
elemental sulfur, 16% carbon black, amorphous polyethylene oxide (aPEO) 
and lithium trifluoromethanesulfonimide (wherein the concentration of the 
electrolyte salt to PEO monomer units (CH.sub.2 CH.sub.2 O) per molecule 
of salt was 49:1), and 5% 2,5-dimercapto-1,3,4-dithiadiazole in a solution 
of acetonitrile (the solvent to PEO ratio being 60:1 by weight). The 
components were stir-mixed for approximately two days until the slurry was 
well mixed and uniform. A thin positive electrode film was cast directly 
onto stainless steel current collectors, and the solvent was allowed to 
evaporate at ambient temperatures. The resulting positive electrode film 
weighed approximately 0.0028 gm per cm.sup.2. 
The polymeric electrolyte separator was made by mixing aPEO with lithium 
trifluoromethanesulfonimide, (the concentration of the electrolyte salt to 
PEO monomer units (CH.sub.2 CH.sub.2 O) per molecule of salt being 39:1) 
in a solution of acetonitrile (the solvent to polyethylene oxide ratio 
being 15:1 by weight). The components were stir-mixed for two hours until 
the solution was uniform. Measured amounts of the separator slurry were 
cast into a retainer onto a release film, and the solvent was allowed to 
evaporate at ambient temperatures. The resulting electrolyte separator 
film weighed approximately 0.0144 gm per cm.sup.2. 
The positive electrode film and polymeric electrolyte separator were 
assembled under ambient conditions, and then vacuum dried overnight to 
remove moisture prior to being transferred into the argon glovebox for 
final cell assembly with a 3 mil (75 micron) thick lithium anode film 
(FMC/Lithco, 449 North Cox Road, Box 3925 Gastonia, N.C. 28054 (USA)). 
A schematic of the cell layers are shown in FIG. 4. Once assembled, the 
cell was compressed at 2 psi and heated at 40.degree. C. for approximately 
6 hours. After heating the layers of lithium, electrolyte separator, and 
the positive electrode were well adhered. 
The cell was then evaluated with a battery tester (Maccor Inc., 2805 West 
40th Street, Tulsa, Okla. 74107 (USA)) inside the glovebox at 30.degree. 
C. That procedure was performed to eliminate any contamination problems of 
the lithium. 
The cell was cycled to a constant capacity corresponding to delivering 330 
mAh per gram of the active-sulfur in the positive electrode film. The 
rates used were 100-20 gA/cm.sup.2 for discharging and 50-10 gA/cm.sup.2 
for charging to cutoff voltages of 1.8 and 3.0 volts, respectively. 
FIG. 5 shows the end of the discharge voltage of the cell after each 
recharge cycle. As evident from the graph, the cell performance is very 
consistent. 
EXAMPLE 2 
Solid-state cell: Total discharge capacity to 900 mAh/gm of active-sulfur 
evaluated at 30.degree. C. 
A cell identical to the one described in Example 1 was discharged to 1.8 
volts at current densities of 100-20 .mu.A/cm.sup.2 at 30.degree. C. to 
determine the total availability of the active-sulfur in the film. The 
resulting discharge curve is seen in FIG. 6. The total capacity delivered 
by this film was in excess of 900 mAh per gram of the active-sulfur, that 
is, a utilization of 54% of the available active-sulfur, wherein 100% 
would be 1675 
EXAMPLE 3 
Solid-state cell having gel-state components: Total discharge capacity to 
900 mAh/gm of active-sulfur evaluated at 30.degree. C. 
A positive electrode film similar to the one described in Example 1 was 
made with a composition of 50% (percentage by weight) elemental sulfur, 
16% carbon black, amorphous polyethylene oxide (aPEO) and lithium 
trifluoromethanesulfonimide (at a 49:1 concentration). 
The electrolyte separator used was a gel made inside the glovebox to avoid 
moisture and oxygen contamination. A starting solution consisting of 10% 
(weight percentage) of lithium trifluoromethanesulfonimide and 90% of 
tetraethylene glycol dimethylether (tetraglyme) was made. Then a solvent 
of 90% tetrahydrofuran (THF) was mixed with 10% of the starting solution. 
5.6% Kynar Flex 2801 (Elf Atochem of North America, Inc., Fluoropolymers 
Department, 2000 Market Street, Philadelphia, Pa. 19103 (USA)), a gelling 
agent (PVDF), was added to the mixture. 
The mixture was stirred for a few minutes and then left standing for 24 
hours so that the components were absorbed into the Kynar,. The mixture 
was stirred again for a few minutes to homogenize the components and then 
heated for 1 hour at 60.degree. C. Electrolyte separator films were cast 
onto a release film, and the THF solvent was allowed to evaporate at 
ambient temperatures. The resulting electrolyte separator film weighed 
approximately 0.0160 gm per cm.sup.2. 
The resulting cell comprising the positive electrode film, the gel-state 
electrolyte separator film, and the lithium negative electrode was tested 
at the same conditions as the cell described in Example 2. The total 
capacity delivered by this film was also in excess of 900 mAh per gram of 
the active-sulfur, that is, a utilization of 54% of the available 
active-sulfur, wherein 100% would be 1675 mAh/gm as shown in FIG. 7. 
EXAMPLE 4 
Solid-state cell: Total discharge capacity to 1500 mAh/gm of sulfur 
evaluated at 90.degree. C. 
A positive electrode film similar to the one described in Example 1 was 
made for use at above ambient temperatures with a composition of 50% 
(weight percentage) elemental sulfur, 16% carbon black, polyethylene oxide 
(900,000 molecular weight) and lithium trifluoromethane-sulfonimide (a 
49:1 concentration). 
The solid-state electrolyte separator used was cast from a slurry of 
900,000 MW PEO in acetonitrile without any additional electrolyte salts. 
The resulting electrolyte separator film weighed approximately 0.0048 gm 
per cm.sup.2. 
The cell was assembled as described in Example 1. Once assembled, the cell 
was compressed at 2 psi and heated at 90.degree. C. for approximately 6 
hours. The cell was tested at 90.degree. C. inside a convection oven 
located in the glovebox. The cell was discharged to 1.8V at rates of 500 
to 100 .mu.A/cm.sup.2. 
The capacity relative to the active-sulfur versus the voltage during 
discharge is shown in FIG. 8. The total capacity delivered by this film 
was also in excess of 1500 mAh per gram of the active-sulfur, that is, a 
utilization of 90% of the available activesulfur, wherein 100% would be 
1675 mAh/gm. 
EXAMPLE 5 
Solid-state cell: Cycling performance at a sulfur capacity of 400 mAh/gm 
for each cycle evaluated at 90.degree. C. 
A positive electrode film similar to the one described in Example 4 was 
made with a composition of 50% (weight percentage) elemental sulfur, 24% 
carbon black, polyethylene oxide (900,000 molecular weight) and lithium 
trifluoromethanesulfonimide (a 49:1 concentration). The electrolyte 
separator is also the same as described in Example 4. The cell was tested 
at 90.degree. C. and cycled to a constant capacity corresponding to 
delivering 400 mAh/gm of the active-sulfur in the positive electrode film. 
The rate used was 500 .mu.A/cm.sup.2 for discharge to 1000-500 
.mu.A/cm.sup.2 for charging at cutoff voltages of 1.8 and 2.6 volts, 
respectively. 
FIG. 9 shows the end of the discharge voltage of the cell after each 
recharge cycle. As evident from the graph, the cell performance is very 
consistent. 
EXAMPLE 6 
Solid-state cell: Cycling performance for each cycle to a cutoff voltage of 
1.8 V evaluated at 90.degree. C. 
A positive electrode film identical to the one described in Example 4 was 
made. The electrolyte separator is also the same as described in Example 
4. The cell was tested at 90.degree. C. and cycled between voltage limits 
between 1.8-2.6 volts. The rates used were 500-100 .mu.A/cm.sup.2 for 
charging. FIG. 10 shows the delivered capacity after each recharge. As 
evident from this graph most recharge cycles delivered above 1000 mAh per 
gram of the active-sulfur used in the cathode film. 
EXAMPLE 7 
Solid-state cell: Peak power performance evaluated at 90.degree. C. 
A positive electrode film similar to the one described in Example 4 was 
made with a composition of 50% (weight percentage) elemental sulfur, 16% 
carbon black, polyethylene oxide (900,000 molecular weight) and lithium 
trifluoromethanesulfonimide (a 49:1 concentration). The electrolyte 
separator is also the same as described in Example 4. The cell was tested 
at 90.degree. C. and pulse discharged for a 30 second duration or to a 
cutoff voltage of 1.2 V. The discharge rates ranged from 0.1-3.5 
mA/cm.sup.2. The pulse power (W/kg) delivered by the cathode film versus 
the current density is shown in FIG. 11. As seen from the plot, an 
extraordinarily high pulse power of 3000 W/kg is capable of being 
attained. 
EXAMPLE 8 
A cell was tested under the conditions described in Example 5 above, except 
that the cell was cycled to a constant capacity corresponding to 
delivering 200 mAh/gm of the active-sulfur in the positive electrode film. 
The electrode was prepared from 50% elemental sulfur, 16% carbon, and the 
balance 900,000 MW PEO. A film of electrode material was formed with a 
Mayer rod onto a current collector. The separator was like the one in 
example 4 with 900,000 MW PEO and formed with a Mayer rod. 
EXAMPLE 9 
A cell was tested under the conditions described in Example 5 above, except 
that the cell was cycled to a constant capacity corresponding to 
delivering 300 mAh/gm of the active-sulfur in the positive electrode film. 
The electrode was prepared from 45% elemental sulfur, 16% carbon, 5% 
2,5-dimercapto-1,3,4-dithiadiazole, and the balance 900,000 MW PEO. A film 
of electrode material was formed with a Mayer rod onto a current 
collector. The separator was like the one in example 4 with 900,000 MW PEO 
and formed with a Mayer rod. 
EXAMPLE 10 
A cell was tested under the conditions described in Example 5 above, except 
that the cell was cycled to a constant capacity corresponding to 
delivering 400 mAh/gm of the active-sulfur in the positive electrode film. 
The electrode was prepared from 45% elemental sulfur, 16% carbon, 5% 
2,5-dimercapto-1,3,4-dithiadiazole, and the balance 900,000 MW PEO. A film 
of electrode material was formed with a Mayer rod onto a current 
collector. The separator was like the one in example 4 with 900,000 MW PEO 
and formed with a Mayer rod. 
EXAMPLE 11 
A cell was tested under the conditions described in Example 5 above, except 
that the cell was cycled to a constant capacity corresponding to 
delivering 600 mAh/gm of the active-sulfur in the positive electrode film. 
The electrode was prepared from 50% elemental sulfur, 24% carbon, 1% PbS, 
and the balance 900,000 MW PEO. A film of electrode material was directly 
cast onto a current collector. The separator was like the one in example 4 
with 900,000 MW PEO and formed with a Mayer rod. 
EXAMPLE 12 
A cell was tested under the conditions described in Example 6 above. The 
electrode was prepared from 50% elemental sulfur, 16% carbon, and the 
balance 900,000 MW PEO. A film of electrode material was formed with a 
Mayer rod onto a current collector. The separator was like the one in 
example 4 but with the addition of 1% PbS. 
EXAMPLE 13 
A cell was tested under the conditions described in Example 6 above. The 
electrode was prepared from 50% elemental sulfur, 24% carbon, and the 
balance 900,000 MW PEO and lithium trifluoromethanesulfonimide (at a 49:1 
weight ratio). A film of electrode material was formed with a Mayer rod 
onto a current collector. The separator was like the one in example 4 with 
900,000 MW PEO and formed with a Mayer rod. 
EXAMPLE 14 
A cell was tested under the conditions described in Example 4 above, but at 
70.degree. C. The electrode was prepared from 50% elemental sulfur, 24% 
carbon, and the balance 900,000 MW PEO and lithium 
trifluoromethanesulfonimide (at a 49:1 weight ratio). A film of electrode 
material was formed with a Mayer rod onto a current collector. The 
separator was like the one in example 4 with 900,000 MW PEO and formed 
with a Mayer rod. 
EXAMPLE 15 
A cell was tested under the conditions described in example 7, but with 
discharge rates ranging from 0.4 to 9 mA/cm.sup.2. The electrode was 
prepared with 50% elemental sulfur, 16% carbon, and the balance 900,000 MW 
PEO. A film of the electrode material was formed with a Mayer rod onto a 
current collector. The separator was like the one in example 4 with 
900,000 MW PEO and formed with a Mayer rod. As seen from the plot, an 
extraordinarily high pulse power of 7400 W/kg of the positive electrode 
can be attained. 
Table 1 presented in FIG. 12a summarizes the performance of the 
representative battery cells of examples 1-7 under the specific testing 
conditions detailed in each example. Table 2 presented in FIG. 12b 
summarizes the performance of the representative battery cells of examples 
8-14 under the specific testing conditions detailed in each example. 
The demonstrated specific energies and specific powers listed above are 
based on the entire composite positive electrode. The electrolyte 
separators and lithium foils used for the laboratory tests were not 
optimized for the final battery. The battery projections are based on 
using 5 .mu.m thick polymeric electrolyte separators, 30 .mu.m thick 
lithium foil and 2.5-5.0 gm thick current collectors. Additionally, there 
is a 10% weight increase allocated for the external casing assuming for 
batteries larger than 1 Amphour. 
Depending on the exact size and configuration of the cell laminate, the 
finished battery performance is approximately 30-70% of the positive 
electrode film performance. For simplicity, 50% has been used for the 
conversion between positive electrode performance and battery projections 
(this is equivalent to 100% battery burden). The calculated density range 
of the battery ranged from 1.0-1.6 gm/cm.sup.3 depending on the specific 
components and configurations. For simplicity, a density of 1.25 
gm/cm.sup.3 is used to calculate the projected energy density (Wh/l). 
As evident from the table, the battery systems containing the positive 
electrode of this invention demonstrate exceptionally high specific 
energies and exceed all now known solid-state intercalation compound-based 
batteries. The cells of this invention also outperform cells which operate 
at much higher temperatures such as the Na/beta"-alumina/Na.sub.2 S.sub.x 
cell (350.degree. C.), LiAl/LiCl, KCl/FeS.sub.2 cell (450.degree. C.). 
It is seen that the invention provides high specific energy and power 
cells, the performance of which exceeds that of highly developed systems 
now known and in use. At the same time, the high energy and power are 
available at room temperature or ambient operation. 
EXAMPLE 16 
This example details one method of making active-sulfur electrodes of this 
invention. Initially, a three inch long piece of stainless steel (Brown 
Metals) was cut off of a four inch wide spool. Both sides of the sheet 
were then abraded with a sanding sponge to remove any insulating coating 
and ensure better electrical contact between the film and the stainless 
steel current collector. The abraded stainless steel current collector was 
wiped with acetone and Kimwipe EX-L until the Kimwipe was clean. A tab for 
electrically connecting the battery was made by cutting a section out of 
the stainless steel. The resulting stainless steel current collector was 
then weighed. 
Next, the current collector was placed on a flat sheet of glass, and a 
standard 13 cm.sup.2 glass casting ring was placed on the center of a 
3".times.3" portion of the steel current collector. Then a syringe was 
filled with a cathode slurry prepared according one of the examples above. 
Quickly 0.5 ml of the slurry was squirted out (or the desired volume to 
obtain the desired capacity per area) onto the area inside the glass ring. 
Before the solvent evaporated, the bead of slurry was spread so as to 
cover the area inside the glass ring with a wet film of even thickness. 
Thereafter, the film was allowed to dry for several hours before removing 
the glass ring from the current collector. An X-acto knife was used to cut 
the film off of the glass ring. The current collector with the film was 
again weighed in order to obtain the weight of the cathode film. 
Electrodes were also prepared on Teledyne stainless steel or aluminum foils 
as described above but without abrading the steel or aluminum since there 
are no insulating coatings as on the Brown Metals steel. 
EXAMPLE 17 
A stainless steel current collector was prepared as described in example 
15. The current collector was then placed on a smooth and flat glass 
sheet, and the middle of the Mayer rod (#RDS 075 is standard now), was 
centered on the edge of the current collector. Several milliliters of 
slurry (as much as necessary so as to not run out of slurry) were poured 
in front of the rod. With one hand holding the substrate in place on the 
glass and the other holding the middle of the rod, the rod was dragged 
across the current collector leaving a wet film. The film was then dried 
and the process was repeated from the other end. The solvent content of 
the slurry was adjusted so that the wet film did not run (too much 
solvent) and did not have a ridged or raked appearance. When the film was 
dried, it was placed on a glass ring (at the center of the 3".times.3" 
current collector), and a circular section was cut along the inside 
circumference of the ring. The excess film outside the circle was then 
scraped off and the weight of the film was determined. 
EXAMPLE 18 
Initially, an aluminum foil current collector prepared as in example 15 was 
placed on a sheet of glass, and taped to the ends of the glass so that it 
did not move while moving the Mayer rod. A Mayer Rod was placed on one end 
of the current collector and enough slurry to cover the desired area of 
current collector was squirted from a syringe in front of the Mayer Rod 
and onto the current collector. When the film was dry, the process was 
repeated as before but processed with a Mayer rod from a different end. 
When the film was dry, unwanted film was scraped off, and the current 
collector was trimmed to the desired area. 
EXAMPLE 19 
The following procedure was employed to prepare a cathode slurry having 
50wt % elemental sulfur, 16 wt % acetylene black, 2 wt % Brij 35, and 32 
wt % 900,000 MW PEO. A 38.times.38 mm stir cross was placed in an 8 oz. 
Quorpac bottle (BWR Scientific, Brisbane, Calif.) with a Teflon lined top. 
To the bottle the following were added: 230 ml of acetonitrile. (Aldrich 
HPLC grade), 6 g of sublimed and ball milled sulfur powder (Aldrich), 1.93 
g of acetylene (Shawinigin) carbon black (Chevron Cedar Bayou Plant), and 
0.24 g of Brij 35 (Fluka). The contents of the bottle were then stirred 
overnight on a magnetic stir plate. The stir-plate power was set to stir 
at as high an RPM as possible without splattering or sucking air. The next 
day, as the slurry was rapidly stirring, 3.85 g of 900,000 MW PEO 
(Aldrich) was added in a stream so as not to form a few large lumps of 
solvent swollen PEO but rather many tiny lumps of solvent swollen PEO. 
During the next two days, the speed of the stir bar was adjusted to 
maintain as high as possible rpms, again without splattering or sucking 
air. After stirring for two nights, the PEO was dissolved and the slurry 
was used to prepare thin films by either ring casting or Mayer rod 
techniques. 
Alternatively, sublimed and precipitated sulfurs were used instead of the 
ball milled sulfur described above, but instead of mixing for two nights, 
about two weeks of stirring were required. If the slurry is mixed for only 
two nights the resulting thin film was found to be porous and lumpy. 
EXAMPLE 20 
The following procedure was employed to prepare a cathode slurry having 50 
wt % elemental sulfur, 24 wt % acetylene black, 2 wt % Brij 35, and the 
balance 900,000 MW PEO:lithium trifluoromethanesulfonimide (20:1) in 
acetonitrile (ml AN:gm PEO, 90:1). A 38.times.38 mm stir cross was placed 
in an 8 oz. Quorpac bottle (BWR Scientific, Brisbane, Calif.) with a 
teflon lined top. To the bottle the following were added: 0.59 g lithium 
trifluoromethanesulfonimide (added in a dry box), 200 ml of acetonitrile 
(Aldrich HPLC grade), 5 g of sublimed and ball milled sulfur powder 
(Aldrich), 2.4 g of acetylene (Shawinigin) carbon black (Chevron Cedar 
Bayou Plant), and 0.2 g of Brij 35 (Fluka). The contents of the bottle 
were then stirred overnight on a magnetic stir plate. The stir-plate power 
was set to stir at as high an RPM as possible without splattering or 
sucking air. The next day, as the slurry was rapidly stirring, 1.8 g of 
900,000 MW PEO (Aldrich) was added in a stream so as not to form a few 
large lumps of solvent swollen PEO but rather many tiny lumps of solvent 
swollen PEO. During the next two days, the speed of the stir bar was 
adjusted to maintain as high as possible rpms, again without splattering 
or sucking air. After stirring for two nights, the PEO was dissolved and 
the slurry was used to prepare thin films by either ring casting or Mayer 
rod techniques. 
EXAMPLE 21 
The following procedure was employed for various slurry compositions 
(identified below). Initially, a glass bottle and a stir bar were washed 
with acetone, and the stir bar was placed in the jar. Then an appropriate 
amount of acetonitrile (depending upon subsequent processing) was added to 
the jar and the bottle was capped. The bottle with its contents was placed 
onto a stir plate operated at sufficient power to create a vortex in the 
acetonitrile. 
Next, PEO was measured and slowly added to the bottle while it was still on 
the stir plate. The PEO was introduced in very small amounts to maximize 
the contact with acetonitrile and promote rapid mixing. If salt was added, 
it was measured and added in the same fashion as the PEO. If there were 
other solubles (brij) to be added, they were also mixed in also at this 
point. All components were mixed until dissolved. Next, all insoluble 
materials including sulfur and carbon were measured and added to the 
mixture. Mixing was conducted for a minimum of two days. 
The slurry combinations employed were as follows: 
(A) 50 wt % elemental sulfur; 24% Carbon (Acetylene Black); 2% brij 35; 24% 
(20 moles PEO 900K to 1 mole lithium trifluoromethanesulfonimide) with 90 
ml acetonitrile per gram of PEO. 
(B) 50 wt % elemental sulfur; 16% Carbon (Acetylene Black); 1% brij 35; 33% 
PEO 900K with 60 ml acrylonitrile per gram of PEO. 
Ranges of components used in preparing various compositions in accordance 
with this example are as follows: 24%-55% wt elemental sulfur; 8%-24% wt 
Carbon (Acetylene Black); 30 ml acrylonitrile per gram PEO to 110 ml 
acetonitrile per gram PEO; and 40, 60, and 90 ml water per gram PEO. Other 
compositions had various additives pegged to elemental sulfur according to 
the following: (1) 5wt % Brilliant Yellow Dye additive with 55% elemental 
sulfur; (2) 5% 2,5-dimercapto-1,3,4-dithiadiazole with 45% elemental 
sulfur; (3) 2 wt % lithium iodide with 48% elemental sulfur; (4) 5 wt % 
iodine with 50% sulfur; (5) 1 wt % PbS with 49% elemental sulfur; and (6) 
5 wt % polyethylene dithiol with 45% elemental sulfur. 
The foregoing describes the instant invention and its presently preferred 
embodiments. Numerous modifications and variations in the practice of this 
invention are expected to occur to those skilled in the art. Such 
modifications and variations are encompassed within the following claims. 
All references cited herein are incorporated by reference.