U.S. patent application number 11/870544 was filed with the patent office on 2009-02-05 for stabilized lithium metal powder for li-ion application, composition and process.
This patent application is currently assigned to FMC Corporation, Lithium Division. Invention is credited to Brian Anthony Christopher Carlin, B. Troy Dover, Kenneth Brian Fitch, Yuan Gao, Jian-xin Li, Yangxing Li, Prakash Thyaga Palepu, Marina Yakovleva.
Application Number | 20090035663 11/870544 |
Document ID | / |
Family ID | 39091992 |
Filed Date | 2009-02-05 |
United States Patent
Application |
20090035663 |
Kind Code |
A1 |
Yakovleva; Marina ; et
al. |
February 5, 2009 |
STABILIZED LITHIUM METAL POWDER FOR LI-ION APPLICATION, COMPOSITION
AND PROCESS
Abstract
The present invention provides a lithium metal powder protected
by a wax. The resulting lithium metal powder has improved stability
and improved storage life.
Inventors: |
Yakovleva; Marina;
(Gastonia, NC) ; Gao; Yuan; (Monroe, NJ) ;
Fitch; Kenneth Brian; (Cherryville, NC) ; Dover; B.
Troy; (Kings Mountain, NC) ; Palepu; Prakash
Thyaga; (Gastonia, NC) ; Li; Jian-xin; (North
Brunswick, NJ) ; Christopher Carlin; Brian Anthony;
(Lawrenceville, NJ) ; Li; Yangxing; (Belmont,
NC) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Assignee: |
FMC Corporation, Lithium
Division
|
Family ID: |
39091992 |
Appl. No.: |
11/870544 |
Filed: |
October 11, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60829378 |
Oct 13, 2006 |
|
|
|
Current U.S.
Class: |
429/231.95 ;
252/182.1; 427/115 |
Current CPC
Class: |
Y02E 60/10 20130101;
H01M 4/40 20130101; H01M 4/1315 20130101; H01M 4/587 20130101; H01M
4/133 20130101; B22F 2999/00 20130101; B22F 1/02 20130101; H01M
4/134 20130101; H01M 10/052 20130101; H01M 4/131 20130101; H01M
4/485 20130101; B22F 1/0062 20130101; H01M 4/387 20130101; H01M
4/366 20130101; B22F 2998/10 20130101; H01M 4/628 20130101; H01M
4/386 20130101; B22F 1/0077 20130101; H01M 2004/027 20130101; B22F
2998/10 20130101; B22F 1/0062 20130101; B22F 1/02 20130101; B22F
2999/00 20130101; B22F 1/0062 20130101; B22F 1/0077 20130101 |
Class at
Publication: |
429/231.95 ;
252/182.1; 427/115 |
International
Class: |
H01M 4/58 20060101
H01M004/58 |
Claims
1. A stabilized lithium metal powder coated with a wax.
2. The stabilized lithium metal powder of claim 1, wherein the wax
has a thickness of 20 .mu.m to 200 .mu.m.
3. The stabilized lithium metal powder of claim 2, wherein the wax
is selected from the group consisting of natural waxes, synthetic
waxes, petroleum waxes, and microcrystalline waxes.
4. The stabilized lithium metal powder of claim 3, further
comprising an inorganic coating.
5. The stabilized lithium metal powder of claim 4, wherein the
inorganic coating is selected from the group consisting of
Li.sub.2CO.sub.3, LiF, Li.sub.3PO.sub.4, SiO.sub.2,
Li.sub.4SiO.sub.4, LiAlO.sub.2, Li.sub.2TiO.sub.3, and
LiNbO.sub.3.
6. An anode comprising a host material capable of absorbing or
desorbing lithium in an electrochemical system wherein the
stabilized lithium metal of claim 1 is dispersed in the host
material.
7. An anode comprising a host material capable of absorbing or
desorbing lithium in an electrochemical system wherein the
stabilized lithium metal of claim 3 is dispersed in the host
material.
8. The anode of claim 6, wherein said host material comprises at
least one material selected from the group consisting of
carbonaceous materials, silicon, tin, tin oxides, composite tin
alloys, transition metal oxides, lithium metal nitrides, graphite,
carbon black, and lithium metal oxides.
9. The anode of claim 7, wherein said host material comprises at
least one material selected from the group consisting of
carbonaceous materials, silicon, tin, tin oxides, composite tin
alloys, transition metal oxides, lithium metal nitrides, graphite,
carbon black, and lithium metal oxides.
10. The stabilized lithium metal powder according to claim 1,
wherein said powder has a mean diameter of from 10 .mu.m to 200
.mu.m in N-methyl-2-pyrrolidone.
11. The stabilized lithium metal powder according to claim 1,
wherein said powder has a mean diameter of from 10 .mu.m to 200
.mu.m in gamma-butyrolactone.
12. A method of forming a lithium dispersion comprising the steps
of: a) contacting lithium metal powder with a hydrocarbon oil; b)
heating the lithium metal powder and hydrocarbon oil to a
temperature higher than the melting point of the lithium metal
powder; c) subjecting the heated lithium metal powder and
hydrocarbon oil to conditions sufficient to disperse the lithium
metal powder in the oil; and d) contacting the lithium metal powder
with a wax at a temperature between the melting point of the
lithium metal powder and the melting point of the wax.
13. The method of claim 12, wherein the wax has a thickness of 20
nm to 200 nm.
14. The method of claim 12, wherein the hydrocarbon oil is selected
from the group consisting of petroleum oils, shale oils, and
paraffin oils.
15. A method of forming a lithium dispersion comprising the steps
of: a) contacting lithium metal powder with a hydrocarbon oil; b)
heating the lithium metal powder and hydrocarbon oil to a
temperature higher than the melting point of the lithium metal
powder; c) adding a dispersant and a coating reagent; d) subjecting
the heated lithium metal powder and hydrocarbon oil to conditions
sufficient to disperse the lithium metal powder in the oil; and e)
contacting the lithium metal powder with a wax at a temperature
between the melting point of the lithium metal powder and the
melting point of the wax.
16. The method of claim 15, wherein the wax has a thickness of 20
nm to 200 nm.
17. The method of claim 15, further comprising an inorganic
coating.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 60/829,378, filed Oct. 13, 2006, the
disclosure of which is incorporated by reference in its
entirety.
FIELD OF INVENTION
[0002] The present invention relates to stabilized lithium metal
powder ("SLMP") having better stability and a longer storage life.
Such improved SLMP can be used in a wide variety of applications
including organo-metal and polymer synthesis, rechargeable lithium
batteries, and rechargeable lithium ion batteries.
BACKGROUND OF THE INVENTION
[0003] The high surface area of lithium metal can be a deterrent
for its use in a variety of applications because of its pyrophoric
nature. It is known to stabilize lithium metal powder by
passivating the metal powder surface with CO.sub.2 such as
described in U.S. Pat. Nos. 5,567,474, 5,776,369, and 5,976,403,
the disclosures of which are incorporated herein in their
entireties by reference. The CO.sub.2-passivated lithium metal
powder, however, can be used only in air with low moisture levels
for a limited period of time before the lithium metal content
decays because of the reaction of the lithium metal and air. Thus
there remains a need for stable lithium metal with an improved
storage life.
SUMMARY OF THE INVENTION
[0004] The present invention provides a lithium metal powder
protected by a wax. A continuous wax layer provides improved
protection such as compared to, for example, CO.sub.2 passivation.
The resulting lithium metal powder has improved stability and
improved storage life. Furthermore, the wax-protected lithium metal
powder exhibits better stability in N-methyl-2-pyrrolidone (NMP),
which is widely used as a solvent in the electrode fabrication
process in the rechargeable lithium-ion battery industry.
Similarly, the wax-protected lithium metal powder of the invention
exhibits better stability in gamma-butyrolactone (GBL).
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a stability comparison of the wax-coated lithium
metal powder of Example 1 and a CO.sub.2-stabilized lithium metal
powder in dry NMP.
[0006] FIG. 2 is a comparison of the cycle performance of graphite
electrode with wax as an additive and without wax additive.
[0007] FIG. 3 is a side-by-side comparison of ARSST stability test
temperature profiles for the wax-coated lithium metal powder and of
CO.sub.2-coated lithium metal powder in 0.6 percent water-doped
NMP.
[0008] FIG. 4 is a stability comparison of Example 1 and
CO.sub.2-stabilized lithium metal powder in 0.6 percent water-doped
NMP.
[0009] FIG. 5 is an accelerated hygroscopisity tested conducted at
25.degree. C. and 75 percent relative humidity for NMP and GBL.
DETAILED DESCRIPTION OF THE INVENTION
[0010] In the drawings and the following detailed description,
preferred embodiments are described in detail to enable practice of
the invention. Although the invention is described with reference
to these specific embodiments, it will be understood that the
invention is not limited to these embodiments. But to the contrary,
the invention includes numerous alternatives, modifications and
equivalents as will become apparent from consideration of the
following detailed description and accompanying drawing.
[0011] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the term "and/or" includes any and
all combinations of one or more of the associated listed items. As
used herein, the singular forms "a", "an," and "the" are intended
to include the plural forms as well, unless the context clearly
indicates otherwise. It will be further understood that the terms
"comprises" and/or "comprising," when used in this specification,
specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
[0012] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein
[0013] In accordance with the present invention, lithium
dispersions are prepared by heating the lithium metal powder in a
hydrocarbon oil to a temperature above its melting point,
subjecting the lithium metal powder to conditions sufficient to
disperse the molten lithium (e.g., agitating or stirring
vigorously), and contacting the dispersed lithium metal powder with
a wax at a temperature that is between this temperature and the
melting point of the wax. Other alkali metals such as sodium and
potassium can be coated according to the present invention.
[0014] A variety of hydrocarbon oils may be used in the present
invention. The term hydrocarbon oil, as used herein, includes
various oily liquids consisting chiefly or wholly of mixtures of
hydrocarbons and includes mineral oils, i.e., liquid products of
mineral origin having viscosity limits recognized for oils and
hence includes but is not limited to petroleum, shale oils,
paraffin oils and the like. There are many manufacturers of these
useful hydrocarbon oils. Among these useful hydrocarbon oils are
highly refined oils, such as, Peneteck manufactured by Penreco
Division of Pennzoil Products Inc., which has a viscosity in the
range of 43-59 pascal-sec at 100.degree. F. and a flash point of
265.degree. F., Parol 100, which has a viscosity of 213-236
pascal-sec at 100.degree. F. and a flash point of 360.degree. F.
(available from Penreco, Div. of Pennzoil Products), and Carnation
white oil (viscosity=133-165 pascal-sec at 100.degree. F.) made by
Sonneborn Div. of Witco. Even certain purified hydrocarbon solvents
which boil in a range encompassing the melting point of lithium or
sodium metal may be used, such as UNOCAL's 140 Solvent. In
addition, unrefined oils, such as Unocal's 460 Solvent and
Hydrocarbon Seal oil and Exxon's Telura 401 and Telura 407 may also
be used. The selection of a hydrocarbon oil will be within the
skill of one in the art.
[0015] Suitable waxes can be natural wax such as 12-hydroxystearic
acid, synthetic wax such as low molecular weight polyethylene,
petroleum waxes such as paraffin wax, and microcrystalline waxes.
The wax can be introduced to contact the lithium droplets during
the dispersion, or at a lower temperature after the lithium
dispersion has cooled. It is understood that combinations of
different types of waxes with different chemical compositions,
molecular weights, melting points and hardness could be used to
achieve specific coating characteristics for particular
applications. For example, degree of stickiness could be controlled
to allow introduction of the SLMP using a "transfer release paper"
concept, wherein a certain degree of stickiness is required.
[0016] Furthermore, it is beneficial to combine the wax or wax
mixtures of the invention with other inorganic coatings, for
example, Li.sub.2CO.sub.3, LiF, Li.sub.3PO.sub.4, SiO.sub.2,
Li.sub.4SiO.sub.4, LiAlO.sub.2, Li.sub.2TiO.sub.3, LiNbO.sub.3 and
the like, to improve both air stability and polar solvent stability
that would allow both safer handling and possibility of using
commonly used polar solvents that dissolve commonly used polymer
binders. It is recognized that most waxes are soluble in non-polar
solvents at elevated temperatures and solubility at room
temperature is above 0.5%. For example, wax is soluble in NMP at
room temperature at about 0.1% level.
[0017] Suitable waxes described above could produce two types of
coatings on lithium particles: first type representing physical or
adhesive type where non-polar waxes are used and a second type,
representing chemically bonded coatings where waxes with functional
groups, having both hydrophobic and hydrophilic features, are used.
The coating thickness could vary in the range of about 20 nm to
about 200 nm.
[0018] By altering the process parameters and the order of the
reagents addition to the lithium dispersion or lithium dry powder,
the wax-coated lithium metal powder of the invention can have
distinct surface properties. For example, waxes could be introduced
at or below melting point of lithium followed by the addition of
other dispersants above the melting point of lithium, and,
therefore, the wax serves as dispersant/coating reagents. Other
suitable dispersants include oleic acid, linoleic acid, sodium
oleate, lithium oleate, linseed oil, CO.sub.2, N.sub.2, NH.sub.3,
telura oil, stearic acid, oxalic acid, tanic acid, CO, and other
waxes. Waxes or wax mixtures could be introduced above the melting
point of lithium before or after other dispersants and coating
reagents additions, for example the reagents that result in
formation of the coatings such as Li.sub.2CO.sub.3, LiF,
Li.sub.3PO.sub.4, SiO.sub.2, Li.sub.4SiO.sub.4, LiAlO.sub.2,
Li.sub.2TiO.sub.3, and LiNbO.sub.3, and the like, to enhance the
chemical bonding and uniformity of protecting layer by changing the
reaction interfaces. The cooling profile could be used to control
degree of crystallinity and obtain samples with pre-determined
degree of stickiness.
[0019] Alternatively, stabilized lithium metal powder could be
dispersed into the melted non-polar paraffin-like waxes or a
mixture of waxes, and poured into the candle type mold for
crystallization and the concentration of lithium powder could be
calculated as a function of length or volume. Consequently, a piece
of a "candle" could serve as a lithium carrier and used for
organo-metallic and or polymer syntheses; the inert wax could be
extracted with a solvent or allowed to crystallize out and filtered
out upon reaction completion.
[0020] In another embodiment, stabilized lithium metal powder could
be dispersed into the melted non-polar paraffin-like waxes or a
mixture of waxes with mineral oil to form a lithium powder
containing slurry or paste that could be used in a caulk-gun like
apparatus for lithium powder delivery.
[0021] The process produces lithium dispersions having metal
particle sizes in the range of 10 to 500 microns. Moreover, the
tendency of the lithium particles to float to the top of the slurry
is obviated by practice of the present invention. It is recognized
that one skilled in the art will be able to choose the appropriate
particle size depending on the intended use of the lithium
dispersion. On cooling, the resulting lithium dispersions are
readily filtered to remove the bulk of the dispersant hydrocarbon
oil and the metal can then be washed with a solvent such as hexane
to remove residual oil, after which, the metal powder can be dried.
The hydrocarbon oil filtrate is clear and colorless and may be
recycled, without further treatment, to the metal dispersion
process. This is in contrast to the prior art processes which
require clay column purification of the oil before reuse. The dried
metal powders are unexpectedly stable to ambient atmosphere
allowing their safe transfer in such atmospheres from one container
to another.
[0022] Lithium metal used with various embodiments of the present
invention may be provided as lithium powder. The lithium powder may
be treated or otherwise conditioned for stability during
transportation. For instance, dry lithium powder may be formed in
the presence of carbon dioxide as conventionally known. It may be
packaged under an inert atmosphere such as argon. The dry lithium
powder may be used with the various embodiments of the present
invention. Alternatively, the lithium powder may be formed in a
suspension, such as in a suspension of mineral oil solution or
other solvents. Formation of lithium powder in a solvent suspension
may facilitate the production of smaller lithium metal particles,
for example, wherein 100 percent of particles are less than 100
micron. In some embodiments of the present invention, a lithium
powder may be formed in a solvent that may be used with various
embodiments of the present invention. The lithium metal powder
formed in the solvent may be transported in the solvent. Further,
the lithium metal powder and solvent mixture may be used with
embodiments of the present invention, wherein the step of drying
SLMP is eliminated. This may decrease production costs and allow
the use of smaller or finer lithium metal powder particles with the
embodiments of the present invention.
[0023] Alternatively the stabilized lithium metal powder can be
produced by spraying the molten metal through an atomizer nozzle,
and the waxing step can take place after the powder has been
collected. For example, lithium powder could be collected into
lithium compatible solvent containing dry wax or pre-dissolved wax
and the mixture brought to or above the temperature of the clear
point of wax in the solvent, and in one embodiment above the
melting point of lithium. The solvent can be stripped away, using
rotary evaporator, as an example, causing wax to crystallize onto
the lithium particles. Solvents used with embodiments of the
invention must also be non-reactive with the lithium metal and the
binder polymers (binders could be soluble in the solvents
compatible with lithium) at the temperatures used in the anode
production process. Preferably, a solvent or co-solvent possesses
sufficient volatility to readily evaporate from a slurry to promote
the drying of a slurry applied to a current collector. For example,
solvents may include acyclic hydrocarbons and cyclic hydrocarbons
including NMP, GBL, n-hexane, n-heptane, cyclohexane, and the like,
aromatic hydrocarbons, such as toluene, xylene, isopropylbenzene
(cumene), and the like symmetrical, unsymmetrical, and cyclic
ethers, including di-n-butyl ether, methyl t-butyl ether, and the
like.
[0024] In one embodiment, the lithium metal powder protected with
wax coating enables the use of dry NMP solvent.
[0025] The stabilized lithium metal powder can be used in a
secondary battery such as described in U.S. Pat. No. 6,706,447 B2,
the disclosure of which is incorporated by reference in its
entirety. A typical secondary battery comprises a positive
electrode or cathode, a negative electrode or anode, a separator
for separating the positive electrode and the negative electrode,
and an electrolyte in electrochemical communication with the
positive electrode and the negative electrode. The secondary
battery also includes a current collector that is in electrical
contact with the cathode and a current collector that is in
electrical contact with the anode. The current collectors are in
electrical contact with one another through an external circuit.
The secondary battery can have any construction known in the art
such as a "jelly roll" or stacked construction.
[0026] The cathode is formed of an active material, which is
typically combined with a carbonaceous material and a binder
polymer. The active material used in the cathode is preferably a
material that can be lithiated at a useful voltage (e.g., 2.0 to
5.0 V versus lithium). Preferably, non-lithiated materials such as
MnO.sub.2, V.sub.2O.sub.5 or MoS.sub.2, certain transition metal
phosphates, certain transition metal fluorides, or mixtures
thereof, can be used as the active material. However, lithiated
materials such as LiMn.sub.2O.sub.4 that can be further lithiated
can also be used. The non-lithiated active materials are selected
because they generally have higher specific capacities, better
safety, lower cost and broader choice than the lithiated active
materials in this construction and thus can provide increased power
over secondary batteries that use only lithiated active materials.
Furthermore, because the anode includes lithium as discussed below,
it is not necessary that the cathode includes a lithiated material
for the secondary battery to operate. The amount of active material
provided in the cathode is preferably sufficient to accept the
removable lithium metal present in the anode.
[0027] The anode is formed of a host material capable of absorbing
and desorbing lithium in an electrochemical system with the
stabilized lithium metal powder dispersed in the host material. For
example, the lithium present in the anode can intercalate in, alloy
with or be absorbed by the host material when the battery (and
particularly the anode) is recharged. The host material includes
materials capable of absorbing and desorbing lithium in an
electrochemical system such as carbonaceous materials; materials
containing Si, Sn, tin and silicon oxides or composite tin and or
silicon alloys or intermetallics; transition metal oxides such as
cobalt oxide; lithium metal nitrides such as Li.sub.3-xCo.sub.xN
where 0<x<0.5, and lithium metal oxides such as
Li.sub.4Ti.sub.5O.sub.12.
[0028] An alternative use of the stabilized lithium metal powder is
in the preparation of organo lithium products in good yields. The
thin wax layer is believed to not significantly retard reactivity
but does protect the metal from reaction with ambient
atmosphere.
[0029] The following examples are merely illustrative of the
invention, and are not limiting thereon.
EXAMPLES
Comparative Example 1
[0030] Battery grade lithium metal 405 grams was cut into 2.times.2
inch pieces and charged under constant flow of dry argon at room
temperature to a 3 liter stainless steel flask reactor with a 4''
top fitted with a stirring shaft connected to a fixed high speed
stirrer motor. The reactor was equipped with top and bottom heating
mantles. The reactor was then assembled and 1041.4 g of
Peneteck.TM. oil (Penreco, Division of the Penzoil Products
Company) was added. The reactor was then heated to about
200.degree. C. and gentle stirring was maintained in the range of
250 rpm to 800 rpm to ensure all metal was molten, argon flow was
maintained through out the heating step. Then the mixture was
stirred at high speed (up to 10,000 rpm) for 2 minutes. Oleic acid,
8.1 g was charged into the reactor and high speed stirring
continued for another 3 minutes followed by the 5.1 g CO.sub.2
addition. Then the high speed stirring was stopped, heating mantles
removed and dispersion was allowed to cool to about 50.degree. C.
and transferred to the storage bottles. Further, lithium dispersion
was filtered and washed three times with hexane and once with
n-pentane in an enclosed, sintered glass filter funnel to remove
the hydrocarbon oil medium while under argon flow. The funnel was
heated with a heat gun to remove traces of the solvents and the
resulting free-flowing powder was transferred to a tightly capped
storage bottles.
Example 1
[0031] Lithium dispersion in oil, 55.72 grams, (11.275%) containing
6.28 grams of lithium with a medium particle size of 58 micron was
charged into 120 ml hastelloy can equipped with a 1'' Teflon coated
stir bar. The solution was heated to 75.degree. C. and 0.63 grams
of Luwax A (BASF) in a form of 10% solution in p-xylene (Aldrich)
pre-dissolved at 72.degree. C. was added to the lithium dispersion.
This mixture was continuously stirred at 200 rpm for 22 hours.
Sample was allowed to cool to the room temperature and transferred
to the storage bottle. Further, lithium dispersion was filtered and
washed three times with hexane in an enclosed, sintered glass
filter funnel and twice with n-pentane to remove the hydrocarbon
oil medium. The funnel was heated with a heat gun to remove traces
of the solvents and the resulting free-flowing powder was
transferred to a tightly capped storage bottles.
[0032] FIG. 1 shows that no exothermic effects were observed when
Example 1 was mixed at room temperature in dry NMP (<100 ppm
H.sub.2O). Moreover, unlike sample described in Comparative Example
1 that had no metallic lithium left after four days of exposure to
dry NMP solvent, 54 percent metallic lithium was still present in
Example 1. Furthermore, unlike sample described in Comparative
Example 1, wax-coated lithium powder is even stable with NMP with
the amount of moisture of 0.6 percent. FIG. 2 illustrates that when
1 wt % wax is introduced into the battery, (addition is calculated
based on a fully lithiated carbon using 10% wax-coated SLMP) there
are no adverse effects. Half cells of Li/Carbon were tested using
Arbin battery cycler BT-2043. The cells were cycled at 0.50
mA/cm.sup.2 with a potential window of 0.01.about.1.5 V.
[0033] FIG. 3 shows an ARSST (advanced reactive screening system
tool) calorimeter test where samples were exposed to the 0.6
percent water doped NMP under continuous stirring and three days
isothermal hold at room temperature was followed by the 2 days
isothermal hold at 55.degree. C. Runaway reaction was observed for
the CO.sub.2-coated lithium powder at about 48 hours of hold at
room temperature while no exothermic effect was observed for the
wax-coated lithium metal powder of Example 1. Upon completion of
these types of tests, the lithium metallic concentration for the
wax-coated samples is at least 40 percent. FIG. 4 shows the
metallic lithium concentration measured for the wax-coated sample
followed by their exposure to the 0.6 percent water doped NMP over
the period of 10 days at room temperature.
[0034] Solvent hygroscopisity causes quality and performance issues
for the Li-ion batteries (for example, high moisture content might
cause binder polymer to re-crystallize, thus reducing its binding
properties, thus causing electrode film to crack, delaminate, thus
causing failure of the battery). FIG. 5 shows accelerated
hygroscopicity test results conducted at 25.degree. C. and 75
percent relative humidity. For example, while NMP absorbs
.about.0.6 percent of moisture within 7 hours of exposure, GBL
absorbs only 0.23 percent of moisture. This shows that the
wax-coated lithium metal powder is even more stable in GBL.
Example 2
[0035] Lithium dispersion in oil, 780 g, (32.1%) that contained 250
g of lithium with a medium particle size of 63 micron was charged
under constant flow of dry argon at room temperature to a 5 liter
three neck glass flask reactor fitted with a stirring shaft
connected to a fixed high speed stirrer motor. The reactor was
equipped with bottom heating mantles. The reactor was then heated
to about 75.degree. C. and gentle stirring was maintained to ensure
uniform distribution and heat transfer. 25 g of Luwax A (BASF) in a
form of a 10% solution pre-dissolved in p-xylene at 72.degree. C.
was charged into the reactor and stirring continued for another 8
hours. The solution was then cooled slowly and kept at room
temperature while being further stirred for 14 hrs and then
transferred to the storage bottles. Further, lithium dispersion was
filtered and washed three times with hexane in an enclosed,
sintered glass filter funnel and twice with n-pentane to remove the
hydrocarbon oil medium. The funnel was heated with a heat gun to
remove traces of the solvents and the resulting free-flowing powder
was transferred to a tightly capped storage bottles.
[0036] A pyrophoricity test (Method 1050 of DOT regulations for the
transport of spontaneously combustible materials, Code of Federal
Regulations part 173, Appendix E) performed on this material showed
it to be non-pyrophoric.
Example 3
[0037] Lithium dispersion in mineral oil 21.45 grams (27.5%) that
contained 5.90 g of lithium and had medium particle size of 63
microns and 0.62 g Luwax A powder were charged under constant flow
of dry argon at room temperature to a 125 ml glass flask reactor
with a magnetic stirrer bar controlled by super magnetic stirrer.
The reactor was equipped with bottom heating mantle. The reactor
was then heated to the temperature range of 90.degree. C. to
100.degree. C. and stirring was maintained at .about.400 rpm to
ensure uniform distribution and heat transfer for a period of about
1 hour followed by a natural cooling.
Example 4
[0038] Lithium dispersion in mineral oil 21.56 grams (27.5%) that
contained 5.93 g of lithium and had medium particle size of 63
microns and 0.61 g Luwax A powder were charged under constant flow
of dry argon at room temperature to a 125 ml glass flask reactor
with a magnetic stirrer bar controlled by super magnetic stirrer.
Gentle stirring was maintained .about.50 rpm to ensure uniform
distribution and heat transfer before temperature was increased to
90.degree. C. The reactor was equipped with bottom heating mantle.
The reactor was then heated to the temperature range of 90.degree.
C. to 100.degree. C. and then the stirring was increased to
.about.200 rpm, and the mixture was kept under stirring for about
15 minutes. Then, the heating mantle was taken off and the reactor
was allowed to cool naturally.
Example 5
[0039] Lithium dispersion in mineral oil, 21.72 grams (27.5%) that
contained 5.97 g of lithium and had medium particle size of 63
microns was charged under constant flow of dry argon at room
temperature to a 125 ml glass flask reactor with a magnetic stirrer
bar controlled by super magnetic stirrer. Gentle stirring was
maintained at .about.30 rpm to ensure uniform distribution and heat
transfer before temperature was increased to 90.degree. C. The
reactor was equipped with bottom heating mantle. After the reactor
was heated to the temperature of 90.degree. C., 6.55 g (10%)
pre-dissolved Luwax A solution in mineral oil was charged into the
reactor and the stirring increased to 200 rpm. Then the mixture was
kept under stirring for about 15 minutes followed by natural
cooling.
Example 6
[0040] Lithium dispersion in mineral oil, stabilized with the
CO.sub.2-gas, 22.30 grams, (27.5%) that contained 6.13 g of lithium
with medium particle size of 45 microns was charged under constant
flow of dry argon at room temperature to a 125 ml glass flask
reactor with a magnetic stirrer bar controlled by super magnetic
stirrer. Gentle stirring was maintained .about.30 rpm to ensure
uniform distribution and heat transfer before temperature increased
to 90.degree. C. The reactor was equipped with bottom heating
mantle. After the reactor was heated to the temperature of
90.degree. C., 6.52 g pre-dissolved 10% Luwax A solution in mineral
oil was charged into the reactor and the stirring increased to
.about.200 rpm. Then the mixture was kept under stirring for about
15 minutes followed by the natural cooling.
Example 7
[0041] 5 g of dry stabilized lithium metal powder (LectroMax Powder
150, FMC), 75 g p-xylene (Aldrich) and 0.1 g Luwax A powder (BASF)
were charged under constant flow of dry argon at room temperature
to a 200 ml three neck glass flask reactor fitted with a stirring
shaft connected to a fixed high speed stirrer motor. The reactor
was equipped with bottom heating mantles. The reactor was then
heated to about 75.degree. C. and gentle stirring was maintained to
ensure uniform distribution and heat transfer. The mixture was
stirred for 20 minutes at 75.degree. C. and the heating mantle was
then removed to allow the sample to cool rapidly. Further, mixture
was filtered in an enclosed, sintered glass filter funnel. The
sample was dried by passing dry argon through the filter. The
resulting free-flowing powder was transferred to a tightly capped
storage bottles.
Example 8
[0042] Dry stabilized lithium metal powder, 10 g, (LectroMax Powder
150, FMC), 50 g p-xylene (Aldrich) and 0.5 g Luwax A powder (BASF)
were charged in an argon filled glove box at room temperature to a
250 ml round bottom flask. The flask was then attached to a rotary
vacuum solvent extractor (Buchi Rotavapor R110) and partially
submerged in a mineral oil bath at room temperature. The flask was
turned while the mineral oil bath was heated to 80.degree. C. The
temperature of the mixture was maintained at 80.degree. C. with no
vacuum applied for 30 minutes. A vacuum of 25 inches of Hg was then
applied to strip the p-xylene. After 50% of the solvent was
removed, the flask was raised out of the oil bath and allowed to
cool rapidly. The remaining solvent was filtered in an enclosed,
sintered glass filter funnel. The sample was dried by passing dry
argon through the filter. The resulting free-flowing powder was
transferred to a tightly capped storage bottles.
Example 9
[0043] 4924 g of mineral oil and 1364 g of battery grade lithium
metal rods were added to an argon inerted 5 gallon dispersion
apparatus. The mixture was heated to temperature above lithium
melting point under an argon atmosphere with stirring to ensure
that all lithium has melted. The high speed disperser blade was
then started and a mixture of 27 g of oleic acid and 29 g of
mineral oil was introduced into the dispersion pot. After an
additional several minutes of high speed stirring, 18 g of CO.sub.2
carbon dioxide gas was introduced. After this, the high speed
stirring was brought down to minimum speed and reaction mixture
cooled down to 105.degree. C. with external cooling. 136 g of Luwax
A powder (BASF) was introduced and the temperature was maintained
above 95.degree. C. for the next 15 minutes followed by cooling to
ambient temperature. The wax coated SLMP dispersion was then
transferred out of the pot. A sample of the dispersion was washed
with hexane and pentane to remove the mineral oil. The material was
then dried under argon.
Example 10
[0044] Dry stabilized lithium metal powder, 10 g, (LectroMax Powder
150, FMC), 50 g p-xylene (Aldrich) and 0.5 g Luwax A powder (BASF)
were charged in an argon filled glove box at room temperature to a
250 ml round bottom flask. The flask was then attached to a rotary
vacuum solvent extractor (Buchi Rotavapor R110) and partially
submerged in a mineral oil bath at room temperature. The flask was
turned while the mineral oil bath was heated to 80.degree. C. The
temperature of the mixture was maintained at 80.degree. C. with no
vacuum applied for 30 minutes. A vacuum of 25 inches of Hg was then
applied to strip the p-xylene. As the sample began to dry the
vacuum was lowered to 30 inches of Hg to remove the remaining
solvent. The flask was removed from the rotary evaporator and the
sample was further dried by passing dry argon through the flask.
The resulting powder was transferred to a tightly capped storage
bottles.
Example 11
[0045] Battery grade lithium metal 4427 g and 15345 g of mineral
oil were added to a 15 gallon dispersion pot. The mixture was
heated to the temperature above the melting point of lithium metal
while stirring. Then the high speed disperser blade was set into
motion at 4800 rpm and a mixture of 90 gm of oleic acid and 90 g of
mineral oil was introduced in to the dispersion pot. After several
minutes of high speed dispersion, 58 g of carbon dioxide gas was
introduced in to the pot and allowed to react with the metal
particles. The high speed disperser was shut off shortly after
CO.sub.2 addition and cold mineral oil was added to the mix to
bring the temperature of the dispersion below the melting point of
lithium metal. Anchor agitator was used to continue stirring the
dispersion mixture until the material was cooled down to the room
temperature to promote uniformity of the suspension. External
cooling was applied to the system. The material was discharged and
analyzed. The mean diameter of the stabilized lithium dispersion
was 52 micron.
Example 12
[0046] Battery grade lithium metal 44137 g and 15436 g of mineral
oil were added to a 15 gallon dispersion pot. The mixture was
heated to the temperature above the melting point of lithium metal
under continuous stirring. Then the high speed disperser blade was
set into motion at 4800 rpm and a mixture of 89 gm of oleic acid
and 87 g of mineral oil was introduced into the dispersion pot.
After several minutes of high speed dispersion, 57 g of carbon
dioxide gas was charged into the pot and allowed to react with the
metal particles. Upon completion of the reaction, 118 g of Luwax S
was introduced into the pot. After additional high speed mixing the
high speed disperser was shut off and cold mineral oil was added to
the mix to bring the temperature below the melting point of lithium
metal. Anchor agitator was used to continue stirring the dispersion
mixture until the material was cooled down to the room temperature
to promote uniformity of the suspension. External cooling was
applied to the system. The material was discharged and analyzed.
The mean diameter of the stabilized lithium dispersion was 40
micron.
[0047] These two examples and figures demonstrate that wax could be
used both as a coating reagent and as a dispersant reagent. This is
a very important property that could be used in designing products
with reduced particle size/increased surface area for specific
applications, for example spraying SLMP powder in the solvent
solution onto the electrode surfaces or continuously introducing
dry SLMP powder into the Tokamak edge using the "gun"-like devices
to increase plasma stability and electron temperatures and reduce
the impurity levels (lithium is a getter). Table 1 below summarizes
specific process conditions and particle size results.
TABLE-US-00001 TABLE 1 Process conditions and experimental results
for examples 11 and 12 Oleic Dispersing Stabilizing D50 acid, %
Speed RPM Additives micron Example 11 2% 4800 1.25% CO2 52 Example
12 2% 4800 1.25% CO2 & 2.5% 40 Luwax S
[0048] Having thus described certain embodiments of the present
invention, it is to be understood that the invention defined by the
appended claims is not to be limited by particular details set
forth in the above description as many apparent variations thereof
are possible without departing from the spirit or scope thereof as
hereinafter claimed. The following claims are provided to ensure
that the present application meets all statutory requirements as a
priority application in all jurisdictions and shall not be
construed as setting forth the full scope of the present
invention.
* * * * *