Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE IN~ENTION
.
1 This invention relates to the art of electrochemical
cells, and more particularly to a new and improved
electrochemical cell includinp, an oxidizable active metal
anode and a mixed soluble depolarizer including a halogen
and/or interhalogen.
In the development of high energy density electro-
chemical cells, much recent work has involved the use
of highly reactive metals such as lithium for the anode
or negative electrode. Work on electrolytes for such
cells has included at least three approaches, one of
which is to employ a high temperature inorganic molten
salt electrolyte. The high temperature of operation
required by this approach, however, necessitates
heating apparatus and insulation which, in turn, give
rise to considerations of weight, complexity and cost.
Also, due to the nature of the materials employed, such
as molten lithium, the cells can have a relatively
short operating life. Another approach is to employ
an organic solvent-based electrolyte or an electrolyte
consisting of an inorganic salt in an organic solvent.
Cells developed according to this approach have the
advantage of operation at room temperature, although
they cannot provide a power density as high as some
cells developed according to the first approach. A
third approach is to provide a solid electrolyte in the
form of a lithium halide ionic compound which has
proved to be highly reliable. There are, however,
2 .
~33049
1 some applications which call for a battery having a
relatively higher current capability.
Summary of the Invention
It is, therefore, a primary object of this invention
to provide a new and improved electrochemical cell of
relatively high energy density having a relatively high
current capability.
It is a further object of this invention to provide
such an electrochemical cell of high reliability.
It is a further object of this invention to provide
such an electrochemical cell having a relatively high
open circuit voltage and current capacity.
It is a further object to provide such an electro-
chemical cell having an oxidizable active anode material
and an electrolyte including a non-aqueous solvent.
The present invention provides an electrochemical
cell of high energy density including a halogen and/or
interhalogen dissolved in a non-aqueous solvent serving
as a soluble depolarizer wherein the halogen and/or
interhalogen also serves as a cosolvent in the cell.
The electrochemical cell comprises an anode of a metal
above hydrogen in the electromotive series, a cathode
of electronically conductive material, and an ionic
conductive electrolytic solution operatively associated
with the anode and cathode, the electrolytic solution
consisting essentially of a first component selected from
--3--
11~304~
1 the group consisting of free halogens, interhalogens and
mixtures thereof dissolved in a second component in the
form of a non-aqueous solvent or a mixture of non-aqueous
solvents. The anode can comprise a metal which is
electrochemically oxidizable to form metal ions in the
cell, for example alkali metals and alkaline earth
metals, and the cathode can comprise electronically
conductive material such as carbon. The non-aqueous
solvent can be an organic solvent which is substantially
inert to the material of the anode and cathode, or the
solvent can be an inorganic solvent which serves as
both a solvent and as a depolarizer in the cell. A
metal salt can be dissolved in the electrolytic solution
to enhance the ionic conduction thereof.
The foregoing and additional advantages and
characterizing features of the present invention will
become clearly apparent upon a reading of the ensuing
detailed description.
Brief Description Of The Drawing Figures
Fig. 1 is a graph including plots of discharge
characteristics for a test cell and a cell according
to one embodiment of the present invention;
Fig. 2 is a graph including plots of discharge
characteristics for a test cell and a cell according
to another embodiment of the present invention;
Fig. 3 is a graph including a plot of the discharge
characteristic of a cell according to another embodiment
of the present invention;
--4--
~330~19
1 Fig. 4 is a graph including plots of discharge characteristics
for a test cell and a prototype cell according to an embodiment
of the present invention;
Fig. 5 is a graph including plots of discharge
characteristics for a prototype cell according to an embodiment
of the present invention for various load resistances;
Fig. 6 is a graph including plots of low rate discharge
characteristics for a prototype cell according to an embodiment
of the present invention for various load resistances;
Fig. 7 is a graph including plots of high temperature
discharge characteristics for a prototype cell according to
an embodiment of the present invention for various load
resistances;
Fig. ~ is a graph including plots of low temperature
discharge characteristics for a prototype cell according
to an embodiment of the present invention for various
load resistances; and
Fig. 9 is a graph including a plot of discharge
characteristics of a cell according to another embodiment of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The electrochemical cell of the present invention com~rises
an anode of a metal above hydrogen in the electromotive
series and which is electrochemically oxidizable to form
metal ions in the cell upon discharge to generate a flow of
electrons in an external electrical circuit connected to the
cell. Preferred metals are al~ali metals and alkaline earth
-
..~
11;~3049
1 metals. Exemplary metals are lithium, sodium, magnesium,
calcium and strontium and alloys and intermetallic compounds
including alkali metals and alkaline earth metals such as
Li-Al alloys and intermetallic compounds, Li-B alloys and
intermetallic compounds, and Li-Si-E alloys and
intermetallic compounds. Other metals can be employed
which, like lithium, can function as the anode metal in the
cell environment. The form of the anode typically is a
thin sheet or foil of the anode metal, and a current
collector having an extending tab or lead is affixed to the
anode sheet or foil.
The electrochemical cell of the present invention further
comprises a cathode of electronically conductive material
which serves as the other electrode of the cell. The electro-
chemical reaction at the cathode involves conversion of ions
which migrate from the anode to the cathode into atomic or
molecular forms. In addition to being electronically
conductive, the material of the cathode may also be electro-
active. Exemplary cathode materials include graphite, and
graphite or carbon bonded on metal screens. Examples of
cathode materials which are electronically conductive and
electro-active include titanium disulfide and lead dioxide.
The form of the cathode typically is a thin layer of carbon
pressed, spread or otherwise applied to a metal screen
current collector.
The electrochemical cell of the present invention further
comprises a non-aqueous, ionic conductive electrolytic solution
operativelyassociated with the anode and the cathode. The
electrolytic solution serves as a medium for migration of ions
113304~9
1 between the anode and cathode during the cell electrochemical
reactions. In accordance with the present invention, the electro-
lytic solution comprises a halogen and/or interhalogen
dissolved in a non-aqueous solvent, the halogen and/or inter-
halogen serving a s a soluble depolarizer in the high
energy density cell. The halogen and/or interhalogen
also can serve as a cosolvent in the electrochemical cell.
The halogen can be iodine, bromine, chlorine or fluorine.
The interhalogen can be ClF, ClF3, lCl, lC13, lBr, lF3
IF5, BrCl, BrF, BrF3, or BrF5. The non-aqueous solvent
may be one of the organic solvents which is substantially
inert to the anode and cathode electrode materials such as
tetrahydrofuran, propylene carbonate, acetonitrile, dimethyl
sulfoxide, dimethyl foramide, dimethyl acetamide and others.
Tne non-aqueous solvent also may be one or a mixture of more
than one of the inorganic solvents which can serve as both a
solvent and a depolarizer such as thionyl chloride, sulfuryl
chloride, selenium oxychloride, chromyl chloride, phosphoryl
chloride, phosphorous sulfur trichloride and others. The
ionic conduction of the non-aqueous electrolytic solution
may be facilitated by dissolving a metal salt in the non-
aqueous halogen solvent. Examples of metal salts are
lithium halides such as LiCl and LiBr and lithium salts
of the LiMxn type such as LiAlC14 Li2A12Cl~0, LiC104,
LiAsF6, LiSbF6, LiSbC16 Li2TiC16 Li2SeC16, Li2BloCl
Li2B12C112 and others
--7--
11;~3~;~4~
1 Thus, the solution of halogen and/or interhalogen, non-
a~ueous solvent and ionic salt if employed serves as the
depolarizer and electrolyte of the cell.
When the mechanical structure or confi~uration of the
cell requires, a separator can be employed to provide physical
separation between the anode and the cathode current collector.
The separator is of electrically insulative material to prevent
an internal electrical short circuit in the cell between the
anode and the cathode current collector. The separator material
also must be chemically unreactive with the materials of the
anode and cathode current collector and both chemically
unreactive with and insoluble in the electrolytic solution.
In addition, the separator material must have a degree of
porosity sufficient to allow flow therethrough of the
electrolytic solution during the electrochemical reaction
of the cell. Illustrative separator materials
include non-woven glass, Teflon, glass fiber material ceramics
and materials commercially available under the designations
Zitex, Celgard and Dexiglas. The form of the separator
typically is a sheet which is placed between the anode and
cathode of the cell in a manner preventing physical contact
between the anode and cathode, and such contact also is
prevented when the combination is rolled or otherwise formed
into a cylindrical configuration.
The electrochemical cell of the present invention
operates in the following manner. When the ionic
conductive electrolytic solution becomes operatively
11;~3049
1 associated with the anode and cathocle of the cell, an
electrical potential difference is cleveloped between
terminals operatively connected to the anode and cathode.
The electrochemical reaction at the anode includes oxidation
to form metal ions during discharge of the cell.
The electrochemical reaction at the cathode involves
conversion of ions which migrate from the anode to the
cathode into atomic or molecular forms. In addition,
the halogen and/or interhalogen of the electrolytic
solution is believed to undergo a reaction or reactions
with the non-aqueous solvent thereof resulting in the
formation of a compound or complex which exhibits the
observed open cirucit voltage of the cell.
The electrochemical cell according to the present
invention is illustrated further by the following
examples.
Example I
A test cell was constructed having a lithium anode,
a carbon cathode and an electrolyte comprising lithium
bromide dissolved in selenium oxychloride. In particular,
the anode of the cell was a lithium foil having a width
of about 1.~ cm., a length of about 6.6 cm. and a thickness
of about 0.056 cm. with a nickel current collector having an
extending lead or tab cold welded on the lithium foil.
The cathode was fabricated by providing a thin layer of
carbon having a width of about 1.5 cm., a length of about
7.0 cm. and a weight of about 173 milligrams and then by pressing
_9_
3049
1 the carbon layer on a thin expanded metal screen of stain-
less steel having an extending lead or tab. A separator
in the form of a sheet of Celgrad material also was
provided and placed between the anode and cathode layers,
whereupon the anode/separator/cathode assembly or combination
was rolled or wound into a cylindrical configuration and
placed in a glass vial having an outer diameter of about
1.3 cm. with the anode and cathode current collector leads
extending out through the open end of the vial. A depolarizer-
electrolyte solution was prepared comprising lithium bromidedissolved in selenium oxychloride to provide a O.lM
solution having a total volume of 2.0 ml. The solution
was injected into the glass vial, and then the open end of
the vial was sealed closed with a Teflon lined stopper in a
manner maintaining the spaced anode and cathode leads
externally accessible for electrical connection. The test
cell had an open circuit voltage of about 3.55 volts and then
an initial load voltage of about 3.45 volts when discharged
at room temperature under a constant load of 3.3 kilohms. After
fourty eight hour discharge period the load voltage was about
3.4 volts. The cell realized a total discharge capacity
of approximately 73 milliampere hours to a 3.0 volt cutoff.
Example II
A laboratory cell according to the present invention
was constructed including a lithium anode, a carbon cathode
and an ionic conductive electrolytic solution comprising
-10-
~,
113304'9
1 a halogen dissolved in a non-aqueous solvent. In
particular a Li/LiBr, SeOC12 - Br2/C cell was constructed.
The anode of the cell was a lithium foil having a
width of about 1.4 cm., a length of about 6.6 cm. and a
thickness of about 0.056 cm. with a nickel current
collector having an extending lead or tab cold welded
on the lithium foil. The cathode was fabricated by
providing a thin layer of carbon having a width of
about 1.5 cm., a length of about 7.0 cm. and an approximate
weight of from about 170 milligrams to about 190
milligrams and then by pressing the carbon layer on a
thin expanded metal screen of stainless steel having an
extending lead or tab. A separator in the form of a
sheet of Celgard material also was provided and placed
between the anode and cathode layers, whereupon the
anode/separator/cathode assembly or combination was
rolled or wound into a cylindrical configuration having
an outer diameter of about 1.0 cm. and a height of about
2.0 cm. The resulting assembly was placed in a glass
vial or other suitable container of appropriate size with
the anode and cathode current collector leads extending
out through the open end of the container. The
depolarizer-electrolyte solution was prepared in
the form of a O.lM solution of lithium bromide in a
selenium oxychloride and bromine solution, the volume
ration of selenium- oxychloride to bromine being 1:1
and the total volume of the solution being 2.0 ml.
~133V4~
1 The solution was injected or otherwise suitably introduced
into the container, and then the open end of the
container was sealed closed by a Teflon lined stopper or
other suitable closure in a manner maintaining the
spaced anode and cathode leads externally accessible
for electrical connection. The laboratory cell had an
open cirucit voltage of about 3.8 volts and then an
initial load voltage of about 3.7 volts when discharged
at room temperature under a constant load of 3.3
kilohms. After a fifty hour discharge period the
load voltage was about 3.6 volts. The cell realized
a total discharge capacity of approximately 94 milliampere
hours to a 3.0 volt cutoff.
Table I presents discharge test data obtained from
the test cell constructed according to Example I and
from the laboratory cell according to the present invention
described in Example II, both cells being discharged
at room temperature under a constant load of 3.3 kilohms
provided by a load resistor of that magnitude connected
20 across the cell terminals. ~$
-12-
113304~
1 Table I
Discharge Date For Cells Of
Examples I and II
Discharge Time Measured Load Voltage In Volts
Period In Hours Example I Example II
4.0 3.45
6.0 3.42
10.0 3.~
20.0 3.65
1024.0 3.37
30.0 3.65
48.0 3-37
3.62
55.0 3.35
~0.0 3.55
64.0 3.25
70.0 3.50
74.0 2.60
~0.0 1.~0 3.38
2090.0 2.50
95.0 2.15
100.0 2.05
102.0 2.00
Fig. 1 is a graph of load voltage as a function of
time further illustrating the data of Table I wherein
curves 10 and 12 are plots of the discharge data for the
cells of Examples I and II, respectively.
~13304~
1 It is noted that the discharge voltage of the cell of
Example II is higher than that of the cell of Example I
throughout the operating life.
Example III
A test cell was constructed having a lithium anode,
a carbon cathode and an electrolyte comprising lithium
aluminum tetrachloride dissolved in thionyl chloride.
In particular, the anode of the cell was a lithium foil
having a width of about 1.5 cm., a length of about 7.0
10 cm. and a thickness of about 0.05~ cm. with a nickel
current collector having an extending lead or tab cold
welded on the lithium foil. The cathode was fabricated
by providing a quantity of carbon having a weight of
about 0.25 gram and containing binder of Teflon material
in an amount of approximately 5% by weight and spreading
the carbon onto a nickel expanded metal element having
a width of about 1.5 cm. and a length of about 7.0 cm. and
including an extending lead or tab. A separator in the form t
of a sheet of non-woven glass material was provided and
20 placed between the anode and cathode layers. The anode/
separator/cathode assembly or combination was wound
into a cylindrical shape and inserted in a glass vial
having an outer diameter of 1.3 cm. with the anode and
cathode current collector leads extending out through
the open end of the vial. The depolarizer-electrolyte
solution was prepared comprising lithium aluminum
-14-
1133~4~
1 tetrachloride dissolved in thionyl chloride to provide a
l.OM solution having a total volume of 2.Q ml. The
solution was injected into the glass vial, and then the
open end of the vial was sealed closed with a Teflon
lined stopper in a manner maintaining the spaced anode
and cathode leads externally accessible for electrical
connection. The test cell had an open circuit voltage
of 3.60 volts and was discharged at room temperature under
a constant load of 182 ohms with the average current
10 drain rate being approximately 20 milliamperes. During
discharge the cell had an initial load voltage of about
3.4 volts and a load voltage of about 3.3 volts after a
32 hour discharge period. The cell realized a total
discharge capacity of approximately 650 milliampere
hours to a 3.0 volt cutoff.
Example IV
A laboratory cell according to the present invention
was constructed including a lithium anode, a carbon
cathode and an ionic conductive electrolytic solution
20 comprising a halogen dissolved in a non-aqueous solvent.
In particular, a Li/LiAlC14, SOC12-Br2/C cell was
constructed. The lithium anode, carbon cathode and anode/
separator/cathode combination were constructed in a manner
identical to that of Example III. Tne depolarizer-electrolyte
solution was prepared in the form of a 1.0~ solution of
lithium aluminum tetrachloride in a thionyl chloride
`~ f"
J ~`~
11330149
1 and bromine solution, there being 0.2 ml bromine and 1.8
thionyl chloride for a total volume of 2.0 ml. of the
solution. The solution was injected into the glass vial
which was then sealed in a manner similar to that of
Example III. The cellhad an open circuit voltage of 3.80
+ 0.05 volts and was discharged at room temperature (25 + 3C)
under a constant load of 182 ohms with the average
current drain rate being approximately 20 milliamperes.
During discharge the cell had an initial load voltage
of about 3.8 volts and a load voltage of about 3.3 volts
after a 32 hour discharge period. The cell realized a
total discharge capacity of approximately 700 milliampere
hours to a 3.0 volt cutoff.
Table II presents discharge test data obtained !
from the test cell constructed according to Example III
and from the laboratory cell according to the present
invention described in Example IV, both cells being
discharged at room temperature under a constant load
of 182 ohms provided by a load resistor of that
magnitude connected across the cell terminals.
-16-
1133~9
1 Table II
Discharge Data For Cells
Of Examples III and IV
Discharge Time Measured Load Voltage In Volts
Period In Hours Example III Example IV
1.0 3 37 3 75
4.0 3.35 3.70
10.0 3.32 3.60
14.0 3.30 3 ~5
1018.0 3.42
24.0 3.30 3.40
32.0 3.25 3.32
35.0 3.12
36.0 3.2
39 o 1.85
40.0 1.25 2.00
Fig. 2 is a graph of load voltage as a function of time
further illustrating the date of Table II wherein curves 14
and 16 are plots of the discharge data for the cells of
Examples III and IV, respectively. It is noted that the
discharge voltage of the cell of Example IV is higher
: than that of the cell of Example III throughout the operating
life.
Example V
A laboratory cell according to the present invention
was constructed including a lithium anode, a carbon cathode
and an ionic conductive electrolytic solution comprising a
halogen dissolved in a non-aqueous solvent. In particular,
1 a Li/LiAlC14, SGC12 - C12/C cell was constructed. The
lithium anode and carbon cathode were constructed in a
manner similar to that of Example III with the cathode
of this example having a weight of from about 180
milligrams to about 200 milligrams. The separator was of
Teflon material or, alternatively, a non-woven glass material
commercially avialable under the name Dexiglas. The anode/
separator/cathode combination was rolled into a cylindrical
shape and inserted in a glass vial in a manner identical to ',
that of Exanple III. The depolarizer-electrolyte solution was
prepared in the form of a 1.0 M solution of lithium aluminum
tetrachloride in thionyl chloride saturated with chlorine
at room temperature, the total volume of the solution being 2.0
milliliters. The solution was injected into the glass vial
which was then sealed in a manner similar to that of Example
III. The cell had an open circuit voltage of about ~,.0 volts
and was discharged at room temperature under a constant
load of 182 ohms provided by a load resistor of that
magnitude connected across the cell terminals. The discharge
test data obtained form the cell of Example V is presented
in Table III.
-18-
()49
1 Table III
Discharge Data For Cell of Example V
Discharge Time In Hours ~easured Load Voltage In Volts
1.0 3.82
3.0 3.77
4.0 3.25
17.0 3-07
19.0 2.67
Fig. 3 is a graph of load voltage as a function of time
10 wherein curve 18 further illustrates the discharge data of
Table III.
Example VI
A prototype cell according to the present invention
was constructed including a lithium anode, a carbon cathode
and an ionic conductive electrolytic solution comprising
a halogen dissolved in a non-aqueous solvent. In particular,
a Li/LiAlC14, SOC12 - Br2/C cell was constructed approximately
according to "AA" size specifications. In particular, the
dimensions of the prototype cell were 1.35 cm. outer diameter
20 by 4.70 cm. length, the casing was 304 stainless steel and
the cell was hermetically sealed using a glass-to metal seal
which was laser welded to the casing. The anode was a lithium
sheet having a width of about 4.0 cm., a length of about 5.6
cm. and a weight of about 739 milligrams with a nic~el current
collector cold welded on the lithium foil. The cathode was a
carbon sheet or layer having a width of about 4.0 cm., a length
-19 -
1 of about 6.0 cm. and a weight of about 7al milligrams which
is pressed onto a thin expanded metal screen of stainless
steel. Alternatively, the cathode could be carbon on an
expanded nickel screen. A separator in the form of a
sheet of non-woven glass material also was provided and
placed between the anode and cathode layers, whereupon the
anode/separator/cathode combination was rolled or
wound into a cylindrical configuration in a manner
similar to that of the preceding examples and placed
in the size "AA" cell casing. The depolarizer-electrolyte
solution was prepared in the form of a 1.0 ~ solution of
lithium aluminum tetrachloride in a thionyl chloride and
bromine solution, the amount by volume of bromine being 10~/o
and the total volume of the solution being approximately 4 cc.
The solution was injected or otherwise suitable introduced
into the casing. The prototype cell was hermetically
sealed by welding the glass-to-metal seal to the cell case. Prior
to sealing, electrical connections were made from the cell
case and insulated terminal to the cell electrodes or current
collectors within the casing in a suitable manner. The
prototype cell had an open voltage of about 3.~ volts
and an initial load voltage of about 3.7 volts when
discharged at room temperature under a constant load of 68.1
ohms with an average current drain of about 50 milliamperes.
After a 35 hour discharge period the load voltage was about
3.3 volts. The cell realized a total discharye capacity
of approximately 1.85 ampere hours to a 3.0 volt cutoff.
-20-
~1330~9
1 Example VII
A test cell was constructed having a lithium anode, a carbon
cathode and a electrolyte comprising lithium aluminum
tetrachloride dissolved in thionyl chloride. In particular
the anode, cathode and separator were similar to those
of Example VI, with the anode having a width of about
4.0 cm., a length of about 6.0 cm. and a weight of
about 817 milligrams. The anode/separator/cathode
combination was wound and inserted in a size "AA" casing
in a manner similar to that of Example VI. A depolarizer-
electrolyte solution was prepared comprising lithium aluminum
tetrachloride dissolved in thionyl chloride to provide a
1.0 M solution having a volume of approximately 4cc. The
solution was injected or otherwise introduced into the
casing which then was sealed closed, all in a manner
- similar to that of Example VI. The test cell had an open
circuit voltage of about 3.6 volts and an initial load
voltage of about 3.4 volts when discharged at room temperature
under a constant load of 75 ohms with an average drain
of about 45 milliamperes. After a 35 hour discharge period
the load voltage was about 3.2 volts. The cell realized
a total discharge capacity of approximately 1.69 ampere
hours to a 3.0 volt cutoff.
Table IV presents discharge test data obtained from the
prototype cell constructed according to Example VI and from
the test cell constructed according to Example VII.
-21-
1133~)49
Table IV
Dlscharge Data For Cells
Of Exsmples VI and VII
Dlscharge Timc Measured Load Voltage In Volt~
Perlod In Rours Example VI _ ExsmDle VII
1.0 3.67, 3.37
2.0 3.
20.0 3 50
24.0 3.30
30,0 3,47 3.25
35.0 3.25
36.0 3.10 3.20
Flg. 4 18 a graph of losd voltage as a function of time
further illustratlng the data of Table IV wherein curves 20 and
22 are plots of the dl~charge data for the cells of Examples
VI snd VII, respectively. It i8 noted that the dlscn~rge
voltnge of the prototype cell of Example VI is higher than that
of the test cell of Exa~ple VII throughout substantially the
entlre operating life~
Flg~. 5-8 illustrate additlonal tests conducted on
the Li/Br2 + SOC12 "M" prototype cell of Example VI. In
particular, Fig. 5 shows the discharge characterist.lc~
of the Ll/Br2 + SOC12 "M " prototype cell at room temperature
(25 + 3~C) wherein the curves 24, 26, 28, and 30 are
plot~ of the di~charge data at con~tant load3 of 332
oh~s, 182 ohms, 75 ohms and 33 ohm~, respectlvely. As in
all of tho preceding examples, the loads are provlded by
a load resistor of the indio~ed value connected across
' - -22-
11330~
the cell termln~l8. As expected, the reallzsble cspaclty
of the cell was found ~o be a functlon of the discharge
rate. A capaclty of more than 2.l ampere hours was
realized to a cutoff of 2.0 volts at an average rate
belcw 20 mllllamperes under n 182 ohm load. However,
the realized capsclty wa~ found to be much le~s st
hlgher current draln rates, L.e. 1.6 ampere ho~rs under
a 75 ohm load and about l.3 ampere hours under a 33
ohm load. Based upon the average loHd voltage and the
realized capaclty, lt follows that the prototype "M "
Li/Br2 ~ SOC12 cell ha3 a practlcal volumetrlc energy
denslty ranglng between 0.7 and l.l watt-hours per cublc
centimeter in the dlscharge rate between 10 and 100 mllliamperes.
The energy denslty at a lower dlscharge rate would
be much higher as shown ln Flg. 6. In partlcular,
Flg. 6 lllustrates the addltlonal low rate dlscharge
capaclty of the Ll/Br2 + SOC12 "M " prototype cells
whlch had been dlscharged to the 2 volt cutoff under a
di~charge rate between 10 and 20 mllllampere~. In Flg.
6, curve 32 lllustrates dlscharge data for a cell under
182 ohm~ load to a 2.0 vol~ cutoff with 2.1 ampere
houra delivered, and curve 34 illustrates dlscharge data
for a cell under a 332 ohm load to a 2.0 volt cutoff
wlth 2.1 ampere houra delivered. After cutoff both
cells were dl0charged under a 140 kllohm load. As
lllustsated ln Flg. 6, te~t cells whlch have been
dischArged to the 2.0 volt cutoff under loads of 182
ohm~ or 332 ohma contlnued to exhiblt a cell voltage of
3.4 volt~ under a 140 kilohm lo~d.
-23-
1133049
Flgs. 7 and 8 llluatrate diAcharge data from the
prototype cells of the ~ame exAmple dl~ch~rged at hlgh
and low temperature~, respectlvely. In partic~sr, Flg.
7 presents dlscharge characterlstlcs of the L~/Br2 +
SOC12 "AA" prototype cells at 60 + 3 Centlgrade. The
curves 36, 38, 40, 42 and 44 are plot~ of dlscharge
dats under load reslstances of 705 ohm~, 341 ohma, 182
ohm~, 75 ohm~, ~nd 50 ohma, respectlvely. It was found
th~t at 60 Centlgrade the realized capaclty was
somewhat lGwer than at room temperature under a slmllar
load. Flg. 8 lllustrates dlscharge charac~ristlcs of
the Ll~Br2 + SOC12 "AA" prototype cells st -40 + 3
Centlgrade. In partlculsr, the curves 48, 50, 52,
54 and 56 ln Flg. 8 are plots of dlscharge data under
load reslstances of 681 ohms, 332 ohms, 182 ohms, 75
ohmA, and 33 ohms, respectlvely. It was found that
both the low voltage and therealized capacity are
conslderably lower at -40 Centlgrsde. Furthermore,
a voltage delay was clearly noted at the beglnnlng
of the dlscharge teYt at -40C, e~pecially at hlgh
currents. Nonetheless, a practlcal volumatlc energy
density of 0.6 watt hour~ per cublc centimeter was
realized at about 10 m~lliamperes at -40C.
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~3304,9
EXAMPLE VIII
A ~i/LiAlC14, SOC12, - C12 cell of the type described
in Example V was constructed approximately to "AA"
size specifications as set forth in Example VI. The
prototype cell had an open circuit voltage of about 3.9
volts, and the cell realized a total discharge capacity
of approximately 2.0 ampere hours when discharged under
a 20 ohm load at room temperature to a 2.0 volt cutoff.
EXAMPLE IX
-- ----
A Li/LiAlC14, SOC12 - BrCl cell was constructed
to approximately "AA" size specifications as described
in Example VI. The prototype cell had an open circuit
voltage of about 3.9 volts, and the cell realized a
total discharge capaicty of approximately 2.1 ampere
hours when discharged under a 182 ohm load at room
temperature to a 2.0 volt cutoff. In Fig. 9 the curve
58 is a plot of a cell voltage against capacity illustrating
the discharge characteristics of the cell under a 182
ohm load.
It is therefore apparent that the present invention
accomplishes its intended objects. While several
embodiments of the present invention have been described
in detail, this is for the purpose of illustration, not
limitation.
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