U.S. patent application number 12/465865 was filed with the patent office on 2010-11-18 for method of making an alloy.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Dinh B. Le.
Application Number | 20100288077 12/465865 |
Document ID | / |
Family ID | 42111705 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100288077 |
Kind Code |
A1 |
Le; Dinh B. |
November 18, 2010 |
METHOD OF MAKING AN ALLOY
Abstract
A method of making an alloy comprises alloying components
comprising: ferrosilicon having a ratio of iron to silicon; and at
least one of a metallic element or a metallic compound. The alloy
may be used in electrode compositions for lithium ion
batteries.
Inventors: |
Le; Dinh B.; (St. Paul,
MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
42111705 |
Appl. No.: |
12/465865 |
Filed: |
May 14, 2009 |
Current U.S.
Class: |
75/392 |
Current CPC
Class: |
C22C 1/02 20130101; B82Y
30/00 20130101; H01M 10/0525 20130101; B22F 2999/00 20130101; Y02E
60/10 20130101; H01M 4/364 20130101; B22F 3/006 20130101; H01M
4/134 20130101; H01M 4/587 20130101; H01M 4/38 20130101; H01M
2004/021 20130101; B22F 2999/00 20130101; B22F 3/006 20130101; B22F
9/04 20130101 |
Class at
Publication: |
75/392 |
International
Class: |
C22C 33/00 20060101
C22C033/00 |
Claims
1. A method of making an alloy, the method comprising alloying
components comprising: a first ferrosilicon having a first ratio of
iron to silicon; and at least one of a metallic element or a
metallic compound, wherein the alloy is substantially free of
crystallites greater than 50 nanometers in size.
2. The method of claim 1, wherein said metallic element or metallic
compound comprises at least one of carbon, tin, titanium, zinc,
iron, or silicon.
3. The method of claim 1, wherein the alloy is amorphous.
4. The method of claim 1, wherein alloying comprises milling using
milling media.
5. The method of claim 1, wherein the alloy comprises tin, iron,
and silicon.
6. The method of claim 1, wherein the alloy comprises tin, iron,
and carbon.
7. The method of claim 1, wherein the metallic compound comprises a
second ferrosilicon having a second ratio of iron to silicon, and
wherein the first ratio and the second ratio are different.
8. The method of claim 7, wherein the components further comprise
tin.
9. The method of claim 7, wherein the components further comprise
titanium.
10. The method of claim 1, wherein the alloy is adapted for use as
an active material in a negative electrode composition in a lithium
ion battery.
11. The method of claim 10, wherein said metallic element or
metallic compound comprises at least one of carbon, tin, titanium,
zinc, iron, or silicon.
12. The method of claim 10, wherein the alloy is amorphous.
13. The method of claim 10, wherein alloying comprises milling
using milling media.
14. The method of claim 10, wherein the alloy comprises tin, iron,
and silicon.
15. The method of claim 10, wherein the alloy comprises tin, iron,
and carbon.
16. The method of claim 10, wherein the components further comprise
a second ferrosilicon having a second ratio of iron to silicon, and
wherein the first ratio and the second ratio are different.
17. The method of claim 16, wherein the components further comprise
tin.
18. The method of claim 16, wherein the components further comprise
titanium.
Description
TECHNICAL FIELD
[0001] The present disclosure broadly relates to methods for making
metallic alloys.
BACKGROUND
[0002] Metallic alloys are used in negative electrodes for lithium
ion batteries. Negative electrodes containing such metal alloys
generally exhibit higher capacities relative to intercalation-type
anodes such as graphite. Typically, silicon-containing alloys are
made directly from the respective component elements; for example,
by a milling process.
[0003] Alloys containing Fe, Si, Sn, and/or C are useful, for
example, as active materials for use as a negative electrode
material for a lithium ion battery. Small grain sizes of individual
phases in such alloys are typically important for good performance
as an active electrode material (i.e., reversible
lithiation/delithiation). This can typically be achieved by rapid
quenching (e.g., melt spinning or sputtering), or milling (e.g.,
mechanical alloying).
[0004] Current common practice in the industry uses powdered
purified elemental metals as raw materials to fabricate active
electrode materials using processes that are typically laborious,
time-consuming, and/or costly.
SUMMARY
[0005] In one aspect, the present disclosure provides a method of
making an alloy, the method comprising alloying components
comprising:
[0006] a first ferrosilicon having a first ratio of iron to
silicon; and
[0007] at least one of a metallic element or a metallic compound,
wherein the alloy is substantially free of crystallites greater
than 50 nanometers in size. Alloys prepared according to the
present disclosure may be suitable for use as a negative electrode
material in a lithium ion battery.
[0008] In some embodiments, the metallic element or metallic
compound comprises at least one of carbon, tin, titanium, zinc,
iron, or silicon. In some embodiments, the alloy is amorphous. In
some embodiments, alloying comprises milling using milling media.
In some embodiments, the alloy comprises tin, iron, and silicon. In
some embodiments, the alloy comprises tin, iron, and carbon.
[0009] In some embodiments, the metallic compound comprises a
second ferrosilicon having a second ratio of iron to silicon, and
wherein the first ratio and the second ratio are different.
[0010] Advantageously, alloys prepared according to the present
disclosure can typically be prepared easier, faster, and less
expensively than with conventional processes that use pure forms of
the components used to make the alloy. In part, this is because
some grades of ferrosilicon (e.g., iron containing 50, 75, and 90
percent by weight of silicon) are commercially available by the ton
at relatively low prices. Many different grades of ferrosilicon are
readily available commercially.
[0011] As used herein:
[0012] the term "alloy" refers to a substance having one or more
metallic phases, and comprising two or more metallic elements;
[0013] the term "alloying" refers to a process that forms an
alloy;
[0014] the term "delithiation" refer to a process for removing
lithium from an electrode material;
[0015] the term "metallic" means of, relating to, or having the
characteristics of a metal;
[0016] the term "metallic compound" refers to compounds that
include at least one metallic element;
[0017] the term "metallic element" refers to all elemental metals
(including tin), silicon, and carbon;
[0018] the term "mill" refers to a device for alloying, grinding,
pulverizing, or otherwise breaking down a material into small
particles (examples include pebble mills, jet mills, ball mills,
rod mills and attritor mills);
[0019] the term "milling" refers to a process of placing a material
in a mill and operating the mill to perform alloying, or to grind,
pulverize, or break down the material into small or smaller
particles; and
[0020] the term "negative electrode" refers to an electrode of a
lithium ion battery (often called an anode) where electrochemical
oxidation and delithiation occurs during a discharging process.
DETAILED DESCRIPTION
[0021] Ferrosilicon is a metallic alloy of iron and silicon
commonly prepared by fusing iron and silica in the presence of
carbon in an electric furnace. It is of considerable importance in
the manufacture of steel and cast iron. Accordingly, ferrosilicon
is available commercially in various weight ratios of iron to
silicon covering essentially the entire compositional range.
Examples include 0.1:99, 1:99, 5:95, 10:90, 20:80, 30:70, 40:60,
50:50, 60:40, 70:30, 80:20, 90:10, 95:5, 99.9:0.1, although other
ratios may also be used. Ferrosilicon with the compositions 50:50
(Fe:Si by weight) and 25:75 (Fe:Si by weight) are widely available
in tonnage quantities, and at commodity prices that may be less
that the constituent purified metallic elements (i.e., iron and
silicon).
[0022] According to the present disclosure, at least one
ferrosilicon is alloyed with at least one metallic element and/or
metallic alloy. The metallic alloy may be any metallic alloy; for
example, a ferrosilicon, an alloy of silicon and tin, or an alloy
of carbon and iron. In those embodiments of the present disclosure
using two compositionally different ferrosilicon alloys, it is
possible to achieve any compositional ratio of iron to silicon that
falls between the compositional ratios of the two ferrosilicon
alloys. For example, using 50:50 Fe:Si and 25:75 Fe:Si ferrosilicon
alloys, it is possible to achieve all compositional ranges between
50 and 75 percent silicon by blending appropriate amounts of each.
For values lying outside the corresponding range, pure elemental
iron or silicon may be added in an amount that achieves a desired
stoichiometry.
[0023] Additional metallic elements and metallic alloys may
optionally be incorporated in processes according to the present
disclosure, may be readily obtained from commercial sources.
Examples include carbon, silicon, tin, and transition metals (e.g.,
Fe, Ti, Y, V, Cu, Zr, Zn, Co, Mn, Mo, and Ni), and alloys thereof,
although other metallic elements and metallic alloys may also be
used.
[0024] Alloying may be conducted thermally; for example, in an
electric arc furnace. Alloying may also be accomplished by
mechanical methods such as, for example, milling. The alloying
process may use ingot, chunk, powder, or other forms of
ferrosilicon and optional metallic components to be included in
that alloy.
[0025] Milling techniques are generally useful for mechanically
alloying metallic elements and/or metallic alloys; especially as
powders. Examples of suitable milling techniques include jet
milling, ball milling (e.g., using a planetary mill, vibrational
mill, attritor mill, or a cylindrical or conical vessel). Jet mills
abrade particles by impinging them against hard target substrates.
Ball mills contain milling media that serve to grind material
placed in the mill. Examples of suitable milling media include
steel, porcelain, and/or ceramic media, which may be in the form of
rods, balls, or other shapes. In general, the process conditions
will vary with the type of milling technique used, and will be
apparent to those of ordinary skill in the milling art.
[0026] In general, milling should be conducted in a controlled
oxygen environment; for example, in an inert gas (e.g., nitrogen,
helium, and/or argon) environment. In general, the use of preformed
metallic alloys significantly reduces the processing time required
for forming desired alloys as compared to using pure metallic
elements. For example, methods according to the present disclosure
are especially useful for mechanically alloying metallic element
powders and/or metallic alloy powders.
[0027] Mechanically alloyed compositions prepared according to the
present disclosure are useful, for example, for forming electrode
compositions (e.g., negative electrode compositions) for use in
lithium ion batteries.
[0028] It may be desirable to use milling conditions that result in
few if any crystallites of significant size being present in the
resultant alloy. For example, the resultant alloy may be formed
such that it is substantially free of crystallites greater than 50
nanometers in size (i.e., the maximum dimension of each
crystallite). The resultant alloy may contain less than 5 percent
by volume, less than one percent by volume, or even less than 0.1
percent by volume of crystallites greater than 50 nanometers in
size. In some embodiments, the resultant alloy may be formed as an
amorphous composition.
[0029] One desirable method of mechanically alloying metallic
elements and/or metallic alloys is described in U.S. application
Ser. No. ______, entitled "LOW ENERGY MILLING METHOD, ALLOY, AND
NEGATIVE ELECTRODE COMPOSITION" (Attorney Docket No. 65465US002),
filed contemporaneously herewith.
[0030] Exemplary alloys include silicon alloys wherein the active
material comprises from about 50 to about 85 mole percent silicon,
from about 5 to about 25 mole percent iron, from about 0 to about
12 mole percent titanium, and from about 0 to about 12 mole percent
carbon. Exemplary alloys of silicon, iron and additional elements
may be found in, for example,
[0031] U.S. Pat. Appl. Publ. Nos. 2005/0031957 A1 (Christensen et
al), 2007/0020521 A1 (Obrovac et al.), and 2007/0020522 A1 (Obrovac
et al.).
[0032] If mechanical alloying is used, a milling aid may optionally
be added to the metallic components being alloyed. Examples of
milling aids include one or more saturated higher fatty acids
(e.g., stearic acid, lauric acid, and palmitic acid) and salts
thereof, hydrocarbons such as mineral oil, dodecane, polyethylene
powder. In general the amount of any optional milling aid is less
than 5 percent, typically less than 1 percent of the millbase.
[0033] Objects and advantages of this disclosure are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this disclosure.
EXAMPLES
[0034] Unless otherwise noted, all parts, percentages, ratios, etc.
in the Examples and the rest of the specification are by
weight.
[0035] The following Abbreviations are used in the Examples.
TABLE-US-00001 ABBRE- VIATION DESCRIPTION DEC Diethyl carbonate
from Ferro Corp. EC Ethylene carbonate from Ferro Corp., Zachary,
LA Fe1 Iron pieces having irregular shape with a size 12 mm or
less, 99.97 percent pure, available from Alfa Aesar. FEC
Fluoroethylene carbonate from Fujian Chuangxin Science and Develops
Co., LTD, Fujian, China FerroSi50 Ferrosilicon containing 47.92
percent of silicon and 51.35 percent of iron available from Globe
Metallurgical, Inc. Crushed and sized to less than 500 micrometers.
FerroSi75 Ferrosilicon containing 73.53 percent of silicon and
24.88 percent by weight of iron available from Globe Metallurgical,
Inc., Beverly, OH. Crushed and sized to less than 500 micrometers.
Graphite1 A graphite powder available as TIMREX SFG44 from TIMCAL
Ltd., Bodio, Switzerland. Graphite2 A graphite powder with an
average particle size of 24.4 micrometers and a 3.2 m.sup.2/g BET
surface area available as MAGE from Hitachi Chemical Co. Ltd.,
Tokyo, Japan LiOH-20 A 20 percent solution of lithium hydroxide in
water, prepared from LiOH--H.sub.2O and deionized water.
LiOH--H.sub.2O Lithium hydroxide monohydrate, 98+%, A.C.S. Reagent
available from Sigma-Aldrich Co, St. Louis, MO. PAA-34 A
polyacrylic acid solution having a weight average molecular weight
of 250,000 g/mole available as a 34 percent solution in water from
Sigma-Aldrich Co. PAA-Li A 10 percent polyacrylic acid - lithium
salt solution in water prepared by titrating PAA-34 with LiOH-20
until fully neutralized and adding deionized water to obtain the
desired 10 percent concentration. Si1 Silicon pieces with a size of
10 cm or less, 98.4 percent pure, available from Alfa Aesar, Ward
Hill, MA. Sn1 325 mesh tin powder, 99.8 percent pure, available
from Alfa Aesar. Ti1 325 mesh titanium powder, 99.5 percent pure,
available from Alfa Aesar.
X-Ray Measurement
[0036] X-ray diffraction patterns were collected using a Siemens
Model KRISTALLOFLEX 805 D500 diffractometer equipped with a copper
target x-ray tube and a diffracted beam monochromator. The X-ray
diffraction patterns were collected using scattering angles between
20 and 60 degrees [two-theta] stepped at 0.05 degrees [two-theta].
The crystalline domain size was calculated from the width of x-ray
diffraction peaks using the Scherrer equation.
Comparative Example A
[0037] Large grain SiFe alloy was prepared by arc melting 120.277
grams (g) of Si1 and 79.723 g of Fe1. The Si.sub.75Fe.sub.25 ingot,
containing about 75 mole percent silicon and 25 mole percent iron,
was crushed and sized to less than 150 micrometers. The Si/Fe large
grain alloy powder (120 g), was placed in the 5 liter, steel
chamber of a ball mill (Model 611, Jar size 1 available from U.S.
Stoneware, Ohio). The chamber was cylindrical in shape with an
internal diameter of about 18.8 cm (7.4 inch) and a length of about
17.1 cm (6.75 inch). In addition to the large grain alloy powder,
10 kg of 1.27 cm (0.5 inch) diameter chromium steel balls, one
cylindrical steel bar 23.2 cm (9.125 inch) length.times.1.27 cm
(0.5 inch) diameter and two cylindrical steel bars 21.5 cm (8.625
inch) length.times.1.27 cm (0.5 inch) diameter were added to the
chamber. The chamber was purged with N.sub.2 and milled at 85 rpm
(revolutions per minute) for 6 days. After milling, a Si/Fe powder
alloy containing about 75 mole percent silicon and 25 mole percent
iron was produced (Powder A).
[0038] An X-ray diffraction pattern of the Si.sub.75Fe.sub.25 alloy
ingot showed crystalline Si and crystalline FeSi.sub.2. An X-ray
diffraction pattern of Powder A showed nanostructures with small
grain size for the FeSi.sub.2 phase and a virtually amorphous Si
phase. The term "amorphous" is used in the Examples to describe
materials that have no defined X-ray diffraction peak indicative of
a crystalline phase.
Example 1
[0039] FerroSi75 (59.27 g) and FerroSi50 (72.15 g) were milled used
the procedure described in Comparative Example A, except the
milling time was 7 days. After milling, a Si/Fe alloy powder
containing about 75 mole percent silicon and 25 mole percent iron
was produced, Powder 1. The X-ray diffraction pattern of the
starting FerroSi75 showed peaks characteristic of crystalline Si
and FeSi.sub.2 phases. The X-ray diffraction pattern of the
starting FerroSi50 showed peaks characteristic of crystalline
FeSi.sub.2 phases with small trace of crystalline Si. The x-ray
diffraction pattern of Powder 1 showed peaks characteristic of
nanocrystalline FeSi.sub.2 having a grain size less than 50 nm. The
X-ray diffraction pattern of Powder 1 did not contain peaks from
Si, indicating that the Si phase in the ball milled alloy was
amorphous.
Example 2
[0040] FerroSi75 (83.74 g), 45.55 g of FerroSi50, and 2.38 g of
Graphite1 were milled using the procedure described in Comparative
Example A, except the milling time was 9 days. After milling, a
Si/Fe/C alloy powder containing about 75 mole percent silicon, 20
mole percent iron and 5 mole percent carbon was produced, Powder 2.
The X-ray diffraction pattern of Powder 2, showed peaks
characteristic of nanocrystalline FeSi.sub.2 with a grain size less
than 50 nm. The X-ray diffraction pattern of Powder 2 did not
contain peaks from Si, indicating that the Si phase in the alloy
was amorphous. From stoichiometry, this alloy also contained a SiC
phase, however, the X-ray diffraction pattern of the ball milled
alloy did not contain peaks from SiC, indicating that this phase
was amorphous.
Example 3
[0041] FerroSi75 (111.70 g), 15.08 g of FerroSi50, and 5.10 g of
Graphite1 were milled using the procedure described in Example 2.
After milling, a Si/Fe/C alloy powder containing about 75 mole
percent silicon, 15 mole percent iron and 10 mole percent carbon
was produced, Powder 3. The x-ray diffraction pattern of Powder 3
showed peaks characteristic of nanocrystalline FeSi.sub.2 with a
grain size less than 50 nm. The x-ray diffraction pattern of Powder
3 did not contain peaks from Si, indicating that the Si phase in
the alloy was amorphous. From stoichiometry, this alloy also
contained a SiC phase, however, the X-ray diffraction pattern of
the alloy did not contain peaks from SiC, indicating that this
phase was amorphous.
Example 4
[0042] FerroSi75 (46.21 g), 69.06 g of FerroSi50, and 15.97 g of
Sn1 were milled using the procedure described in Comparative
Example A. After milling, a Si/Fe/Sn alloy powder containing about
71 mole percent silicon, 25 mole percent iron and 4 mole percent
tin was produced, Powder 4. The X-ray diffraction pattern of Powder
4 showed peaks characteristic of nanocrystalline FeSi.sub.2 with a
grain size less than 50 nm. The x-ray diffraction pattern of Powder
4 did not contain peaks from Si and Sn, indicating that the Si and
Sn phases in the ball milled alloy were amorphous.
Example 5
[0043] FerroSi75 (46.02 g), 62.82 g of FerroSi50, 16.89 g of Sn1,
and 4.27 g of Graphite 1 were placed in the chamber of the ball
mill described in Comparative Example A. Milling used the procedure
described in Comparative Example A. After milling, a Si/Fe/Sn/C
alloy powder containing about 64 mole percent silicon, 22 mole
percent iron, 4 mole percent tin and 10 mole percent carbon was
produced, Powder 5. The X-ray diffraction pattern of Powder 5
showed peaks characteristic of nanocrystalline FeSi.sub.2 with a
grain size less than 50 nm. The X-ray diffraction pattern of Powder
5 did not contain peaks from Si, Sn and SiC, indicating that the
Si, Sn and SiC phases in the alloy were amorphous.
Example 6
[0044] FerroSi75 (64.29 g), 42.77 g of FerroSi50, 16.14 g of Sn1,
and 8.14 g of Ti1 were milled using the procedure described in
Comparative Example A, except the milling time was 13 days. After
milling, a Si/Fe/Sn/Ti alloy powder containing about 71 mole
percent silicon, 20 mole percent iron, 4 mole percent tin and 5
mole percent titanium was produced, Powder 6. The X-ray diffraction
pattern of Powder 6, showed peaks characteristic of nanocrystalline
FeSi.sub.2 with a grain size less than 50 nm. The X-ray diffraction
pattern of Powder 6 did not contain peaks from Si, Sn and
TiSi.sub.2 (and/or FeTiSi.sub.2), indicating that the Si, Sn and
TiSi.sub.2 (and/or FeTiSi.sub.2) phase alloy were amorphous.
Example 7
[0045] FerroSi75 (1.27 g), 0.69 g of FerroSi50, and 0.04 g of
Graphite1 were placed in a 45-milliliter tungsten carbide chamber,
Model 8001 from Spex Certiprep Ltd., Metuchen, N.J. In addition to
the powder, 28 tungsten carbide balls (about 108 g) having a 0.79
cm (0.3125 inch) diameter were added to the chamber. The chamber
was placed in a dual mixer/mill, Model 8000-D from Spex Certiprep
Ltd. The chamber was vibrated by the dual mixer/mill for two hours.
The vessel was cooled with an air jet during the two hour milling
period, maintaining a chamber temperature of about 30.degree. C.
After milling, a Si/Fe/C alloy powder containing about 75 mole
percent silicon, 20 mole percent iron, and 5 mole percent carbon
was produced, Powder 7. The x-ray diffraction pattern of Powder 7
showed peaks characteristic of nanocrystalline Si and FeSi.sub.2
with a grain size 6 nm and 12 nm, respectively. From stoichiometry,
this alloy also contained SiC phases, however, the X-ray
diffraction pattern of Powder 7 did not contain peaks from SiC,
indicating that this phase was amorphous.
Example 8
[0046] FerroSi75, 1.70 g, and FerroSi50, 0.23 g and 0.08 g Graphite
1 were milled using the procedure described in Example 7. After
milling, a Si/Fe/C alloy powder containing about 75 mole percent
silicon, 15 mole percent iron and 10 mole percent carbon was
produced, Powder 8. The x-ray diffraction pattern of Powder 8
showed peaks characteristic of nanocrystalline Si and FeSi.sub.2
with a grain size of 11 nm and 12 nm, respectively. From
stoichiometry, this alloy also contained a SiC phase, however, the
X-ray diffraction pattern of Powder 8 did not contain peaks from
SiC, indicating that this phase was amorphous.
Procedure for Preparing an Alloy Electrode, Cell Assembly and Cell
Testing
[0047] Alloy powder (1.84 g) and 1.6 g of PAA-Li were mixed in a
45-milliliter stainless steel vessel using four, 1.27 cm (0.5 inch)
tungsten carbide balls. The mixing was done in a Planetary Micro
Mill Pulverisette 7 from Fritsch, Germany at speed 2 for one hour.
The resulting solution was hand spread onto a 10-micrometer thick
Cu foil using a gap die (typically 3 mil gap). The sample was then
dried in a vacuum oven at 120.degree. C. for 1-2 hours producing an
alloy electrode film. Circles, 16 mm in diameter, were then punched
out of the alloy electrode film and were used as an alloy electrode
for a cell (below).
[0048] Half coin cells were prepared using 2325 button cells. All
of the components were dried prior to assembly and the cell
preparations were done in a dry room with a -70.degree. C. dew
point. The cells were constructed from the following components and
in the following order, from the bottom up. Cu Spacer/Li metal
film/Separator/alloy electrode/Cu spacer. Each cell consisted of a
20 mm diameter.times.0.762 mm (30 mil) thick disk of Cu spacer, a
16 mm diameter disk of alloy electrode, a 20 mm diameter micro
porous separators (CELGAR2400p available from Separation Products,
Hoechst Celanese Corp., Charlotte, N.C.), 18 mm diameter.times.0.38
mm thick disk of Li metal film (lithium ribbon available from
Aldrich Chemical Co., Milwaukee, Wis.) and a 20 mm
diameter.times.0.762 mm (30 mil) disk of copper spacer. The
electrolyte was a solution containing 90 percent by weight of an
EC/DEC solution (2/1 by volume) and 10 percent by weight FEC with
LiPF.sub.6 used as the conducting salt at a 1 M concentration.
Prior to adding the LiPF.sub.6, the mixture was dried over
molecular sieve (3A type) for 12 hours. The cell was filled with
100 microliters of electrolyte solution. The cell was crimp sealed
prior to testing.
[0049] Cells were cycled from 0.005V to 0.90V at specific rate of
100 mA/g-alloy with trickle down to 10 mA/g at the end of discharge
(delithiation) for the first cycle. From then on, cells were cycled
in the same voltage range but at 200 mA/g-alloy and trickle down to
20 mA/g-alloy at the end of discharge. Cells were allowed 15 min
rest at open circuit at the end of every half cycle.
Example 9
[0050] An alloy electrode film and three coin cells were prepared
and tested according to the Procedure for Preparing an Alloy
Electrode, Cell Assembly and Cell Testing using Powder 1. Results
are reported Table 1.
Example 10
[0051] An alloy electrode film and three coin cells were prepared
and tested according to the Procedure for Preparing an Alloy
Electrode, Cell Assembly and Cell Testing using Powder 4. Results
are reported Table 1.
Example 11
[0052] An alloy electrode film and three coin cells were prepared
and tested according to the Procedure for Preparing an Alloy
Electrode, Cell Assembly and Cell Testing using Powder 5. Results
are reported Table 1.
Example 12
[0053] An alloy electrode film and three coin cells were prepared
and tested according to the Procedure for Preparing an Alloy
Electrode, Cell Assembly and Cell Testing using Powder 6. Results
are reported Table 1.
Example 13
[0054] An alloy electrode film was prepared using Powder 4. Powder
4 was first sized by milling in heptane. Powder 4 (4 g) and 20 g of
heptane were placed in a 45-milliliter stainless steel vessel
containing 17.62 g of 9.5 mm (0.375 inch) diameter chromium steel
balls and 22.98 g of 6.35 mm (0.25 inch) diameter chromium steel
balls. The milling was done in a Planetary Micro Mill Pulverisette
7 at a speed 5 for one hour. Excess heptane was removed, and the
wet sample was dried at 80.degree. C. for 1 hour. An alloy
electrode film was prepared from the sized powder in the following
manner. Sized Powder 4 (0.96 g), 0.96 g of Graphite2, 0.8 g of
PAA-Li, and 4.5 g of deionized water, were mixed in a 45-milliliter
stainless steel vessel using four 12.7 mm (0.5 inch) diameter
tungsten carbide balls. The mixing was done in the Planetary Micro
Mill Pulverisette 7 at speed 2 for one hour. The resulting solution
was hand spread onto a 10-micrometer thick Cu foil using an 8-mil
gap die. The sample was air dried, then calendered and dried in a
vacuum oven at 120.degree. C. for 1 hour. Circles, 16 mm in
diameter, were then punched out of the alloy electrode film and
were used as an alloy electrode for a cell. Three coin cells were
prepared according to the second paragraph of the Procedure for
Preparing an Alloy Electrode, Cell Assembly and Cell Testing. The
cells were cycled from 0.005 V to 0.90 V at specific rate of 75
mA/g-alloy with trickle down to 7.5 mA/g at the end of discharge
(delithiation) for the first cycle. From then on, cells were cycled
in the same voltage range but at 150 mA/g-alloy and trickle down to
15 mA/g-alloy at the end of discharge. Cells were allowed 15 min
rest at open circuit at the end of every half cycle. Results are
reported in Table 1 (below).
TABLE-US-00002 TABLE 1 Initial Capacity Capacity at Capacity at
Loss, Cycle 2, Cycle 50, Efficiency Example percent mAh/g mAh/g
percent 9 11 912 895 98 10 13 818 763 93 11 13 861 752 87 12 14 875
865 99 13 16 554 544 98 In Table 1 (above), Efficiency = Capacity
at Cycle 50/Capacity at Cycle 2.
[0055] Overall, the alloy powders prepared according to the present
disclosure, when fabricated into an electrode and further
fabricated into a cell, showed stable capacity for many cycles,
making them suitable for use as active anode materials in battery
applications, including rechargeable lithium ion battery
applications.
[0056] All patents and publications referred to herein are hereby
incorporated by reference in their entirety. All examples given
herein are to be considered non-limiting unless otherwise
indicated. Various modifications and alterations of this disclosure
may be made by those skilled in the art without departing from the
scope and spirit of this disclosure, and it should be understood
that this disclosure is not to be unduly limited to the
illustrative embodiments set forth herein.
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