U.S. patent application number 13/718848 was filed with the patent office on 2013-05-16 for lithium-based compound nanoparticle compositions and methods of forming the same.
This patent application is currently assigned to Primet Precision Materials, Inc.. The applicant listed for this patent is Primet Precision Materials, Inc.. Invention is credited to Robert J. Dobbs, Archit Lal.
Application Number | 20130122300 13/718848 |
Document ID | / |
Family ID | 38459689 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130122300 |
Kind Code |
A1 |
Dobbs; Robert J. ; et
al. |
May 16, 2013 |
LITHIUM-BASED COMPOUND NANOPARTICLE COMPOSITIONS AND METHODS OF
FORMING THE SAME
Abstract
Lithium-based compound small particle compositions, as well as
methods and structures associated with the same, are provided. The
particle compositions, in some cases, are characterized by having
an nano-size particles. The particle compositions may be produced
in a milling process. In some embodiments, the particles may be
coated with a coating that may enhance certain properties of the
particle composition (e.g., electrical conductivity).
Inventors: |
Dobbs; Robert J.; (Newfield,
NY) ; Lal; Archit; (Ithaca, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Primet Precision Materials, Inc.; |
Ithaca |
NY |
US |
|
|
Assignee: |
Primet Precision Materials,
Inc.
Ithaca
NY
|
Family ID: |
38459689 |
Appl. No.: |
13/718848 |
Filed: |
December 18, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11712831 |
Feb 28, 2007 |
8377509 |
|
|
13718848 |
|
|
|
|
60778029 |
Feb 28, 2006 |
|
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Current U.S.
Class: |
428/402 ; 241/22;
241/3; 241/30; 977/773 |
Current CPC
Class: |
C01P 2006/12 20130101;
C01G 1/00 20130101; C04B 35/62839 20130101; C04B 2235/5409
20130101; C04B 35/62665 20130101; C04B 35/62892 20130101; C04B
2235/3262 20130101; C04B 2235/447 20130101; H01M 4/587 20130101;
B02C 19/0056 20130101; H01M 2004/021 20130101; B82Y 30/00 20130101;
C04B 2235/3234 20130101; H01M 4/366 20130101; Y10T 428/2982
20150115; B02C 19/186 20130101; B32B 5/16 20130101; Y02E 60/10
20130101; B02C 17/00 20130101; Y10T 428/2991 20150115; C04B
2235/3203 20130101; C04B 2235/5454 20130101; C04B 2235/72 20130101;
C04B 2235/76 20130101; C01P 2004/03 20130101; H01M 4/485 20130101;
C01P 2004/64 20130101; C01G 23/005 20130101; C04B 2235/5445
20130101; C01P 2006/40 20130101; C04B 35/6263 20130101; C01P
2002/72 20130101; C01P 2006/80 20130101; C04B 35/62615 20130101;
C04B 2235/424 20130101; H01M 4/5825 20130101; C04B 35/6264
20130101 |
Class at
Publication: |
428/402 ; 241/30;
241/22; 241/3; 977/773 |
International
Class: |
B02C 19/00 20060101
B02C019/00; B32B 5/16 20060101 B32B005/16; B02C 19/18 20060101
B02C019/18; B02C 17/00 20060101 B02C017/00 |
Claims
1. A method of producing a lithium-based compound particle
composition, comprising: milling lithium-based compound feed
particles to form a composition including lithium-based compound
milled particles having an average particle size of less than 100
nm and a contamination level of less than 900 ppm.
2. A method as in claim 1, wherein the average particle size is
less than 50 nm.
3. A method as in claim 1, wherein the lithium-based compound feed
particles comprise a lithium phosphate-based compound.
4. A method as in claim 1, wherein the lithium-based compound feed
particles comprise a lithium oxide-based compound.
5. A method as in claim 1, wherein the lithium-based compound feed
particles comprise a lithium titanate-based compound.
6. A method as in claim 1, wherein the grinding media have a
density of greater than 8 gm/cc.
7. A method as in claim 1, wherein the grinding media have a size
between about 120 microns and 150 microns.
8. A milled particle composition, comprising: milled lithium-based
compound particles having an average particle size of less than 100
nm and a contamination level of less than 900 ppm.
9. A method for producing particle compositions, comprising:
heating a lithium-based compound precursor to form a solid body
comprising a lithium-based compound, processing the solid body to
form feed particles comprising the lithium-based compound; and
milling the feed particles to form a composition including
lithium-based compound milled particles having an average particle
size of less than 100 nm.
10. A method for producing particle compositions, comprising:
milling a feed material comprising a lithium-based compound
precursor to form a first milled particle composition including
milled particles, forming aggregates including the milled
particles; processing the aggregates to form a composition
comprising a lithium-based compound; and milling the composition to
form a second milled particle composition including milled
particles having an average particle size of less than 100 nm.
11. A method as in claim 10, wherein the processing comprises
melting the aggregates to form the composition comprising the
lithium-based compound.
12. A method as in claim 10, wherein the processing comprises
reacting the aggregates to form the composition comprising the
lithium-based compound.
Description
RELATED APPLICATIONS
[0001] This applications is a continuation of U.S. patent
application Ser. No. 11/712,831, filed Feb. 28, 2007, which claims
priority to U.S. Provisional Patent Application Ser. No.
60/778,029, filed on Feb. 28, 2007, and U.S. Provisional Patent
Application Ser. No. 60/877,122, filed on Dec. 22, 2006, all of
which are incorporated herein by reference.
FIELD OF INVENTION
[0002] The invention relates to generally to methods of forming
small lithium-based compound particle compositions, as well as
related particle compositions and structures.
BACKGROUND OF THE INVENTION
[0003] Lithium-based compounds, such as lithium metal phosphates
(e.g., LiFePO.sub.4) and lithium metal oxides (e.g.,
LiMnNiO.sub.2), are materials that may be used in electrochemical
cells such as batteries. The materials may be processed, for
example, to form powders that are used to form electrodes (e.g.,
anode, cathode) of the cell. There is a desire in the art to
improve electrochemical performance in cells including increased
charging/discharging rates, increased power density and increased
operational lifetime.
[0004] Milling processes typically use grinding media to crush, or
beat, a product material to smaller dimensions. For example, the
product material may be provided in the form of a powder having
relatively large particles and the milling process may be used to
reduce the size of the particles.
[0005] Grinding media may have a variety of sizes and shapes. In a
typical milling process, the grinding media are used in a device
known as a mill (e.g., ball mill, rod mill, attritor mill, stirred
media mill, pebble mill). Mills typically operate by distributing
product material around the grinding media and rotating to cause
collisions between grinding media that fracture product material
particles into smaller dimensions to produce a milled particle
composition.
SUMMARY OF INVENTION
[0006] Methods of forming small lithium-based compound particle
compositions are provided, as well as related particle compositions
and structures.
[0007] In one aspect, the present invention provides a method for
producing a coated particle composition. The method comprises
providing a feed material comprising feed particles and a coating
material precursor, and a fluid carrier. The method further
comprises milling the feed material to form a composition
comprising milled particles including a coating, wherein the milled
particles have an average particle size of less than 250 nm.
[0008] In another aspect, the present invention provides a method
for producing a lithium-based compound particle composition. The
method comprises milling lithium-based compound feed particles to
form a composition including lithium-based compound milled
particles having an average particle size of less than 100 nm and a
contamination level of less than 900 ppm.
[0009] In another aspect, the present invention provides milled
particle compositions. The milled particle compositions comprise
milled lithium-based compound particles having an average particle
size of less than 100 nm and a contamination level of less than 900
ppm.
[0010] In another aspect, the present invention provides a method
for producing particle compositions. The method comprises heating a
lithium-based compound precursor to form a solid body comprising a
lithium-based compound. The method further comprises processing the
solid body to form feed particles comprising the lithium-based
compound. The method further comprises milling the feed particles
to form a composition including lithium-based compound milled
particles having an average particle size of less than 100 nm.
[0011] In another aspect, the method comprises milling a feed
material comprising a lithium-based compound precursor to form a
first milled particle composition including milled particles. The
method further comprises forming aggregates including the milled
particles and processing the aggregates to form a composition
comprising a lithium-based compound. The method further comprises
milling the composition to form a second milled particle
composition including milled particles having an average particle
size of less than 100 nm.
[0012] Other aspects, embodiments and features of the invention
will become apparent from the following detailed description when
considered in conjunction with the accompanying drawings. The
accompanying figures are schematic and are not intended to be drawn
to scale. For purposes of clarity, not every component is labeled
in every figure. Nor is every component of each embodiment of the
invention shown where illustration is not necessary to allow those
of ordinary skill in the art to understand the invention. All
patent applications and patents incorporated herein by reference
are incorporated by reference in their entirety. In case of
conflict, the present specification, including definitions, will
control.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates a schematic electrochemical cell
including an electrode formed from coated small particle
compositions, according to an embodiment of the present
invention.
[0014] FIG. 2 illustrates a battery structure including an
electrode formed from coated small particle compositions, according
to an embodiment of the present invention.
[0015] FIG. 3 is a copy of a TEM image of LiMnPO.sub.4
nanoparticles described in Example 1.
[0016] FIG. 4 is a plot of XRD data obtained from the LiMnPO.sub.4
particle composition described in Example 1.
[0017] FIGS. 5A-B are copies of SEM images of the LiMnPO.sub.4
particle composition described in Example 3.
[0018] FIGS. 6A-B are copies of SEM images of the carbon-coated
Li.sub.4Ti.sub.5O.sub.12 nanoparticle composition described in
Example 5.
[0019] FIG. 6C is a plot of the XRD data obtained from the
carbon-coated Li.sub.4Ti.sub.5O.sub.12 nanoparticle composition
described in Example 5.
[0020] FIGS. 7A-B are copies of SEM images of the carbon-coated
Li.sub.4Ti.sub.5O.sub.12 described in Example 6.
[0021] FIG. 7C is a plot of the XRD data obtained from the
carbon-coated Li.sub.4Ti.sub.5O.sub.12 nanoparticle composition
described in Example 6.
[0022] FIGS. 8-8A are copies of SEM images of carbon-coated
LiFePO.sub.4 nanoparticle composition described in Example 7.
[0023] FIG. 8B is a plot of the XRD data obtained from the
carbon-coated LiFePO.sub.4 nanoparticle composition described in
Example 7.
DETAILED DESCRIPTION
[0024] Lithium-based compound small particle compositions, as well
as methods and structures associated with the same, are provided.
The particle compositions, in some cases, are characterized by
having a nano-size particles. As described further below, the
particle compositions may be produced in a milling process. The
milling process may use preferred types of grinding media to form
milled particle compositions having the desired characteristics
(e.g., small particle size, shape, low contamination level). In
some embodiments, the particles may be coated with a coating that
may enhance certain properties of the particle composition (e.g.,
electrical conductivity). A coating material precursor can be
milled along with feed material particles under desired conditions
to form the coatings on the particles. The particle compositions
may be used in a variety of different applications including
electrochemical applications, such as in fuel cells,
supercapacitors or as electrodes in batteries.
[0025] As noted above, the particles may comprise a lithium-based
compound. As used herein, a "lithium-based compound" is a compound
that comprises lithium and one or more additional elements.
Examples of suitable lithium-based compounds include lithium
phosphate-based compounds (i.e., compounds that comprise lithium
and a phosphate group (PO.sub.4) and may comprise one or more
additional elements); lithium oxide-based compounds (i.e.,
compounds that comprise lithium and oxygen and may comprise one or
more additional elements); and, lithium titanate-based compounds
(i.e., compounds that comprise lithium and titanium and may
comprise one or more additional elements). For example, suitable
lithium phosphate-based compositions may have the general formula
LiMPO.sub.4, where M may represent one or more metals including
transition metals such as Fe, Mn, Co, Ni, V, Cr, Ti, Mo and Cu.
Examples of suitable lithium phosphate-based compositions include
LiFePO.sub.4, LiMnPO.sub.4 and LiFeMnPO.sub.4. Suitable lithium
oxide-based compositions may have the general formula LiMO.sub.x,
where x is a suitable subscript (e.g., 2) and M may represent one
or more metals including transition metals such as Fe, Mn, Co, Ni,
V, Cr, Ti, Mo and Cu. Examples of suitable lithium oxide-based
compositions include LiMnNiO.sub.2. Suitable lithium titanate-based
compositions include Li.sub.4Ti.sub.5O.sub.12, amongst others. It
should be understood that the particle compositions may also
include suitable dopants which, for example, may enhance electrical
conductivity.
[0026] Suitable lithium-based compounds have been described in U.S.
Pat. Nos. 5,871,866; 6,136,472; 6,153,333; 6,203,946; 6,387,569;
6,387,569; 6,447,951; 6,528,033; 6,645,452; 6,667,599; 6,702,961;
6,716,372; 6,720,110; and, 6,724,173 which are incorporated herein
by reference.
[0027] In some embodiments, the average particle size of the milled
particle composition is less than 500 nm. In certain embodiments,
the average particle size may be even smaller. For example, the
average particle size may be less than 250 nm, less than 150 nm,
less than 100 nm, less than 75 nm, or less than 50 nm. In some
embodiments, it may be preferred for the particle compositions to
have very small particle sizes (e.g., an average particle size of
less than 100 nm). In some cases, it is even possible to produce
particle compositions having an average particle size of less than
30 nm, less than 20 nm, or less than 10 nm. Such particle sizes may
be obtained, in part, by using grinding media having certain
preferred characteristics, as described further below.
[0028] It should be understood that the particle sizes described
herein may be for coated or uncoated lithium-based compound
particle compositions.
[0029] The preferred average particle size of the lithium-based
compound particle compositions typically depends on the intended
application. In certain applications, it may be desired for the
average particle size to be extremely small (e.g., less than 100
nm); while, in other applications, it may be desired for the
average particle size to be slightly larger (e.g., between 100 nm
and 500 nm). In general, milling parameters may be controlled to
provide a desired particle size, though in certain cases it may be
preferable for the average particle size to be greater than 1 nm to
facilitate milling. For example, the average particle size of the
milled material may be controlled by a number of factors including
grinding media characteristics (e.g., density, size, hardness,
toughness), as well as milling conditions (e.g., specific energy
input).
[0030] For purposes of this application, the "average particle
size" of a particle composition is the numeric average of the
"particle size" of a representative number of primary particles
(non-agglomerated) in the composition. The "particle size" of a
primary particle (non-agglomerated) is its maximum cross-sectional
dimension taken along an x, y, or z-axis. For example, the maximum
cross-sectional diameter of a substantially spherical particle is
its diameter. For the values in the description and claims of this
application, the particle sizes are determined using microscopy
techniques, such as scanning electron microscope or transmission
electron microscope techniques.
[0031] It should also be understood that particle compositions
having average particle sizes outside the above-described ranges
(e.g., greater than 500 nm) may be useful in certain embodiments of
the invention.
[0032] The particle compositions may also be relatively free of
large particles. That is, the particle compositions may include
only a small concentration of larger particles. For example, the
D.sub.90 values for the compositions may be any of the
above-described average particle sizes. Though, it should be
understood that the invention is not limited to such D.sub.90
values.
[0033] The particle compositions may also have a very high average
surface area. The high surface area is, in part, due to the very
small particle sizes noted above. The average surface area of the
particle compositions may be greater than 1 m.sup.2/g; in other
cases, greater than 5 m.sup.2/g; and, in other cases, greater than
50 m.sup.2/g. In some cases, the particles may have extremely high
average surface areas of greater than 100 m.sup.2/g; or, even
greater than 500 m.sup.2/g. It should be understood that these high
average surface areas are even achievable in particles that are
non-coated and/or substantially non-porous, though other particles
may have surface pores. Surface area may be measured using
conventional BET measurements. Such high surface areas may be
obtained, in part, by using grinding media having certain preferred
characteristics, as described further below.
[0034] Similar to particle size, the preferred average surface area
of the particle composition typically depends on the intended
application. In certain applications, it may be desired for the
average surface area to be extremely large (e.g., greater than 50
m.sup.2/g, or greater than 260 m.sup.2/g); while, in other
applications, it may be desired for the average surface area to be
slightly smaller (e.g., between 50 m.sup.2/g and 1 m.sup.2/g). In
general, milling parameters may be controlled to provide a desired
surface area, though in certain cases it may be preferable for the
average surface area to be less than 3,000 m.sup.2/g (e.g., for
substantially non-porous particles). For example, the average
surface area of the milled particle compositions may be controlled
by a number of factors including grinding media characteristics
(e.g., density, size, hardness, toughness), as well as milling
conditions (e.g., energy, time).
[0035] Amongst other advantages, the small particle size and/or
high surface areas may lead to improved electrochemical performance
(e.g., for batteries) such as increased charging/discharging rates,
increased capacity, increased power density, increased cost
savings, and increased operational lifetime (e.g., the number of
charging/discharging cycles without degeneration).
[0036] An advantage of certain embodiments of the invention is that
the particle sizes described herein can be achieved at very low
contamination levels. The grinding media noted below may enable the
low contamination levels when used with the above-described
compositions because such characteristics lead to very low wear
rates. For example, the milled compositions may have contamination
levels may be less than 900 ppm, less than 500 ppm, less than 200
ppm, or even less than 100 ppm. In some processes, virtually no
contamination may be detected which is generally representative of
contamination levels of less than 10 ppm. As used herein, a
"contaminant" is grinding media material introduced into the
product material composition during milling. It should be
understood that typical commercially available feed product
materials may include a certain impurity concentration (prior to
milling) and that such impurities are not includes in the
definition of contaminant as used herein. Also, other sources of
impurities introduced in to the product material, such as material
from the milling equipment, are not included in the definition of
contaminant as used herein. The "contamination level" refers to the
weight concentration of the contaminant relative to the weight
concentration of the milled material. Typical units for the
contamination level are ppm. Standard techniques for measuring
contamination levels are known to those of skill in the art
including chemical composition analysis techniques.
[0037] It should be understood that methods of the invention may
produce compositions having any of the particle size values
described herein (including values of relative size between
particles before and after milling) combined with any of the
above-described contamination levels. For example, one method of
the invention involves milling feed particles having an average
initial particle size to form a milled particle composition having
an average final particle size of less than 100 nm, wherein the
initial particle size is greater than 100 times the final particle
size and the milled particle composition has a contamination level
of less than 500 ppm.
[0038] In some processes, the milled particle sizes are achieved
when the feed material particles (prior to milling) have an average
particle size of greater than 1 micron, greater than 10 micron, or
even greater than 50 micron. In some processes, the average
particle size of the feed material particles may be greater than 10
times, 50 times, 100 times, or greater than 500 times the average
particle size of the milled material. The specific particle size of
the milled material depends on a number of factors including
milling conditions (e.g., energy, time), though is also dictated,
in part, by the application in which the milled material is to be
used. In general, the milling conditions may be controlled to
provide a desired final particle size. The particle size of the
feed material may depend on commercial availability, amongst other
factors.
[0039] As noted above, the milled compositions may be produced at
small particle sizes which can lead to a number of performance
advantages. When in bulk composition form, the particles may be
free-standing (i.e., not attached to a surface). As described
further below, such milled particles may be further processed to
form the desired structure (e.g., electrode). In some cases, the
milled particles in the composition may be agglomerated. In some
cases, the milled materials may be provided as a suspension of
milled particles in a fluid carrier. It should be understood that
the average particle sizes and average surface areas described
herein refer to the particle size and surface area of primary
particles (rather than the size and area of agglomerates of primary
particles).
[0040] As described further below, the milled particle compositions
can be produced in a milling process. Thus, these particle
compositions may be described as having a characteristic "milled"
morphology/topology. Those of ordinary skill in the art can
identify "milled particles", which, for example, can include one or
more of the following microscopic features: multiple sharp edges,
faceted surfaces, and being free of smooth rounded "corners" such
as those typically observed in chemically-precipitated particles.
It should be understood that the milled particles described herein
may have one or more of the above-described microscopic features,
while having other shapes (e.g., platelet) when viewed at lower
magnifications.
[0041] It should be understood that not all embodiments of the
invention are limited to milled particles or milling processes.
[0042] In some embodiments, it may be preferable for the particles
to have a platelet shape. In these cases, the particles may have a
relatively uniform thickness across the length of the particle. The
particles may have a substantially planar first surface and a
substantially planar second surface with the thickness extending
therebetween. The particle thickness may be smaller than the
particle width and particle length. In some embodiments, the length
and width may be approximately equal; however, in other embodiments
the length and width may be different. In cases where the length
and width are different, the platelet particles may have a
rectangular box shape. In certain cases, the particles may be
characterized as having sharp edges. For example, the angle between
a top surface (e.g., first planar surface) of the particle and a
side surface of the particle may be between 75.degree. and
105.degree.; or between 85.degree. and 95.degree. degrees (e.g.,
about 90.degree.). However, it should be understood that the
particles may not have platelet shapes in all embodiments and that
the invention is not limited in this regard. For example, the
particles may have a substantially spherical or oblate spheroid
shape, amongst others. It should be understood that within a milled
particle composition, individual particles may be in the form of
one or more of the above-described shapes.
[0043] In some cases, the shape of the particle may be altered upon
coating.
[0044] In some embodiments, the compositions of the invention may
comprise particles having a preferred crystallographic orientation.
Suitable methods of forming the such particles have been described
in commonly-owned, co-pending U.S. patent application Ser. No.
11/318,314, entitled "Small Particle Compositions and Associated
Methods", filed on Oct. 27, 2005, which is incorporated herein by
reference. In some embodiments, a majority (i.e., greater than 50%)
of the particles in a composition may have the same
crystallographic orientation. In other embodiments, greater than
75% of the particles, or even greater than 95%, or even
substantially all, of the particles in a composition may have the
same crystallographic orientation.
[0045] The preferred crystallographic orientation of the particles
may depend, in part, on the crystal structure (e.g., olivine,
spinel, hexagonal, tetragonal, cubic) of the material that forms
the particles. Crystals generally preferentially fracture along
specific planes with characteristic amounts of energy being
required to induce fracture along such planes. During milling, such
energy results from particle/grinding media collisions. It is
observed that, by controlling the energy of such collisions via
milling parameters (e.g., grinding media composition, specific
energy input), it is possible to preferentially fracture particles
along certain crystallographic planes which creates a particle
composition having a preferred crystallographic orientation.
[0046] In some embodiments, the preferred crystallographic
orientation is defined by a basal plane (i.e., the plane which is
perpendicular to the principal axis (c axis) in a tetragonal or
hexagonal structure). For example, the basal plane, and
crystallographic orientation, may be the (0001) or (001) plane.
[0047] Crystallographic orientation of particles may be measured
using known techniques. A suitable technique is x-ray diffraction
(XRD). It may be possible to assess the relative percentage of
particles having the same preferred crystallographic orientation
using XRD.
[0048] As noted above, in some embodiments, the particles may be
coated. The coating covers at least a portion of the surface area
of the particles. In some cases, the coating may cover greater than
50%, greater than 75%, or substantially the entire (e.g., greater
than 99%) surface area of the particles. The coating may have a
thickness of less than 50 nm, less than 25 nm, or, in some cases,
less than 10 nm. In some embodiments, the coating may have uniform
thickness over a majority of the surface area of the particles. For
example, the coating may have a thickness that varies less than 20%
on greater than 50% of the surface area of the particles.
[0049] The coating may be used to enhance one or more properties of
the particle compositions. For example, the coating may improve the
performance of the particles in an electrode (e.g., of an
electrochemical cell), wherein the coated particles may exhibit
improved conductivity when compared to uncoated particles. In some
cases, the coated particles may facilitate the transport of lithium
or lithium ions within the electrochemical cell. Also, particles
having a uniform coating may exhibit more consistent properties
than particles having a non-uniform coating.
[0050] The coating material, and the coating material precursor,
may be any suitable material capable of coating the surface of a
particle. In some cases, the coating material is an electrically
conductive material. In some embodiments, the coating may be
comprised substantially of carbon. For example, the coating
material precursor may be provided by a carbon-containing material
such as graphite (e.g., superior graphite), carbon nanotubes,
acetylene black, polyols, or the like, and may be used to coat
particles in processes as described herein. In some embodiments,
the coating may comprise an inorganic material, such as metal
oxides or metal nitrides. Some specific examples of inorganic
materials include alumina and ceria. In some embodiments, the
coating may comprise a metal, such as Cu or Sn. The coating
material may further comprise additional components to enhance the
surface of the particles, such as silanes, for example. It should
be understood that other coating compositions are also
possible.
[0051] The coating material precursor may be in the form of
particles (e.g., nanoparticles) that are smaller in size than the
lithium-based compound particles. The coating material precursor
particles may be attached to surfaces of the lithium-based compound
particles to form a coating. The coating (e.g., coating material
particles) may be attached to the lithium-based compound particles
via covalent or non-covalent interactions (e.g., hydrogen-bonding,
ionic bonding, electrostatic interactions, van der Waals
interactions, etc.).
[0052] Compositions containing particles (e.g., active material)
dispersed within a support material, such as a carbon support
material, may also be formed. Such compositions may have particles
that are separated from one another, which may increase the exposed
surface area of the particles.
[0053] As noted above, lithium-based compound particle compositions
may be used in a number of applications including electrochemical
applications. FIG. 1 schematically illustrates an electrochemical
cell 10 according to one embodiment of the invention. The
electrochemical cell includes an anode 12 (i.e., negative
electrode) connected to a cathode 14 (i.e., positive electrode) via
an external circuit 16. The anode and/or cathode may comprise the
lithium-based compound particle compositions described herein. An
oxidation reaction occurs at the anode where electrons are lost and
a reduction reaction occurs at the cathode where electrons are
gained. An electrolyte 18 allows positive ions to flow from the
anode to the cathode, while electrons flow through the external
circuit which can function as a power source. A separator may
electrically isolate the anode and the cathode, amongst other
functions.
[0054] FIG. 2 schematically illustrates a battery cell structure 20
according to another embodiment of the invention. The battery cell
structure includes an anode side 22, a cathode side 24 and an
electrolyte/separator 26 positioned therebetween. The anode side
includes a current collector 28 (e.g. formed of copper open mesh
grid) formed on an active material layer 30. The cathode side
includes a current collector 32 (e.g., formed of an aluminum open
mesh grid) and an active material layer 34. A protective cover 38
may surround the battery cell structure.
[0055] Any suitable electrolyte/separator may be used. For example,
the electrolyte/separator may be a solid electrolyte or separator
and liquid electrolyte. Solid electrolytes can include polymer
matrixes. Liquid electrolytes can comprise a solvent and an
alkaline metal salt, which form an ionically conducting liquid.
[0056] The lithium-based compound particle compositions may be
dispersed in a matrix of other components including binder
materials to form anode and cathode active material layers 30,
34.
[0057] It should be understood that electrochemical cells (e.g.,
batteries) of the invention may have a variety of different
structures constructions and the invention is not limited in this
regard. Suitable electrochemical cells (e.g., batteries) have been
described in some of the U.S. patents incorporated herein by
reference above.
[0058] Particle compositions may be produced in a milling process
that use grinding media as described herein. The processes may
utilize a wide range of conventional mills having a variety of
different designs and capacities. Suitable types of mills include,
but are not limited to, ball mills, rod mills, attritor mills,
stirred media mills, pebble mills and vibratory mills, among
others. In some cases, the milling process may be used to
de-agglomerate particles in the fluid carrier. In some cases, the
milling process may also be used to produce coated particles as
described herein.
[0059] In some cases, conventional milling conditions (e.g.,
energy, time) may be used to process the particle compositions
using the grinding media described herein. In other cases, the
grinding media described herein may enable use of milling
conditions that are significantly less burdensome (e.g., less
energy, less time) than those of typical conventional milling
processes, while achieving a superior milling performance (e.g.,
very small average particle sizes). In some cases, the stress
energy may be greater than that of typical conventional milling
processes.
[0060] Advantageously, the grinding media enable advantageous
milling conditions. For example, lower milling times and specific
energy inputs can be utilized because of the high milling
efficiency of the grinding media of the invention. As used herein,
the "specific energy input" is the milling energy consumed per
weight product material. Even milled particle compositions having
the above-noted particle sizes and contamination levels can be
produced at low milling input energies and/or low milling times.
For example, the specific energy input may be less than 125,000
kJ/kg; or less than 90,000 kJ/kg. In some cases, the specific
energy input may be even lower such as less than 50,000 kJ/kg or
less than 25,000 kJ/kg. The actual specific energy input and
milling time depends strongly on the composition of the product
material and the desired reduction in particle size, amongst other
factors.
[0061] Milling processes of the invention can involve the
introduction of feed product material (e.g., feed particles) and a
fluid carrier into a processing space in a mill in which the
grinding media are confined. The viscosity of the slurry may be
controlled, for example, by adding additives to the slurry such as
dispersants. The mill is rotated at a desired speed and material
particles mix with the grinding media. Collisions between the
particles and the grinding media can reduce the size of the
particles. The particles are typically exposed to the grinding
media for a certain mill time after which the milled material is
separated from the grinding media using conventional techniques,
such as washing and filtering, screening or gravitation separation.
The milling process may be performed at any temperature, including
room temperature. In some processes, the slurry of particles is
introduced through a mill inlet and, after milling, recovered from
a mill outlet. The process may be repeated and, a number of mills
may be used sequentially with the outlet of one mill being fluidly
connected to the inlet of the subsequent mill.
[0062] The milling process may be performed under ambient
conditions (e.g., under exposure to air). The milling process may
also be performed in the absence of air, for example, under a
nitrogen atmosphere, argon atmosphere, or other suitable
conditions.
[0063] As noted above, it may be preferred to use grinding media
having specific characteristics. However, it should be understood
that not every embodiment of the invention is limited in this
regard. In some embodiments, the grinding media is formed of a
material having a density of greater than 6 grams/cm.sup.3; in some
embodiments, greater than 8 grams/cm.sup.3; in some embodiments,
the density is greater than 10 grams/cm.sup.3; or greater than 15
grams/cm.sup.3; or, even, greater than 18 grams/cm.sup.3. Though,
in certain embodiments, the density of the grinding media may be
less than 22 grams/cm.sup.3, in part, due to difficulties in
producing suitable grinding materials having greater densities. It
should be understood that conventional techniques may be used to
measure grinding media material density.
[0064] In certain embodiments, it also may be preferable for the
grinding media to be formed of a material having a high fracture
toughness. For example, in some cases, the grinding media is formed
of a material having a fracture toughness of greater than 6
MPa/m.sup.1/2; and in some cases, the fracture toughness is greater
than 9 MPa/m.sup.1/2. The fracture toughness may be greater than 12
MPa/m.sup.1/2 in certain embodiments. Conventional techniques may
be used to measure fracture toughness. Suitable techniques may
depend, in part, on the type of material being tested and are known
to those of ordinary skill in the art. For example, an indentation
fracture toughness test may be used. Also, a Palmqvist fracture
toughness technique may be suitable, for example, when testing hard
metals.
[0065] It should be understood that the fracture toughness values
disclosed herein refer to fracture toughness values measured on
bulk samples of the material. In some cases, for example, when the
grinding media are in the form of very small particles (e.g., less
than 150 micron), it may be difficult to measure fracture toughness
and the actual fracture toughness may be different than that
measured on the bulk samples.
[0066] In certain embodiments, it also may be preferable for the
grinding media to be formed of a material having a high hardness.
It has been found that media having a high hardness can lead to
increased energy transfer per collision with product material
which, in turn, can increase milling efficiency. In some
embodiments, the grinding media is formed a material having a
hardness of greater than 75 kgf/mm.sup.2; and, in some cases, the
hardness is greater than 200 kgf/mm.sup.2. The hardness may even be
greater than 900 kgf/mm.sup.2 in certain embodiments. Conventional
techniques may be used to measure hardness. Suitable techniques
depend, in part, on the type of material being tested and are known
to those of ordinary skill in the art. For example, suitable
techniques may include Rockwell hardness tests or Vickers hardness
tests (following ASTM 1327). It should be understood that the
hardness values disclosed herein refer to hardness values measured
on bulk samples of the material. In some cases, for example, when
the grinding media are in the form of very small particles (e.g.,
less than 150 micron), it may be difficult to measure hardness and
the actual hardness may be greater than that measured on the bulk
samples.
[0067] It should be understood that not all milling processes of
the present invention use grinding media having each of the
above-described characteristics.
[0068] Milling processes of the invention may use grinding media
having a wide range of dimensions. In general, the average size of
the grinding media is between about 0.5 micron and 10 cm. The
preferred size of the grinding media used depends of a number of
factors including the size of the feed particles, desired size of
the milled particle composition, grinding media composition, and
grinding media density, amongst others.
[0069] In certain embodiments, it may be advantageous to use
grinding media that are very small. It may be preferred to use
grinding media having an average size of less than about 250
microns; or, less than about 150 microns (e.g., between about 75
and 150 microns). In some cases, the grinding media may have an
average size of less than about 100 microns; or even less than
about 10 microns. Grinding media having a small size have been
shown to be particularly effective in producing particle
compositions having very small particle sizes (e.g., less than 1
micron). In some cases, the grinding media may have an average size
of greater than 0.5 micron.
[0070] It should be understood that the average size of grinding
media used in a process may be determined by measuring the
cross-sectional dimension (e.g., diameter for substantially
spherical grinding media) of a representative number of grinding
media particles.
[0071] The grinding media may also have a variety of shapes. In
general, the grinding media may have any suitable shape known in
the art. In some embodiments, it is preferred that the grinding
media be substantially spherical (which may be used herein
interchangeably with "spherical"). Substantially spherical grinding
media have been found to be particularly effective in obtaining
desired milling performance.
[0072] It should also be understood that any of the grinding media
used in methods of the invention may have any of the
characteristics (e.g., properties, size, shape, composition)
described herein in combination with one another. For example,
grinding media used in methods of the invention may have any of the
above-noted densities and above-noted average sizes (e.g., grinding
media may have a density of greater than about 6 grams/cm.sup.3 and
an average size of less than about 250 micron).
[0073] The above-described grinding media characteristics (e.g.,
density, hardness, toughness) are dictated, in part, by the
composition of the grinding media. In certain embodiments, the
grinding media may be formed of a metallic material including metal
alloys or metal compounds. In one set of embodiments, it may be
preferred that the grinding media are formed of ferro-tungsten
material (i.e., Fe--W). In some cases, the compositions may
comprise between 75 and 80 weight percent iron and between 20 and
25 weight percent tungsten. In some cases, ferro-tungsten grinding
media may be carburized to improve wear resistance.
[0074] In other embodiments, the grinding media may be formed of a
ceramic material such as a carbide material. In some embodiments,
the grinding media to be formed of a single carbide material (e.g.,
iron carbide (Fe.sub.3C), chromium carbide (Cr.sub.7C.sub.3),
molybdenum carbide (Mo.sub.2C), tungsten carbide (WC, W.sub.2C),
niobium carbide (NbC), vanadium carbide (VC), and titanium carbide
(TiC)). In some cases, it may be preferred for the grinding media
to be formed of a multi-carbide material. A multi-carbide material
comprises at least two carbide forming elements (e.g., metal
elements) and carbon.
[0075] A multi-carbide material may comprise a multi-carbide
compound (i.e., a carbide compound having a specific stoichiometry;
or, a blend of single carbide compounds (e.g., blend of WC and
TiC); or, both a multi-carbide compound and a blend of single
carbide compounds. It should be understood that multi-carbide
materials may also include other components such as nitrogen,
carbide-forming elements that are in elemental form (e.g., that
were not converted to a carbide during processing of the
multi-carbide material), amongst others including those present as
impurities. Typically, but not always, these other components are
present in relatively minor amounts (e.g., less than 10 atomic
percent).
[0076] Suitable carbide-forming elements in multi-carbide grinding
media of the invention include iron, chromium, hafnium, molybdenum,
niobium, rhenium, tantalum, titanium, tungsten, vanadium,
zirconium, though other elements may also be suitable. In some
cases, the multi-carbide material comprises at least two of these
elements. For example, in some embodiments, the multi-carbide
material comprises tungsten, rhenium and carbon; in other cases,
tungsten, hafnium and carbon; in other cases, molybdenum, titanium
and carbon.
[0077] Suitable grinding media compositions have been described,
for example, in U.S. Patent Application Publication No.
2006-0003013 which is incorporated herein by reference and is based
on U.S. patent application Ser. No. 11/193,688, filed on Jul. 29,
2005, entitled "Grinding Media Compositions and Methods Associated
With the Same". Suitable grinding media compositions have also been
described, for example, U.S. Pat. No. 7,140,567 which is
incorporated herein by reference.
[0078] In some embodiments, it may be preferred for the
multi-carbide material to comprise at least tungsten, titanium and
carbon. In some of these cases, the multi-carbide material may
consist essentially of tungsten, titanium and carbon, and is free
of additional elements in amounts that materially affect
properties. Though in other cases, the multi-carbide material may
include additional metal carbide forming elements in amounts that
materially affect properties. For example, in these embodiments,
tungsten may be present in the multi-carbide material in amounts
between 10 and 90 atomic %; and, in some embodiments, in amounts
between 30 and 50 atomic %. The amount of titanium in the
multi-carbide material may be between 1 and 97 atomic %; and, in
some embodiments, between 2 and 50 atomic %. In these embodiments
that utilize tungsten-titanium carbide multi-carbide material, the
balance may be carbon. For example, carbon may be present in
amounts between 10 and 40 atomic %. As noted above, it should also
be understood that any other suitable carbide forming elements can
also be present in the multi-carbide material in these embodiments
in addition to tungsten, titanium and carbon. In some cases, one or
more suitable carbide forming elements may substitute for titanium
at certain sites in the multi-carbide crystal structure. Hafnium,
niobium, tantalum and zirconium may be particularly preferred as
elements that can substitute for titanium. Carbide-forming elements
that substitute for titanium may be present, for example, in
amounts of up to 30 atomic % (based on the multi-carbide material).
In some cases, suitable multi-carbide elements may substitute for
tungsten at certain sites in the multi-carbide crystal structure.
Chromium, molybdenum, vanadium, tantalum, and niobium may be
particularly preferred as elements that can substitute for
tungsten. Carbide-forming elements that substitute for tungsten may
be present, for example, in amounts of up to 30 atomic % (based on
the multi-carbide material).
[0079] It should also be understood that the substituting carbide
forming elements noted above may completely substitute for titanium
and/or tungsten to form a multi-carbide material free of tungsten
and/or titanium.
[0080] It should be understood that grinding media compositions
that are not disclosed herein but have certain above-noted
characteristics (e.g., high density) may be used in embodiments of
the invention. Also, it should be understood that milling processes
of the present invention are not limited to the grinding media
compositions and/or characteristics described herein. Other
suitable grinding media may also be used.
[0081] In general, any suitable process for forming grinding media
compositions may be used. In some cases, the processes involve
heating the components of the composition to temperatures higher
than the respective melting temperatures of the components followed
by a cooling step to form the grinding media. A variety of
different heating techniques may be used including a thermal plasma
torch, melt atomization, and arc melting, amongst others. For
example, one suitable process involves admixing fine particles of
the elements intended to comprise the grinding media in appropriate
ratios. The stability of the mixture may be enhanced by
introduction of an inert binding agent (e.g., which burns off and
does not form a component of the grinding material). The mixture
may be subdivided into a plurality of aggregates (e.g., each having
a mass approximately equal to that of the desired media particle to
be formed). The aggregates may be heated to fuse (e.g., to 90% of
theoretical density) and, eventually, melt individual aggregates to
form droplets that are cooled to form the grinding media.
[0082] In some embodiments, the grinding media may be formed of two
different materials. For example, the grinding media may be formed
of a blend of two different ceramic materials (e.g., a blend of
high density ceramic particles in a ceramic matrix); or a blend of
a ceramic material and a metal (e.g., a blend of high density
ceramic materials in a metal matrix).
[0083] In some embodiments in which the grinding media comprises
more than one material component, the grinding media may comprise
coated particles. The particles may have a core material and a
coating formed on the core material. The coating typically
completely covers the core material, but not in all cases. The
composition of the core and coating materials may be selected to
provide the grinding media with desired properties such as a high
density. For example, the core material may be formed of a high
density material (e.g., greater than 8 grams/cm.sup.3). The core,
for example, may be formed of a metal such as steel or depleted
uranium; or a ceramic such as a metal carbide.
[0084] As noted above, the lithium-based compound particles may be
coated. A milling process may be used to produce coated particles.
It may be preferred for the same milling process used to reduce the
size of the lithium-based compound particles also to be used to
coat the particles. In these embodiments, particle size reduction
is done in-situ with coating. In some cases, the size reduction and
coating steps can occur consecutively; in other cases, size
reduction and coating may occur at least somewhat (or entirely)
simultaneously. In some embodiments, the milling process may also
be used to de-agglomerate the lithium-based compound particles
and/or the coating material precursor particles (when present). In
these embodiments, de-agglomeration can be done in-situ with
particle size reduction and coating.
[0085] In some embodiments, a lithium-based compound feed material
including feed particles and a coating material precursor (e.g.,
coating material precursor particles) is suspended in a fluid
carrier, and the suspension may be milled. As noted above, any
suitable coating material precursor particle composition may be
used, such as carbon black particles. In some cases, the fluid
carrier is aqueous (e.g., water, or water-soluble fluids). In some
cases, the fluid carrier is non-aqueous (e.g., an organic solvent).
The feed material may be combined with a fluid carrier prior to
and/or during milling. In some embodiments, the feed particles and
coating material precursor may be milled in the absence of the
fluid carrier to partially coat the particles, which may then be
combined with the fluid carrier and milled.
[0086] The fluid carrier may be selected such that, when milling
occurs under ambient conditions (e.g., exposure to air), the fluid
carrier does not undergo a chemical reaction with the feed
material. For example, in the presence of oxygen, a feed material
might participate in a chemical reaction with fluid carriers such
as water, such that the feed material is altered. In some cases, a
feed material including a metal oxide (e.g., iron oxide or
manganese oxide) may be oxidized in the presence of water and air.
Methods of the invention may advantageously reduce or prevent such
reactions by selecting solvents (e.g., NMP, isopropyl alcohol)
which are essentially inert to the feed material, upon exposure to
ambient conditions.
[0087] In some cases, the entire milling and coating process is
performed in the absence of a fluid carrier (i.e., a dry
process).
[0088] In some embodiments, a suspension containing the
lithium-based compound feed particles and the fluid carrier may be
milled to de-agglomerate the feed particles within the fluid
carrier prior to adding the coating material precursor particles.
Also, the coating material precursor particles may be
de-agglomerated by milling prior to attaching to surfaces of the
lithium-based compound particles.
[0089] In certain embodiments, the milling process may also be used
to produce a composition containing particles dispersed within a
support material. For example, a feed material including feed
particles and a support material precursor (e.g., carbon) may be
milled as described herein.
[0090] The suspension comprising the feed material and the fluid
carrier may comprise at least 10% solid loading (e.g., feed
particles and coating material precursor) of the feed material in
the fluid carrier. In some cases, the suspension comprises at least
20%, at least 30% at least 40%, or, in some case, at least 50%
solid loading of the feed material in the fluid carrier. In one set
of embodiments, the suspension comprises 20-25% solid loading of
the feed material in the fluid carrier. In some cases, the
suspension comprises 10-20 wt % solid loading of the feed material
in the fluid carrier.
[0091] It should be understood that the feed material may comprise
additional components, such as surfactants, binders, acids, bases,
or other suitable dopants which may enhance the ability of the feed
material to form coated, milled particles using methods of the
invention.
[0092] The lithium-based compound feed particles and the coating
material precursor may interact to form a coated particle. In some
cases, the interaction may be a mechanical interaction. In some
cases, the interaction may be an electrostatic interaction. For
example, the lithium-based compound particle may have a relatively
negatively charged surface and the coating material precursor
particles may have a relatively positively charged surface, such
that, upon milling, the lithium-based compound particles are coated
with the coating material precursor particles via an electrostatic
interaction to produce milled, coated particles. Various components
of the lithium-based compound particles may be treated to have a
charged surface, either prior to or during milling. In some cases,
a component of the lithium-based compound may be treated with a
chemical reagent such as an acid.
[0093] The fluid carrier may also be capable of facilitating the
coating and/or milling process by enhancing a property, such as an
electrostatic property, of the particle or the coating material
precursor. For example, the feed particles may comprise a material
that, when combined with a fluid carrier, may interact with the
fluid carrier produce a charged surface.
[0094] In an illustrative embodiment, a feed material comprising
feed particles and a coating material precursor may be combined
with an aqueous fluid carrier such as water or
N-methyl-pyrrolidinone (NMP). The feed particles may comprise a
lithium-based compound (e.g., a lithium phosphate-based compound),
such that, when the feed particles are combined with the aqueous
fluid carrier, the feed particles have a negatively charged
surface. The coating material precursor may be treated with an acid
such that the coating material precursor has a positively charged
surface. Combination of the negatively charged feed particles and
the positively charged coating material precursor in a milling
process as described herein may then produce coated, milled
lithium-based compound particles.
[0095] In some cases, electrode materials may be produced using
methods involving a fluid carrier, such as NMP, as described
herein.
[0096] Fluid carriers suitable for use in the invention may include
any fluid capable of forming a fluid mixture, solution, suspension,
or dispersion with components of the feed material (e.g., feed
particle, coating material precursor). The fluid carrier may be
aqueous or non-aqueous (e.g., organic). In some cases, the fluid
carrier is hydrophobic. In some cases, the fluid carrier is
hydrophilic. Examples of fluid carriers may include neat water,
aqueous solutions, hydrocarbons such as hexanes, aromatic
hydrocarbons, ethers, and the like. In some cases, the solvent may
be N-methylpyrrolidinone (NMP), N,N-dimethylformamide (DMF),
dimethylsulfoxide (DMSO), and the like.
[0097] The lithium-based compound feed particles may be evenly
dispersed within the fluid carrier, such that aggregation of
particles may be reduced. This may facilitate uniform coating of
the particles, allowing a substantial majority of individual
particles to contact the coating material precursor. In contrast,
particles which form an agglomeration of particles may not be
uniformly coated, as the coating material precursor may only
contact particles on the exterior of the agglomeration.
[0098] Another aspect of the invention is that the small particle
compositions of the invention may be produced using very low
specific energy input (i.e., energy consumed in milling process per
weight of feed material).
[0099] In another embodiment, the milling process may involve
milling a feed material comprising feed particles and a support
material precursor to form a composition comprising milled
particles supported by the support material. In this embodiment,
the milled particles are substantially separated from one another
within the support material.
[0100] Some embodiments of the invention may involve melt
processing steps that can be used in combination with the milling
processes above to produce lithium-based compound nanoparticle
compositions. The melt process may be used in the formation of a
solid body and/or may involve a chemical reaction. In some cases,
the chemical reaction may involve heating lithium-based compound
precursors (such as lithium carbonate and iron phosphate), with or
without additional components, to produce a lithium-based compound.
The lithium-based compound precursors may be in the form of
nanoparticles. In some cases, a solid state reaction (e.g., a melt
process) between lithium-based compound precursors (e.g., lithium
carbonate and iron phosphate) may produce a lithium-based compound
(e.g., lithium iron phosphate). In some embodiments, the method may
involve heating (e.g., melting) lithium-based compound precursors
to form a solid body comprising the lithium-based compound. The
solid body may then be processed using known methods to produce
lithium-based compound feed particles. For example, the solid body
may be crushed to produce feed particles. The feed particles may
then be milled as described herein to produce the lithium-based
compound nanoparticle compositions.
[0101] In some embodiments, the methods may involve milling a feed
material including lithium-based compound precursor(s) to form a
milled particle composition. The milled particle composition may
include milled particles comprising the lithium-based compound
precursor(s). The milled particle composition may be treated to
form aggregates, which can be further processed to form a
composition comprising a lithium-based compound. For example, the
aggregate may be melted or otherwise reacted such that a chemical
reaction occurs to form a composition comprising a lithium-based
compound. In some cases, the aggregate may be treated in a furnace,
where individual aggregates are dropped and melted in flight. The
composition may then be milled as described herein to produce the
lithium-based compound nanoparticle compositions. In some cases,
the aggregates may be reacted such that the components of the
milled particles react to produce particles containing the
lithium-based compound, which may be further milled as described
herein to produce the lithium-based compound nanoparticle
compositions.
[0102] Methods involving a melt process may also be used to produce
coated milled particle compositions. The coating precursor
(including those described above) may be introduced at any time,
such as during the milling, heating/melting, reacting, or any other
processing step, to form coated milled particle compositions.
[0103] The particles may be further processed as desired for the
intended application. For example, known processing techniques may
be used to incorporate the particles in components (e.g.,
electrodes) used in electrochemical cells (e.g., batteries) as
described above. The electrochemical cells (e.g., batteries) may be
used in applications requiring small dimensions such as smart
cards. In some embodiments, the particles may be coated with a thin
layer of material (e.g., carbon). It should be understood that
particles that the lithium phosphate-based compositions may be used
in any other suitable application and that the invention is not
limited in this regard.
[0104] Particles which are processed using methods described herein
may have many advantages. For example, the particles may be more
uniformly coated than particles coated using known methods. This
may produce particles having improved (e.g., more consistent)
properties. Milling processes of the invention may be simple and
efficient and may eliminate the need for additional processing
steps, when compared to known methods. In some cases, the feed
particles may be milled and coated in one milling step. In some
cases, the desired particle composition (including desired particle
sizes) may be obtained without need for additional processing
steps, such as spray-drying, re-firing, etc. For example, in one
embodiment, the milled particle composition may include
crystalline, milled particles, without requiring an additional step
to provide a crystalline structure. In some cases, the milling
process retains the crystalline structure of the feed particles
(prior to milling) in the milled particles. For example, the feed
particles and the milled particles may both have a spinel
structure; or, the feed particles and the milled particles may both
have an olivine structure. Methods of the invention may provide
more simple, cost-effective methods for processing particles
including coated particles.
[0105] The following examples should not be considered to be
limiting but illustrative of certain features of the invention.
EXAMPLE 1
[0106] This example illustrates production of a lithium-based
compound particle composition in accordance with an embodiment of
the present invention.
[0107] LiMnPO.sub.4 nanoparticle compositions were produced in a
milling process. The milling process used a mill and multi-carbide
material grinding media having a relatively high mass density and a
size of between about 75 and 125 microns. About 20 grams of
LiMnPO.sub.4 was dispersed in water to form a solids loading of
about 9% by weight. The specific energy applied to the slurry was
79,600 kJ/kg. Milled particles were produced and collected.
[0108] The milled particles were characterized using several
techniques. The BET surface area was measured to be about 37
m.sup.2/g using a multi-point BET measurement instrument. Particle
size analysis was conducted using a TEM. The average particle size
was determined to be less than 50 nm. FIG. 3 is a copy of a TEM
image showing a representative portion of the milled nanoparticle
composition. XRD analysis indicated that the LiMnPO.sub.4 had a
pure olivine crystal structure which is identical to the crystal
structure of the feed particles (prior to milling). FIG. 4 is a
plot of the XRD data.
EXAMPLE 2
[0109] This example illustrates production of a lithium-based
compound coated particle composition in accordance with an
embodiment of the present invention.
[0110] Carbon-coated LiMnPO.sub.4 nanoparticle compositions were
produced in a milling process. The milling process used a mill and
multi-carbide material grinding media. About 20 g LiMnPO.sub.4 was
added slowly to 265 g of H.sub.2O within the mill and processed at
a specific energy of 5000 kJ/kg to de-agglomerate the particles to
form a slurry. Conductive carbon black particles (3.5 g) was added
directly to the slurry within the mill and was processed at a
specific energy of 20,000 kJ/kg. Nitric acid was added to the
slurry within the mill to promote deposition of the carbon black
particles on surfaces of the LiMnPO.sub.4 particles thereby forming
coatings. The resulting material was dried under vacuum at a
minimum heat setting until dry (about 96 hours) and carbon-coated
LiMnPO.sub.4 nanoparticle compositions were obtained.
EXAMPLE 3
[0111] This example illustrates production of a lithium-based
compound coated particle composition in accordance with an
embodiment of the present invention.
[0112] Carbon-coated LiMnPO.sub.4 nanoparticle compositions were
produced in a milling process. The milling process used a mill and
Zirmil.RTM. grinding media (commercially available from
Saint-Gobain). About 15 g LiMnPO.sub.4 was mixed with 200 g of
H.sub.2O within the mill to form a slurry. Conductive carbon black
particles (2.6 g), 10 mL of water, and a drop of nitric acid were
added directly to the slurry within the mill and the slurry was
processed at a specific energy of 26,400 kJ/kg. The nitric acid was
added to the slurry within the mill to promote deposition of the
carbon black particles on surfaces of the LiMnPO.sub.4 particles
thereby forming coatings. A peristaltic pump was used with an
agitator speed of 1269 rpm. Carbon-coated LiMnPO.sub.4 nanoparticle
compositions were obtained.
[0113] Particle size analysis was conducted using an SEM. The
average particle size was determined to be less than 200 nm. FIGS.
5A-B are copies of SEM images showing a representative portion of
the milled nanoparticle composition.
EXAMPLE 4
[0114] This example illustrates production of a lithium-based
compound coated particle composition in accordance with an
embodiment of the present invention.
[0115] Carbon-coated LiMnPO.sub.4 nanoparticle compositions were
produced in a milling process. The milling process used a mill and
Zirmil.RTM. grinding media (commercially available from
Saint-Gobain). About 20 g LiMnPO.sub.4 was mixed with 170 g of NMP
within the mill to form a slurry. Conductive carbon black particles
(3.5 g) were added directly to the slurry within the mill and the
slurry was processed at a specific energy of 10,500 kJ/kg. A
peristaltic pump was used with an agitator speed of 1746 rpm.
Carbon-coated LiMnPO.sub.4 nanoparticle compositions were
obtained.
EXAMPLE 5
[0116] This example illustrates production of a lithium-based
compound coated particle composition in accordance with an
embodiment of the present invention.
[0117] Carbon-coated Li.sub.4Ti.sub.5O.sub.12 nanoparticle
compositions were produced in a milling process. The milling
process used a mill and multi-carbide material grinding media.
About 30 g Li.sub.4Ti.sub.5O.sub.12 was mixed with 200 g of
H.sub.2O and one drop of Sokolan PA80S within the mill to form a
slurry. The pH of the mixture was adjusted to 12 by adding two
drops of a 6M KOH solution. The slurry was processed at a specific
energy of 50,000 kJ/kg. A peristaltic pump was used with an
agitator speed of 1212 rpm. Carbon-coated Li.sub.4Ti.sub.5O.sub.12
nanoparticle compositions were obtained.
[0118] The milled particles were characterized using several
techniques. The BET surface area was measured to be about 115
m.sup.2/g using a multi-point BET measurement instrument. Particle
size analysis was conducted using an SEM. The average particle size
was determined to be between about 30 and 50 nm, with the particles
having a substantially spherical morphology. FIGS. 6A-B are copies
of SEM images showing a representative portion of the milled
nanoparticle composition. XRD analysis indicated that the
carbon-coated Li.sub.4Ti.sub.5O.sub.12 nanoparticle composition had
a crystal structure which is identical to the crystal structure of
the feed particles (prior to milling). FIG. 6C is a plot of the XRD
data.
EXAMPLE 6
[0119] This example illustrates production of a lithium-based
compound coated particle composition in accordance with an
embodiment of the present invention.
[0120] Carbon-coated Li.sub.4Ti.sub.5O.sub.12 nanoparticle
compositions were produced in a milling process. The milling
process used a mill and multi-carbide material grinding media
grinding media. About 30 g Li.sub.4Ti.sub.5O.sub.12 was mixed with
200 g of isopropyl alcohol (IPA) and 0.2% 3,6,9-trioxadecanoic acid
within the mill to form a slurry. The slurry was processed at a
specific energy of 50,000 kJ/kg. A peristaltic pump was used with
an agitator speed of 1212 rpm. Carbon-coated
Li.sub.4Ti.sub.5O.sub.12 nanoparticle compositions were
obtained.
[0121] The milled particles were characterized using several
techniques. Particle size analysis was conducted using an SEM. The
average particle size was determined to be between about 30 and 50
nm, with the particles having a platelet morphology. FIGS. 7A-B are
copies of SEM images showing a representative portion of the milled
nanoparticle composition. XRD analysis indicated that the
carbon-coated Li.sub.4Ti.sub.5O.sub.12 nanoparticle composition had
crystal structure which is identical to the crystal structure of
the feed particles (prior to milling). FIG. 7C is a plot of the XRD
data.
EXAMPLE 7
[0122] This examples illustrates production of a lithium-based
compound coated particle composition in accordance with an
embodiment of the present invention.
[0123] Carbon-coated LiFePO.sub.4 nanoparticle compositions were
produced in a milling process. The milling process used a mill and
multi-carbide material grinding media grinding media. About 30 g
LiFePO.sub.4 was mixed with 300 g of anhydrous isopropyl alcohol
(IPA) and 0.2% 3,6,9-trioxadecanoic acid within the mill to form a
slurry. The slurry was processed at a specific energy of 45,000
kJ/kg. A peristaltic pump was used with an agitator speed of 1320
rpm. Carbon-coated LiFePO.sub.4 nanoparticle compositions were
obtained.
[0124] The milled particles were characterized using several
techniques. The BET surface area was measured to be about 40
m.sup.2/g using a multi-point BET measurement instrument. Particle
size analysis was conducted using an SEM. The average particle size
was determined to be between about 30-50 nm, with the particles
having a platelet morphology. FIGS. 8A-B are copies of SEM images
showing a representative portion of the milled nanoparticle
composition. XRD analysis indicated that the carbon-coated
LiFePO.sub.4 nanoparticle composition had a crystal structure which
is identical to the crystal structure of the feed particles (prior
to milling). FIG. 8C is a plot of the XRD data.
* * * * *