Note: Descriptions are shown in the official language in which they were submitted.
CA 02755597 2011-10-20
HIGH TEMPERATURE LITHIUM BATTERY, HAVING INITIAL LOW
TEMPERATURE USE CAPABILITY
FIELD OF THE INVENTION
[0001] The present invention relates to batteries.
[0002] BACKGROUND OF THE INVENTION
[0003] High energy density batteries are typically needed and used in
oil drilling
operations, namely to power various downhole electrical equipment, and are
frequently of the
lithium metal anode type, which provide the needed high energy density in
comparison to
conventional primary batteries (ie non-rechargeable type batteries).
[0004] Typically, in oil drilling operations such batteries are
located downhole,
proximate a drill bit, to provide electrical power to downhole equipment,
including sensors and
measurement-while-drilling ("MWD") mud pulsers, which send mud pulses encoded
with
information from such sensors uphole to surface so as to assist drilling
operators in steering the
drilling equipment into oil bearing formations, and further giving data as to
the types and
densities of rock formations encountered during the drilling of such oil
wells.
[0005] As well depth increases, temperatures may increase from an
ambient surface
temperature (of say, 23 C) to temperatures exceeding 100 C, and frequently
temperatures in the
range of 125 C to 200 C are typically encountered at several thousand metres
of well depth.
[0006] Lithium batteries typically employ lithium metal or a lithium
alloy as the anode.
Substantially pure lithium may be used as the anode, and in certain types of
lithium batteries
liquid thionyl chloride [SOC12 ] may be used as the cathode, to produce a flow
of electrons. The
electrochemical oxidation-reduction reaction which occurs to produce such flow
of electrons may
be as follows:
at the anode: Li,u+ + e-
at the cathode: 4Li+ + 4e- + 2S0C12 ¨> 4LiC1 + SO2 + S
overall reaction: 4Li + 2S0C12 ¨> 4LiC1 + SO2 + S
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[0007] Unfortunately, pure lithium metal has a melting temperature of
180.5 C, and
standard lithium batteries are accordingly limited to temperatures of about
160 C to thereby
avoid melting of the lithium anode within the battery and consequent explosion
of the battery, or
at a minimum failure of the operation of the battery. Accordingly, lithium
batteries which employ
substantially 100% lithium as the anode will typically fail at high
temperatures of the magnitude
encountered when drilling several thousand metres beneath the surface, where
temperatures are
often, as mentioned above, in the 200 C range.
[0008] It is known to alloy lithium metal in a lithium battery with 10%
magnesium in
order to raise the melting point of the resulting 90%Li-10%Mg alloy, thereby
raising the
maximum temperature to which such a lithium battery may be exposed to up to
200 C, thus
rendering lithium-mg alloy batteries usable in downhole applications where
temperatures may
regularly approach such temperature. (Battery manufactures typically stipulate
such batteries are
temperature- limited to 180 C, to thereby provide a small "safety buffer")
[0009] It is further known to alloy lithium metal in a lithium battery
with 25%
magnesium in order to raise the melting point of the resulting Li-Mg alloy
anode up to 220 C,
thereby raising the maximum temperature to which such a lithium battery may be
exposed, thus
rendering lithium-mg alloy batteries usable in downhole applications where
temperatures may
regularly approach such temperature. (Battery manufactures typically presently
stipulate such
batteries are temperature limited to 200 C to thereby similarly stipulate a
small "safety buffer"
of approximately 20 C)..
[0010] Notably, however, while alloying the lithium in the lithium anode
with magnesium
of up to 25% allows operation of such battery up to the relative high
temperature of 200 C,
unfortunately such step has the negative side effect of significantly reducing
the power and
voltage available from such battery at lower temperatures, namely temperatures
less than about
50-100 , particularly where a battery may have been sitting idle at such room
temperature for
periods of approximately forty (40) days or more. This negative side effect
produces a significant
obstacle to downhole tool companies desiring to test electronic equipment
(which is to be powered
by such batteries at surface under ambient temperatures, typically at
temperatures less than 50 C
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and typically at ambient room temperature of approximately 23 C) to ensure
such equipment is
properly operating at surface before inserting such equipment downhole for use
in drilling
operations. This is due to the fact that the power and voltage available from
such a lithium metal
alloy anode battery at ambient temperatures, for example 23 C, is relatively
low, and not
sufficient to allow adequate and proper testing of the electrical equipment in
the tools powered
by such battery at well surface due to insufficient power/voltage supplied by
such battery at such
ambient temperatures.
[0011] To overcome the above negative side effect, downhole tool
companies presently
apply a heater blanket to tools containing a lithium battery (or battery pack)
at surface , in order
to significantly raise the temperature of the battery(ies) within the tool at
surface to a range of
about 50-70 C, in order to thereby obtain sufficient power and voltage from
such lithium
battery(ies) at such higher temperatures to allow equipment to be tested at
surface to ensure
proper operation before being inserted downhole.
[0012] Unfortunately, malfunction of the heater and/or overheating
of the lithium
battery(ies) will result (and has resulted) in explosion of such lithium
battery(ies) on a number
of occasions. This is a serious and substantial safety concern at a drill
site, where risk to worker
safety and risk of damage or loss of expensive sensor equipment, are serious
and over-riding
concerns. Unfortunately, overheating of such lithium-mg alloy batteries has
resulted in at least one
worker fatality due to the resulting explosion of the lithium battery during
heating.
[0013] Accordingly, a real and substantial need exists in the
downhole tool industry for a
battery which can provide sufficient power and voltages [typically 3.6 to 3.9
volts (open circuit)
from a single cell] to various electrical equipment at relatively low ambient
temperatures such as
in the range of 23 C for a brief initial period to allow testing of such
equipment at surface, but
which battery may be subsequently exposed to higher temperatures in the range
of up to 200 C
and will continue to reliably operate when such battery and associated
downhole tool is located
downhole.
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SUMMARY OF THE INVENTION
[0014] Accordingly, in order to overcome the necessity to heat a battery
of the prior art
(and thereby running the risk of explosion due to improper heating) when
testing electronic
equipment powered by such battery at surface, in one broad aspect the present
invention relates to
a modification of the anode of a high-temperature battery, typically a lithium
battery, to thereby
allow such battery to provide, for a limited initial time period, the
requisite power and voltage
output at temperatures lower than what the high-temperature battery is
designed to operate, yet
such battery thereafter be capable of being exposed to high temperatures
downhole without
exploding or failing, yet maintaining sufficient voltage and power output.
[0015] Accordingly, in a first broad aspect of the present invention,
the present invention
comprises a battery for operating initially at lower temperatures for a finite
period, which battery
is further adapted to later operate at higher temperatures , comprising:
(i) an anode comprising a first metal which is a strong reducing agent, and at
least
one further substance adapted to increase a melting point of said first metal,
and
(ii) said anode having applied to a surface thereof a thin, substantially
uniform
layer of said first metal in substantially pure form.
[0016] Advantageously, through the electrochemical reaction during
discharge of the
battery at surface at ambient temperatures, the thin layer of the first metal
is typically exhausted
in the resulting electrochemical reaction and none is thereby left to melt to
cause potential
explosion. Moreover and in any event, the amount of first metal in the thin
layer of the battery of
the present invention, which typically in a preferred embodiment is of a
nominal thickness of
approximately 0.002 inches (.0508mm), is of a sufficiently small amount that
even if it did melt
such quantity would not substantially raise the risk of explosion.
[0017] In a preferred embodiment, the first metal is lithium, and the
anode is a lithium
alloy anode, and in a further embodiment the anode comprises a lithium-
magnesium alloy
comprised of at least 10% magnesium, and preferably greater than 10% but no
more than 25%
(wt) magnesium with a remainder substantially comprised of lithium, which base
anode with a
magnesium content of 25% and a thin coating of approximately 0.002 inches of
pure lithium
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allows for operating initially at temperatures less than 160 C and later
operating at higher
temperatures of up to 200 C. The cathode is in a preferred embodiment thionyl
chloride, but may
be any other suitable cathodic material, including sulfuryl chloride, which
will provide sufficient
emf voltage 'V' in the redox reaction to power the desired electrical
equipment, provided such
cathode and anode are of sufficient surface area to provide sufficient current
i (and thus
electrical power, where power P=ixV) to power the electrical equipment.
[0018] In a further preferred embodiment, the thin layer of
substantially pure lithium is of
a thickness in the range of 0.0019 to 0.0025 inches ( .04826-.0635mm), which
thickness can
thereby provide an initial short time period , of at least 10 minutes and
typically at least 15
minutes under discharge rates typical of the equipment designed to be operated
by which
relatively high voltages and power can be drawn from the lithium battery, yet
the risk when such
battery is subsequently exposed to higher temperatures is minimal even if
significant quantities of
pure lithium in such thin layer remained on the surface of the anode.
[0019] In another embodiment of the present invention, the invention
relates to a method
of making a high temperature battery for initially operating at temperatures
in the range less than
the melting point of a first metal which acts as a strong reducing agent
within said battery, which
battery is further adapted to later operate at subsequent higher temperatures
exceeding the
melting point of said first metal, comprising the steps of:
preparing a metallic alloy anode, substantially comprised of a first metal
which
acts as a strong reducing agent and containing a further substance to raise
the melting point of said
alloy anode above the melting point of said first metal in substantially pure
form; and
applying, to an exterior surface of said anode, a thin substantially uniform
layer of
said first metal, in substantially pure form.
[0020] In a further refinement, said step of preparing a metallic alloy
anode comprises the
step of forming a substantially flat member having mutually opposite flat
sides; and said step of
applying, to an exterior portion of said anode, a thin substantially uniform
layer of said first
metal in substantially pure form comprises the step of applying, under
pressure, a thin sheet of
said first metal in substantially pure form to at least a portion of one of
said mutually opposite flat
sides.
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[0021] In one refinement of the above method, the step of applying
said layer of first
metal in substantially pure form, under pressure, comprises the step of
placing a strip of said
metallic alloy anode over a thin sheet of substantially pure first metal, and
inserting the strip and
sheet through a pair of pressure rollers.
[0022] In a preferred method of the above invention, the first metal
is lithium, and in yet a
further refinement, said step of formulating said metallic alloy anode
comprises the step of
forming a lithium magnesium alloy comprising approximately 25% magnesium and
75% lithium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In the accompanying drawings, which illustrate one or more
exemplary
embodiments and are not to be construed as limiting the invention to these
depicted
embodiments:
FIG. la is a schematic top sectional view through a bobbin- type battery made
in
accordance with the present invention, taken along plane A-A of FIG. lb;
FIG. lb is a schematic side sectional view of the bobbin-type battery of the
present
invention shown in FIG. lb;
FIG. 2a is a schematic sectional view through a dual-anode type battery made
in
accordance with the present invention, taken along plane B-B of FIG. 2b;
FIG. 2b is a schematic side sectional view of the dual-anode type battery
shown in FIG.
2a of the present invention;
FIG. 3a is a schematic view of a spiral-wind ("jelly roll") type battery made
in
accordance with the present invention;
FIG. 3b is a perspective partially-exploded sectional view of the spiral wind
("jelly roll")
type battery shown in FIG. 3a of the present invention, taken along plane C-C
of FIG. 3a;
FIG. 4 is a graph of voltage versus time with respect to a control lithium
battery and a test
lithium battery, each of "DD size", wherein said test lithium battery is made
in accordance with the
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present method, immediately after manufacture of both the control and test
batteries, with an initial
250mA start-up current being drawn from the batteries, at 20 C;
FIG. 5 is a graph of voltage versus time with respect to a control lithium
battery and a test
lithium battery, each of "DD size", wherein said test lithium battery is made
in accordance with the
present method, said graph obtained after 3 days storage of said batteries at
20 C;
FIG. 6 is a graph of voltage versus time with respect to a control lithium
battery and a
test lithium battery, each of "DD size" wherein said test lithium battery is
made in accordance with
the present method, said graph obtained after 15 days storage of said
batteries at 20 C;
FIG. 7 is a graph of voltage versus time with respect to a control lithium
battery and a
test lithium battery, each of "DD size", wherein said test lithium battery is
made in accordance
with the present method, said graph obtained after 40 days storage of said
batteries at 20 C;
FIG. 8 is a graph of voltage versus time with respect to a control lithium
battery and a test
lithium battery, each of "DD size", wherein said test lithium battery is made
in accordance with the
present method, said graph obtained after 90 days storage of said batteries at
20 C;
FIG. 9 is a graph of voltage versus time with respect to a control lithium
battery and a test
lithium battery, each of "DD size", wherein said test lithium battery is made
in accordance with the
present method, said graph obtained after 3 days storage of said batteries at
50 C;
FIG. 10 is a graph of voltage versus time with respect to a control lithium
battery and a
test lithium battery, each of "DD size", wherein said test lithium battery is
made in accordance
with the present method, said graph obtained after 6 days storage of said
batteries at 50 C;
FIG. 11 is a graph of voltage versus time with respect to a control lithium
battery and a test
lithium battery, each of "DD size", wherein said test lithium battery is made
in accordance with the
present method, said graph obtained after 10 days storage of said batteries at
50 C;
FIG. 12 is a graph of voltage versus time with respect to a control lithium
battery and a
test lithium battery, each of "DD size", wherein said test lithium battery is
made in accordance
with the present method, said graph obtained after 14 days storage of said
batteries at 50 C;
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FIG. 13 is a graph of voltage versus time with respect to a control lithium
battery and a
test lithium battery, each of "DD size", wherein said test lithium battery is
made in accordance
with the present method, said graph obtained after 24 days storage of said
batteries at 50 C;
FIG. 14 is a graph of voltage versus time with respect to a control lithium
battery and a
test lithium battery, each of "DD size", wherein said test lithium battery is
made in accordance
with the present method, said graph obtained after 40 days storage of said
batteries at 50 C; and
FIG. 15 is a graph of voltage versus time, at room temperature of 24 C, with
respect to a
dual-anode size DD lithium battery of the present invention, showing the
relatively high voltage of
approximately 3.5 volts which is thus obtainable for a 4.2 hour period, with a
.002 nominal
thickness 100% pure lithium layer overlying a lithium-magnesium alloy anode.
DETAILED DESCRIPTION OF SOME PREFERRED EMBODIMENTS
[0024] In regard to the drawings, like components of the battery of the
present invention
are identified with identical reference numerals.
[0025] The battery of the present invention may take the form of (but is not
limited to) a
modified bobbin-type battery 10 as shown in FIG.'s la &lb ; a modified dual-
anode type battery
12 as shown in FIG.'s 2a & 2b, or a modified spiral wound ("jelly roll") type
battery 14 as shown
in FIGs. 3a & 3b.
In all embodiments of the battery 10, 12, and 14 of the present invention
shown in FIG.'s
la, lb, FIGs. 2a, 2b, and FIGs. 3a, 3b respectively, such battery comprises a
metallic alloy
anode 20 formed of a first metal that is a strong reducing agent, and at least
one further compound
adapted to increase a melting point of said first metal in said anode 20. In
one embodiment, the
first metal in said metallic alloy anode 20 is lithium, which is the lightest
known metal and a
strong reducing agent, and the alloying compound is magnesium. The lithium-
magnesium alloy
may be formed by direct-alloying by the melting of mole percent specific
mixtures of Li and Mg
metal under vacuum, or alternatively via kinetically-controlled vapour
formation and deposition
(KCVD) of a Li¨Mg alloy on a substrate.
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[0026] The metallic alloy anode 20 has applied to at least one surface thereof
a thin,
substantially uniform layer 22 of said first metal in substantially pure form.
Such pure form may
be 99.8% pure lithium, lithium being a metal that is a strong reducing agent ,
and may be sourced
from such suppliers as FMC Corporation or Chemetall Foote Corp., each of North
Carolina,
U.S.A. The application/bonding of the thin layer 22 to the metallic alloy
anode 20 may be
accomplished, where the first metal is lithium, by pressure rolling a thin
sheet of such first metal
onto the thicker metallic alloy anode 20 containing such first metal in alloy
form. One such
pressure roller device particularly suitable for bonding a thin layer 22 of
lithium to a lithium
magnesium alloy anode 20 is a Model No. ECR001 Pressure Roller manufactured by
Noremac
Industrial Automation Ltd.
[0027] Application of a thin layer 22 of the first metal to metallic anode 20
by pressure
rolling is particularly suited where the metallic anode 20 is initially formed
in a substantially flat
strip, in the range of 0.050-0.060 inches (ie 1.27-1.52mm) thick, although due
to the ductility of
such anode 20 when comprised of at least 75% (wt) of lithium, such anode 20
may later be easily
deformed into , for example, cylindrical form (ref. FIG. la, lb, 2a, 2b, ) or
into a spiral form
(FIG. 3a, 3b) for insertion in a cylindrical canister 25 which serves as the
lithium battery
protective exterior. However, thin layer 22 may alternatively be overlayed
with or bonded to
metallic alloy anode 20 by other known methods, including plasma coating
(deposition) methods
or other similar methods of application, which may be more suited if the first
metal is of a less
ductile nature, and pressure rolling subsequent deformation into cylindrical
format is not an
option.
[0028] If desired, and as described with respect to the "jelly roll" battery
14 as shown in
FIG. 3a, 3b, a pair of thin sheets of such first metal may be bonded to each
side metallic anode 20
to form a thin layer 22a, 22b on each respective side of metallic alloy anode
20, but in the
embodiment of FIG's. la, lb, and FIG.'s. 2a, 2b, only one side of such
metallic alloy anode 20
has a thin layer 22 bonded thereto
[0029] Notably, for the purposes of the present invention, in order to give a
period of at
least 15 minutes of sufficient draw-down current, voltage, and power from the
battery 10, 12, or
14 at ambient temperatures (ie less than approximately 50 C) to thereby allow
drilling technicians
and well operators to initially test and operate electrical equipment at
surface prior to insertion of
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such equipment and battery downhole, it is contemplated in one embodiment of
the invention
that the thickness of the thin layer 22 be relatively small in comparison to
the thickness of the
metallic alloy anode 20, and in a preferred embodiment, since the vast
majority of the current
being drawn from the battery will be when operating such electrical equipment
downhole, that the
thickness of the thin layer 22 be in the range of approximately 0.0019 to
0.0025 inches ( .04826-
.0635mm). As seen from FIG. 15, and as more fully explained herein, such
thickness of layer 22,
with the battery 12 dimensions of a DD size battery such will provide a short
interval of up to
4.2 hours at a drawdown current of 250mA. By keeping the thickness of the thin
layer 22
relatively small, such ensures that even if the battery 10, 12, 14 was to be
inserted downhole
immediately without such initial testing and thereby without initial discharge
at surface where the
thin layer 22 would otherwise become consumed in the electrochemical reaction,
the amount of
first metal in such thin layer 22 (which would immediately become melted due
to the higher
downhole temperatures) is not of sufficient quantity to cause any significant
electrical "short" in
such battery 10, 12, 14 when melted, and thus avoids any potential explosion
of such battery 10,
12, 14 and consequent loss of electrical power to the downhole electrical
equipment..
[0030] FIGs. la and lb show a bobbin-type lithium battery 10 of the present
invention,
comprising a cylindrical canister 25, typically of an electrically conductive
metal. A metallic alloy
anode 20 formed of 90% lithium and 10% magnesium, or alternatively up to 25%
magnesium and
75% lithium has bonded thereto by pressure rolling (in the method described
above) a thin [0.002
inch (.0508mm) nominal thickness] layer 22 of 99.8% pure lithium. The
resulting anode 20 is
wound into a cylindrical shape and inserted in canister 25, which may serve as
the negative
terminal of battery 10. A non-electrically conductive separator 30 comprising
a thin sheet of
nonwoven fibreglass physically and electrically isolates the anode 20 and
negative terminal 50 of
battery 10 from a carbon element 32 which serves as the cell cathode and is
connected to the cell
positive terminal 42. A catholyte 40, preferably thionyl chloride [SOC12] or
alternatively
sulfuryl chloride [S02C12] , is inserted in battery 10. Catholyte 40, when in
the form of thionyl
chloride, has dissolved therein an electrolyte salt in the form of lithium
tetrachloroaluminate
[LiA1C14] and/or lithium tetrachlorogallate [LiGaC14] to increase ion
conductivity of the thionyl
chloride catholyte and increase current rates, wherein the thionyl chloride
catholyte acts as the
cathode for the battery 10. An end cap 45 is welded to canister 25, and a
glass-metal seal
member 44 is used to retain the catholyte 40 within battery canister 25.
Battery 10 via its positive
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terminal 42 and negative terminal 50 is used to provide electrical current to
an electrical device,
symbolized by resistance "R" in FIG. lb.
[0031] In preferred embodiments of the battery 10, 12, 14 of the present
invention, for the
relatively strict sizes of batteries utilized in downhole equipment, ranging
from AA to DD fie for
cylindrical battery sizes from AA (14.55mm x 50.3 mm ie .57 in x 1.98in.) to
DD (47.2 mm dia. x
127 mm length ie 1.86 in x 5.0 in.)], namely where metallic alloy anode 20 is
initially formed
from a substantially flat Li-Mg alloy consisting of 75% Li and 25% Mg for
which the thin layer
22 of pure lithium is applied thereto, for a bobbin- type battery 10 the
metallic alloy anode 20
may be of dimensions 2.0in in length x 0.050in in thickness (ie 50.8mm x
1.27mm).
[0032] FIG.'s 2a & 2b show a battery 12 of the present invention of the "dual
anode"
type, having a pair of anodes 20a, 20b, which together result in increased
surface area to thereby
allow such dual-anode battery 12 to provide higher current than the bobbin-
type battery 10. In
such configuration a first (outer) metallic alloy anode 20a, rolled from a
substantially flat
substrate into a cylindrical shape, is provided. In one embodiment metallic
alloy anode 20a
comprises a flat strip of Li-Mg alloy onto which is pressed a thin (.002 inch
nominal thickness)
sheet 22a of 99.8% pure Li, and the so-formed anode 20a wound into a cylinder
and inserted in
cylindrical battery canister 25, with sheet 22 forming the inner periphery of
cylindrical anode 20a.
A second (inner) anode 20b is similarly formed, likewise comprised of a Li-Mg
metallic alloy and
similarly having a thin sheet 22b of substantially pure Li applied to an outer
surface thereof, and
wound in a cylinder and inserted in battery canister 25 in spaced-apart
position from outer anode
20a, as shown in FIG. 2b. The thickness of the thin layer 22b on anode 20b may
be different
than the thickness of thin layer 22a on anode 20a, or may be approximately the
same .
Intermediate thin layer 22a and 22b is a carbon element 32, which has on
either side thereof
respective fibreglass insulating layers 30a, 30b.
[0033] As seen from FIG.'s 2a & b, the alternative-configuration dual-anode
battery 12
of the present invention comprises a pair of cylindrical lithium-magnesium
alloy anodes 20a,
20b, with (outer)anode 20a being larger in diameter than (inner) anode 20b,
with anode 20a
concentrically surrounding anode 20b. Outer anode 20a has applied to
an inner circular
periphery thereof, by any one of the methods above described and preferably by
pressure rolling,
a thin layer 22a of substantially pure lithium. Similarly, inner anode 20b has
applied to an outer
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,
circular periphery thereof, via any one of the methods described above, a thin
layer 22b of
substantially pure lithium. Thin layer 22a may or may not be the same
thickness as thin layer
22b, although preferably, for equal electrochemical discharge times when
current is drawn from
such battery 12, the thickness of layer 22a and 22b is the same. Disposed in a
cylindrical space
80 formed intermediate thin layer 22a on outer cylindrical anode 22a and thin
layer 22b on inner
anode 22b is cylindrical carbon element 32 which serves as the battery
positive terminal 42. A
pair of non-electrically conductive separators 30a, 30b each comprising a thin
sheet of
nonwoven fibreglass, physically and electrically isolate the anodes 20a, 20b
from each other.
Electrically conductive leads 70 connected to anode 20a to 20b may be used to
provide negative
anode 70 for battery 12. Carbon element 32 is electrically coupled to battery
positive terminal 42
as shown in FIG.'s 2a,b. An end cap 45 is welded to canister 25, and a glass-
metal seal member
44 is used to retain the catholyte 40 within battery canister 25. Catholyte 40
in the form of thionyl
chloride having dissolved therein an electrolyte salt in the form of lithium
tetrachloroaluminate
[LiA1C14] and/or lithium tetrachlorogallate [LiGaC14] is injected into battery
12, to act as the
cathode for the battery 12. Battery 12 via its positive terminal 42 and
negative terminal is used to
provide electrical current to an electrical device, symbolized by resistance
"R" in FIG. 2b.
[0034] A "DD" sized battery 12 (approximately 5.0 inches in length, and 1.86
inches in
diameter) of the dual- anode configuration, having an outer anode 20a (90%Li,
10%Mg) of
approximately 2.0 inches in width and .050 in thickness, to which a thin layer
22a of .002 inches
of pure lithium is applied, and having a inner anode 20b (90%Li, 10% Mg) of
approximately
1.85 inches in width and .060 inches in thickness to which a thin layer 22b of
.002 inches of pure
lithium is applied, with an initial 90 day storage period, can provide, with a
drawdown current
of 250ma and at a temperature of at 20 C, a voltage between 2.5 to 2.8 volts
for a period of at
least 900 seconds (ie 15 minutes) (see FIG. 8) .
[0035] Alternatively, with no initial storage period, a similar battery at a
temperature of
24 C and with a similar drawdown current of 250mA, can provide for a period of
4.2 hours a
voltage approaching the battery maximum, namely 3.5 volts (see Fig. 15).
[0036] FIG.s 3a-3b show a battery 14 of the present invention of the "spiral"
or "jelly-
roll" configuration, which as a result of the increased surface area of the
anode 20a arising from
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spiral winding of the anode 20a within canister 25, can provide higher current
than either the
bobbin-type battery 10 or "dual anode" battery 12.
[0037] For the spiral battery 14 of FIG. 2a, 2b, a substantially flat strip of
Li-Mg metallic
alloy anode 20a is provided, onto a portion of the (outer) side surface of
anode 20a is pressed a
thin (.002 inch nominal thickness) sheet 22a of 99.8% pure Li over a portion
(ie an inner side
surface and an outer side surface) of anode 20a. Pressed onto an opposite
(inner) side is a similar
thin layer 22b of substantially pure Li metal. An electrically insulating thin
sheet 30a which in
one embodiment is a fibreglass weave material is further applied to such inner
side, and over
which is applied a carbon sheet 32 substantially comprised of carbon black,
which forms the
positive electrode for battery 14. Over carbon sheet 32 is applied a similar
electrically insulating
thin sheet 30b to thus, in combination with insulating sheet 30a, electrically
insulate carbon sheet
32 on which positive charges are formed, from each of anodes 20a, 20b on which
negative
electrical charge is formed. The resulting sheet [of mutually-overlying
'sandwiched' layers 20a,
22a, 30a, 32, and 30b] is wound in a spiral configuration, with portions of
such resulting sheet
overlapping as shown in FIG. 3a, and inserted within battery casing 25.
[0038] A cathode 40, and more particularly a catholyte in the form of thionyl
chloride
having dissolved therein an electrolyte salt in the form of lithium aluminum
chloride [LiA1C14]
and/or lithium gallium chloride [LiGaC14] is injected into battery 14, to act
as the cathode for the
battery 14 . Alternatively sulfuryl chloride may be used as the catholyte. A
liquid-retaining seal
56 is provided immediately above upwardly facing ends of layers 22a, 20a, 22b,
30a, 32, and
30b as shown in FIG. 3b, and an electrically insulating material 56 applied to
a top surface of
seal 56. A metallic end cap 60 is welded to a top end of canister 25, and a
glass-metal seal
member 44 is used to retain the catholyte 40 within battery canister 25.
Positive electrode 42,
electrically coupled to carbon element 32, and negative electrode 70
electrically coupled to anodes
20a, 20b, protrude from a top end of battery 14..
[0039] As evidence of the utility and practicality of the high temperature
battery of the
present invention in attaining at least one of its objects, namely providing a
high temperature
battery adapted to operate in relatively high temperatures yet allowing
substantial current and
voltages for an initial limited time period at lower temperatures, as series
of tests were carried out.
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CA 02755597 2011-10-20
Example t
[0040] A "dual ¨anode" DD sized battery 12 of the present invention was
constructed in
the manner described above, having a metallic alloy anode consisting of 90% Li
and 10% Mg.
[0041] In each case anodes 20a, 20b having a thin layer 22a, 22b of
substantially pure
(99.8%) Li of nominal 0.002 inch thickness. The dimensions of anode 20a were
2.0 inches x
0.050 inches, and of anode 20b were 1.85inches x 0.060 inches.
[0042] Using an intial start-up load current of 250mA, voltage output of a
plurality of
dual-anode type battery 12 were measured over a 15 minute initial period (900
seconds) , at 20 C
with various pre-storage times for each of the respective batteries tested,
namely 0 days, 3 days,
15 days, 40 days, and 90 days. Voltage output continued to be monitored after
removal of the
250mA load, for a further 300 seconds, for a total voltage monitoring time of
1200 seconds.
[0043] Graphs of measured voltage output versus time, for each of the five DD
batteries
tested, for each of the pre-storage times of 0, 3, 15, 40, and 90 days, are
set out respectively in
FIG.s 4-8, as compared to voltage output over a similar time period from a
"control" battery not
having any thin layer of pure Li.
[0044] As may be seen from FIGs. 4-7, voltage output of the "test" battery in
accordance
with the above invention in all instances exceeded the voltage output of the
"control" battery,
regardless of the initial storage period.
[0045] With respect to test having pre-storage of 90 days (ref. FIG. 8), save
for the initial
start-up period of approximately 100 seconds (during which time effects of
battery passivation
may have been playing a role), thereafter and up to 15 minutes thereafter the
voltage output of the
"test" cell significantly exceeded that of the control high temperature
battery, for the duration of
the test (15 minutes) where load was applied.
Example 2
[0046] A similar comparison test was carried out as in Example 1 above, again
at 20 C
save that the pre-storage for each of the respective batteries tested, namely
3 days, 6 days, 10
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CA 02755597 2011-10-20
days, 14 days, 24 days, and 40 days, occurred at temperatures of 50 C, instead
of at 20 C as in
Example 1.
[0047] Graphs of measured voltage output versus time, for each of the five DD
batteries
tested, for each of the pre-storage times of 3, 6, 10, 14, 24, and 40 days
respectively, are set out
respectively in FIG.s 9-14, as compared to voltage output versus time from a
"control" battery
not having any thin layer of pure Li.
[0048] As may be seen from FIGs. 9-14, voltage output of the "test" battery in
accordance
with the above invention in all instances exceeded the voltage output of the
"control" battery,
regardless of the initial storage period, for an initial period of at least 15
minutes whereafter the
250mA load was removed..
Example 3
[0049] To determine the approximate time period for which a Li-Mg anode having
a
substantially pure coating applied thereto in accordance with the method of
the present invention
could operate at room temperature before the electrochemical reaction (during
discharge of the
battery) used up such thin layer of pure lithium, a lithium-magnesium battery
of the type prepared
in Examples 1 and 2 was prepared.
[0050] More specifically, a DD size battery, having a lithium-magnesium alloy
anode
comprising 90% Li and 10% Mg, and having a nominal .002 inch strip /layer of
substantially
99.8% pure Li) lithium applied thereto, was prepared. Such prepared battery
had a pre-storage
period at 24 C of less than 3 days.
[0051] At room temperature (24 C), and with a current load of approximately
250mA
being drawn from such cell, voltage from such battery was measured over a time
period of
approximately 13 hours.
[0052] Fig. 15 shows a graph of the voltage measured from such cell, as a
function of
time.
[0053] As may be seen from Fig. 15, by the application of a substantially pure
, thin, layer
of lithium metal to a substrate comprising a 90%-10% lithium-magnesium alloy
anode, a
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CA 02755597 2011-10-20
,
maximum battery voltage of approximately 3.45 volts was capable of being
obtained and
maintained for a short interval of time, namely for a period of approximately
4.2 hours, at a room
temperature range (namely 24 C).
The scope of the claims should not be limited by the preferred embodiments set
forth in
the foregoing examples, but should be given the broadest interpretation
consistent with the
description as a whole, and the claims are not to be limited to the preferred
or exemplified
embodiments of the invention.
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