U.S. patent application number 13/842978 was filed with the patent office on 2014-09-18 for complexometric precursor formulation methodology for industrial production of fine and ultrafine powders and nanopowders of layered lithium mixed metal oxides for battery applications.
This patent application is currently assigned to Perfect Lithium Corp. The applicant listed for this patent is Teresita Frianeza-Kullburg. Invention is credited to Teresita Frianeza-Kullburg.
Application Number | 20140272580 13/842978 |
Document ID | / |
Family ID | 51528472 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140272580 |
Kind Code |
A1 |
Frianeza-Kullburg;
Teresita |
September 18, 2014 |
Complexometric Precursor Formulation Methodology For Industrial
Production Of Fine And Ultrafine Powders And Nanopowders Of Layered
Lithium Mixed metal Oxides For Battery Applications
Abstract
A battery with improved properties is provided. The battery has
a cathode material prepared by the complexometric formulation
methodology comprising M.sub.jX.sub.p wherein: M.sub.j is at least
one positive ion selected from the group consisting of alkali
metals, alkaline earth metals and transition metals and n
represents the moles of said positive ion per mole of said
M.sub.jX.sub.p; and X.sub.p is a negative anion or polyanion
selected from Groups IIIA, IV A, VA, VIA and VIIA and may be one or
more anion or polyanion and p representing the moles of said
negative ion per moles of said M.sub.jX.sub.p. The battery has a
discharge capacity at the 1000.sup.th discharge cycle of at least
120 mAh/g at room temperature at a discharge rate of 1 C when
discharged from at least 4.6 volts to at least 2.0 volts.
Inventors: |
Frianeza-Kullburg; Teresita;
(Gastonia, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Frianeza-Kullburg; Teresita |
Gastonia |
NC |
US |
|
|
Assignee: |
Perfect Lithium Corp
|
Family ID: |
51528472 |
Appl. No.: |
13/842978 |
Filed: |
March 15, 2013 |
Current U.S.
Class: |
429/218.1 ;
252/182.1; 423/306; 423/593.1; 429/212 |
Current CPC
Class: |
H01M 4/5825 20130101;
H01M 4/0471 20130101; H01M 4/366 20130101; Y02E 60/10 20130101;
H01M 4/525 20130101; Y02P 70/50 20151101; H01M 4/485 20130101; H01M
10/052 20130101; H01M 4/505 20130101; H01M 10/0525 20130101 |
Class at
Publication: |
429/218.1 ;
429/212; 423/593.1; 423/306; 252/182.1 |
International
Class: |
H01M 4/36 20060101
H01M004/36; H01M 4/505 20060101 H01M004/505; H01M 4/58 20060101
H01M004/58; H01M 4/525 20060101 H01M004/525 |
Claims
1. A battery comprising: a cathode material prepared by the
complexometric formulation methodology comprising M.sub.j; wherein:
M.sub.j is at least one positive ion selected from the group
consisting of alkali metals, alkaline earth metals and transition
metals and j represents the moles of said positive ion per mole of
said M.sub.jX.sub.p; and X.sub.p is a negative anion or polyanion
selected from Groups IIIA, IV A, VA, VIA and VIIA and may be one or
more anion or polyanion and p representing the moles of said
negative ion per moles of said M.sub.jX.sub.p. wherein said battery
has a discharge capacity at the 1000.sup.th discharge cycle of at
least 120 mAh/g at room temperature at a discharge rate of 1 C when
discharged from at least 4.6 volts to at least 2.0 volts.
2. The battery of claim 1 wherein said M.sub.j comprises M.sub.1
and M.sub.2 and wherein M.sub.1 is lithium and M.sub.2 is a
transition metal.
3. The battery of claim 1 wherein said cathode material comprises
xLiMO.sub.2.(1-x)Li.sub.2M'O.sub.3 where M and M' are each at least
one transition metal and x is 0 to 1.
4. The battery of claim 3 wherein said transition metal is selected
from the group consisting of Ni, Mn and Co.
5. The battery of claim 1 wherein said cathode material comprises
Li.sub.2-x-y-zNi.sub.xMn.sub.yCo.sub.zO.sub.2 wherein x+y+z<1
and at least one of said x, y or z is not zero.
6. The battery of claim 5 wherein none of said x, y or z are
zero.
7. The battery of claim 1 wherein said cathode material is
Li.sub.2-x-y-z-aNi.sub.xMn.sub.yCo.sub.zD.sub.aO.sub.2 wherein
x+y+z<1 and none of said x, y or z are zero and D is a dopant
and a is mole fraction of D representing no more than 10 weight
percent.
8. The battery of claim 7 wherein said dopant is selected from the
group consisting of compounds of alkali or alkaline earth metals,
Group III A, IV A and transition metals.
9. The battery of claim 7 wherein said dopant is selected from the
group consisting of comprising hydroxides, oxides, fluorides,
phosphates, silicates and mixtures of these.
10. The battery of claim 1 wherein said cathode material is
Li.sub.2-x-y-z-aNi.sub.xMn.sub.yCo.sub.zD.sub.aO.sub.2-bX.sub.b
wherein x+y+z<1 and none of said x, y or z are zero; D is a
dopant; a is mole fraction of D representing no more than 10 weight
percent; X is an anion or polyanion other than oxide and b is 0 to
1.
11. The battery of claim 1 wherein said cathode material further
comprises a coating.
12. The battery of claim 11 wherein said coating comprises at least
one material selected from the group consisting of alkali earth
metal, alkaline earth metal, Group III A element, Group IV A
element and a transition metal.
13. The battery of claim 11 wherein said coating comprises an
organic or inorganic compound.
14. The battery of claim 11 wherein said coating is a
nanolayer.
15. The battery of claim 11 wherein said coating comprises carbon
or a carbon-containing compound.
16. The battery of claim 1 wherein said cathode material is a
nanostructure.
17. The battery of claim 16 wherein said nanostructure is a
nanocroissant, nanorose or nanohydrangea.
18. The battery of claim 1 wherein said cathode material has a
particle size of less than 1 micron.
19. The battery of claim 1 wherein said cathode material has an
average particle size of 200-300 nm.
20. The battery of claim 1 wherein said cathode material has a
surface area of at least 1 m.sup.2/gm.
21. The battery of claim 1 wherein said cathode material comprises
a lithium salt of at least one of Ni, Mn, Co, Ti, Mg, or Zn.
22. The battery of claim 21 wherein said lithium salt is
Li.sub.2-x-y-zNi.sub.xMn.sub.yCo.sub.zO.sub.2 wherein x+y+z<1
and none of said x, y or z are zero.
23. The battery of claim 21 wherein said lithium salt is
Li.sub.1.2Ni.sub.xMn.sub.yCo.sub.zO.sub.2 where 0.1<x<0.4,
0.4<y<0.65, and 0.05<z<0.3 and x+y+z=0.8.
24. The battery of claim 21 wherein said lithium salt is
Li.sub.1.2Ni.sub.xMn.sub.yCo.sub.zO.sub.2 where 0.45<y<0.55
and x+y+z=0.8.
25. The battery of claim 1 with a discharge capacity of at least
120 mAh/g at the 1000.sup.th discharge cycle at room temperature
and a discharge rate of 1 C from 4.6 to 2.5 volts.
Description
BACKGROUND
[0001] The present application is related to an improved method of
forming fine and ultrafine powders and nanopowders. More
specifically, the present invention is related to the formation of
fine and ultrafine powders and nanopowders through complexometric
precursors formed on bubble surfaces. Furthermore, this invention
describes the preparation of lithium metal oxide by complexometric
precursors that have excellent physical and chemical properties
required for high performance battery applications.
[0002] Our present society is advancing very rapidly in new
technologies especially in the areas of biotechnology, medicine,
electronics, pharmaceuticals and energy. These require significant
improvements in raw material processing and in the production of
high performance products of advanced chemical formulations without
compromising cost relative to commercial scale-up for industrial
production (FIG. 1). Thus, this requires a combination of
structure-processing-property correlations that will lead to
specialized high performance materials in order to sustain these
modern technically demanding criteria.
[0003] Starting with a desired specific application, the process
must be tailored to obtain the characteristics, both physical and
chemical, in order to meet the end performance result. It is
imperative to uniquely combine both well-established properties of
the compounds and/or raw materials with the new, unique, unusual or
desirable properties of the advanced materials. For example,
traditional ceramics are well-known to be electrical insulators yet
it is possible to utilize this property such that the special
ceramics will provide high thermal conductivity allowing their use
as heat sinks in substrates for microelectronics. Ceramic
composites of inorganic glass fibers and plastics have been used
for thermal and sound insulation traditionally but now are also
used as optical fibers replacing the traditional copper wire.
Ceramic engines replacing the traditional steel engines can
withstand higher temperatures and will burn energy more
effectively. This requires that the ceramics used for engine
manufacture be of very fine particles such that strength and
toughness to withstand the elevated temperatures and ruggedness
required for these applications. Furthermore, nanosize powders when
fabricated into the ceramic parts for these vehicles will be more
dense, have less defects, and can be fabricated in thinner and
smaller, lightweight sizes for practical use.
[0004] Increased energy consumption today necessitates discovery of
new resources but also improvement in current materials to satisfy
the energy infrastructure such as solar cells, fuel cells,
biofuels, and rechargeable batteries. For example, the lithium ion
battery that has been in use in consumer electronic devices but is
now commanding a significant role in larger transport vehicles.
These alternative energy resources must be more practical, and
price competitive with fossil fuels, for wider acceptability in
high-performance applications. As a consequence, sophisticated
devices require specially designed microstructures that will
enhance the physical and chemical properties of the materials
utilized. Often, these materials are more expensive to produce on
an industrial scale. Furthermore, these specialty powdered
materials such as oxides, phosphates, silicates and the like,
require not only a nanosize material but also a narrow particle
size distribution with high porosity, high surface area and other
characteristics to achieve enhanced performance. For instance, a
nanostructured lithium cathode powder for the lithium ion battery
would be expected to have improved mass and charge transport due to
shorter diffusion paths and higher amount of active sites resulting
from its finer smaller particle size. However, this added cost for
the added value may not be acceptable to the end consumer resulting
in reduced sales.
[0005] Other challenges are medical applications such as the use of
calcium phosphate for bone substitution. While several calcium
phosphate powders are available in the market, the requirements of
less than one micron discrete particles as described in U.S. Pat.
No. 8,329,762 B2 are important for making a biocompatible synthetic
bone. U.S. Pat. No. 5,714,103 describes bone implants based on
calcium phosphate hydraulic cements, called CHPCs, made of a
succession of stacked layers with a macroporous architecture
mimicking the natural porosity of spongious bone. This medical
field would definitely benefit from improved powders with better
performance and lower cost. Another example is a dermal patch
wherein the pharmaceutical drug is released to the body. Both
dermal patch and drug material combined would be more compatible if
their particle sizes were nanosize with narrow particle size
distribution. Nanopowders can also significantly impact high
performance dental applications, for example, such as teeth filling
materials as well as enamel coating materials to aesthetically
enhance and strengthen the tooth structure. In order to widen the
usage of nanomaterials in the medical field, both cost and
performance value should be compatible to both producer and
end-user.
[0006] Distinctive characteristics clearly differentiate between
advanced materials and traditional materials in several aspects,
notably in raw materials, processing, chemical and physical
characteristics, novel applications and specialized markets.
Conventional powder processes are made without strict chemical
control and are generally made from grinding and segregating
naturally occurring materials through physical means. These result
in neither ultrapure nor ultrahomogeneous particles such that
fabrication of a product using such heterogeneous and impure
substances gives grain boundary impurities that may reduce
mechanical strength or optical deformations and other limitations.
Chemical processing solves this problem by controlling the
composition of the powder at the molecular level to achieve a
special ultrastructure for the preferred performance application.
Specialized properties such as conductivity, electrochemical
capacity, optical clarity, dielectric value, magnetic strength,
toughness and strength are met only with specialized processing
methods to control microstructure. However, these demands
necessitate an economically commercial viable process for large
scale production. The dual requirements of cost and performance
must be met to successfully commercialize these advanced
materials.
[0007] A significant improvement in available raw materials is
needed to meet many objectives. One objective is high purity, no
longer 90% but >99% and even 99.999%, which entails chemical
processing to remove undesirable impurities that affect
performance. Another objective is particle size which preferably
has a narrow, homogeneous particle size distribution with finer
particle sizes of no longer 50 microns but 1 micron and preferably,
nanosize. The addition of dopants which are deemed to enhance the
specialized properties, like electronic conductivity and others,
must be homogeneously distributed but also preferably distributed
on the surface of the powder in some applications. Cobalt, aluminum
and gadolinium are suitable dopants. Other dopants include Ti, Zr,
Mg, Ca, Sr, Ba, Mg, Cr and B.
[0008] Innovations in processing these advanced materials to the
final product are also necessary. As such, combinations of
different processing techniques are often utilized. For example,
inorganic powders have been usually made by traditional ceramics
like solid state sintering. However, the resulting powder obtained
by this method alone generally has a wider and larger particle size
distribution. To obtain a homogeneous nanosize distribution,
several grinding and milling steps have been employed. The generic
types are ball mills, rod mills, vibratory mills, attrition mills,
and jet mills. Disadvantages of these methods include energy and
labor intensive production cycles and possibility of contamination
from grinding balls utilized. Defects in the microstructure also
occur causing degradation in the required performance targets.
Chemical vapor deposition, emulsion evaporation, precipitation
methods, hydrothermal synthesis, sol-gel, precipitation, spray
drying, spray pyrolysis and freeze drying are some of the other
methods used for these types of preparations, each with advantages
and disadvantages.
[0009] The technical drivers today call for particles less than one
micron, and even to less than 100 nanometers. To date, the
significance of the initial powder synthesis steps have been
overlooked but these initial reactions clearly define the final
finished powder microstructure and also determines scalability
controls and finally, cost and performance. Careful selection of
the starting reactants and the media--solid, liquid or gas--plays a
unique role in the formulation of low cost, high performance
powders.
[0010] An example is the formation of colloidal consolidated
structures by initial dispersion of particles in a liquid medium.
When the particle concentration is low, dispersed colloidal
suspensions can be used to eliminate flow units larger than a
certain size through sedimentation or classification. The surface
chemistry of the particles can be modified through the adsorption
of surfactants. The mixing of multiphase systems can be achieved at
the scale of the primary particle size. Once the desired
modifications are achieved, the transition from dispersed to
consolidated structure is accomplished by either increasing the
particle-particle attraction forces, such as by flocculation, or by
increasing the solids content of the suspension for forced
flocculation. This whole process results in going from a fluid
state ("slip") to a solid phase transition ("cast"). While this has
been found to occur in the micron to sub-micron size range, highly
concentrated suspensions with nanometer size particles have not
been as successful. Thus, some innovation is needed in traditional
colloidal techniques in order to achieve nanosize powders.
[0011] Such nanoparticles possess crystalline properties and other
nanoscale features that dramatically result in unique mechanical,
magnetic, thermal, optical, biological, chemical and electrical
properties. Considerable growth is expected in all these markets.
Therefore, achievement of an economically viable industrial
production of these specialized materials entails innovations in
conventional processing techniques and distinct improvements in
present industrial equipment.
[0012] Traditionally, powders are made using a solid state route.
By this method, the raw materials are ground and milled to the same
size and with a narrow size distribution, blended and fired to
obtain the final product as shown:
A solid+B solid.fwdarw.C solid product
[0013] In U.S. Pat. No. 6,277,521 B1, Manev et al. describe the
preparation of lithium metal oxides such as
LiNi.sub.1-xCo.sub.yM.sub..alpha.M'.sub..beta.O.sub.2 where M is Ti
or Zr and M' is Mg, Ca, Sr, Ba, and combinations thereof. To
prepare LiNi.sub.0.7Co.sub.0.2Ti.sub.0.05Mg.sub.0.05O.sub.2,
stoichiometric amounts off LiOH, NiO, Co.sub.3O.sub.4, TiO.sub.2
and Mg(OH).sub.2 are weighed, mixed and fired for 10 hours at
550.degree. C. followed for an additional 10 hours at 800.degree.
C. Milling after the firing step is done to produce the fine
powders of micron size. Furthermore, to obtain a narrow particle
distribution, sizing selection is also done in line with the
milling step. Larger size fractions are then re-milled.
[0014] One of the problems with obtaining nanopowders via the solid
state method is the considerable milling process that can be time
and labor intensive. The quality of the final product is a function
of time, temperature and milling energy. Achieving nanometer grain
sizes of narrow size distribution requires relatively long
processing times in smaller batches, not just for the final
sintered product but also for the starting materials, as these
materials should have particle sizes within the same distribution
for them to blend more homogeneously in order to have the right
stoichiometry in the final product. Hence, it may become necessary
to correct the stoichiometries of the final product after firing by
reblending additional starting raw materials and then refiring. As
a result, successive calcinations make the processing time longer
and more energy intensive which increases production cost.
Production of nanopowders by mechanical attrition is a structural
decomposition of the coarser grains by severe plastic deformation
instead of by controlled cluster assembly that yields not only the
right particle size and the required homogeneous narrow size
distribution but also significant nanostructures or microstructures
needed for effective performance benchmarks. As such, some higher
performance standards required for specialized applications are not
attained. C. C. Koch addresses these issues in his article
"Synthesis of Nanostructured Materials by Mechanical Milling
Problems and Opportunities", Nanostructured Materials, Vol. 9, pp
13-22, 1997.
[0015] Obtaining fine powders and nanopowders by milling has
improved with modern grinding machines such as stirred ball mills
and vibration mills for wet grinding or jet mills for dry grinding
processes. However, achieving a narrow particle size distribution
still remains a difficult task today. Classifiers have to be
integrated with the milling system and this repetitive sizing and
milling procedures increase the processing time in making fine
powders and even much longer for nanopowders. Another drawback is
potential contamination of the final product from the milling media
used. U.S. Pat. No. 7,578,457 B2, to R. Dobbs uses grinding media,
ranging in size from 0.5 micron to 100 mm in diameter, formed from
a multi-carbide material consisting of two or more carbide forming
elements and carbon. These elements are selected from the group
consisting of Cr, Hf, Nb, Ta, Ti, W, Mo, V, Zr. In US Patent
Application No. 2009/0212267 A1, a method for making small
particles for use as electrodes comprises using a first particle
precursor and a second particle precursor, milling each of these
precursors to an average size of less than 100 nm before reacting
to at least 500.degree. C. As an example, to make lithium iron
phosphate, one precursor is aluminum nitrate, ammonium dihydrogen
phosphate and the like and the other precursor is lithium
carbonate, lithium dihydrogen phosphate and the like. In US Patent
Application No. 2008/0280141 A1, grinding media with density
greater than 8 g/mL and media size from 75-150 microns was
specially made for the desired nanosize specification and the
hardness of the powder to be milled. The premise is that finer,
smaller size, specialized grinding media can deliver the preferred
nanosize particles. Time and energy consumption are high using this
modified solid state route to nanopowders. Moreover, after milling,
the grinding media and the nanopowders must be separated. Since
nanopowders are a health risk if inhaled, the separation will have
to be done under wet conditions. The wet powders will then have to
be dried again which adds to the number of processing steps.
[0016] Chemical vapor deposition, physical vapor deposition, plasma
synthesis are all synthesis of powders in the gas phase. In this
process, the starting raw materials are vaporized in the gas phase
then collected in a cooling step on a chosen substrate. Controlled
nucleation yields excellent powders that easily meet the rigorous
requirements for specialized applications but the cost of the
energy source and the equipment required for this method can
significantly impact the final cost of the powder. More information
on these processes is discussed by H. H. Hahn in "Gas Phase
Synthesis of Nanocrystalline Materials, "Nanostructured Materials,
Vol. 9, pp 3-12, 1997. Powders for the semiconductor industry are
usually made by this type of processing.
[0017] In U.S. Pat. No. 8,147,793 B2, S. Put et al. disclose a
method of preparing nano-sized metal bearing powders and doped
powders by using a non-volatile metal bearing precursor and
dispersing this precursor in a hot gas stream. This hot gas stream
may be generated by a flame burner or a DC plasma arc with nitrogen
as a plasma gas, for example. Thus, coarse size ZnO powder that is
injected is reduced to Zn vapor. When air is introduced, Zn is
oxidized to ZnO with nano-size particles.
[0018] Among the wet solution methods for fine powder synthesis are
precipitation, sol-gel, and variants of these using complexing
agents, emulsifiers and/or surfactants. In WO 2010/042434 A2,
Venkatachalam et al. describe a co-precipitation process involving
metal hydroxides and sol-gel approaches for the preparation of
Li.sub.1+xNi.sub..alpha.Mn.sub..beta.Co.sub..gamma.M.sub..delta.O.sub.2-.-
alpha.F.sub.z where M is Mg, Zn, Al, Ga, B, Zr, Ca, Ce, Ti, Nb or
combinations thereof. In one example cited, stoichiometric amounts
of nickel acetate, cobalt acetate, and manganese acetate were
dissolved in distilled water to form a mixed metal acetate solution
under oxygen-free atmosphere. This mixed metal acetate solution was
added to a stirred solution of lithium hydroxide to precipitate the
mixed metal hydroxides. After filtration, washing to remove
residual Li and base, and drying under nitrogen atmosphere, the
mixed metal hydroxides were mixed with the appropriate amount of
lithium hydroxide powder in a jar mill, double planetary mixer or a
dry powder mixer. The mixed powders were calcined at 400.degree. C.
for 8 hours in air, cooling, additional mixing, homogenizing in the
mill or mixer, and then recalcined at 900.degree. C. for 12 hours
to form the final product
Li.sub.1.2Ni.sub.0.175Co.sub.0.10Mn.sub.0.525O.sub.2. The total
time from start to finish for their method is 20 hours for the
calcination step alone plus the cooling time, the times for the
initial mixed metal hydroxide precipitation, milling and blending
to homogenize, and the filtration and washing steps. All these
process steps add up to a calcination time of 20 hours excluding
the cooling time for the furnace and the time from the other
processing steps which will have a combined total of at least 30
hours or more. Furthermore, in their process, the second part after
the co-precipitation is a solid state method since the mixed metal
hydroxides and the lithium hydroxides are mixed and then fired. The
final calcined powder size obtained from a solid state route is
usually in the micron size range which will entail additional
intensive milling to reduce the particles to a homogeneous narrow
size distribution of nanopowders. This processing has numerous
steps to obtain the final product which can impact large scale
production costs.
[0019] Another example of co-precipitation is described in U.S.
Pat. No. 6,241,959 B1. Nitrates of nickel, cobalt and magnesium
were mixed in a mole ratio of 0.79:0.19:0.02 and dissolved in
solution. Aqueous ammonia was added to precipitate the hydroxides
and the pH was further adjusted using 6M NaOH till pH 11. After 6
hours of addition time, the Ni--Co composite hydroxide was
separated. Lithium hydroxide was mixed with this Ni--Co hydroxide
and heated to 400.degree. C. and maintained at this temperature for
6 hours. After cooling, the product was then reheated to
750.degree. C. for 16 hours. The battery cycling test was done at a
low C rate of 0.2 C. Discharge capacity was 160 mAh/g. Only 30
cycles were shown. Note that the coprecipitation process is only
for the Ni--Co hydroxides. The second part of this process is a
solid state synthesis where the starting raw materials, Ni--Co
hydroxide and the lithium hydroxide are mixed and then fired. The
addition of NaOH to raise the pH to 11 as well as provide a source
of hydroxide ions would leave residual Na ions in the final product
unless the excess Na.sup.+ is washed off. This excess Na.sup.+ will
affect the purity of the material and have some deleterious effect
in the battery performance. The total process time is 6 hours
addition time for the co-precipitation step, 22 total hours for the
holding time at the two heating steps and additional time for the
other steps of cooling, separating, mixing and others which sums up
to at least 40 hours of processing time.
[0020] Sol-gel synthesis is a variant of the precipitation method.
This involves hydrolysis followed by condensation to form uniform
fine powders. The raw materials are expensive and the reaction is
slow since the hydrolysis-condensation reactions must be carefully
controlled. Alkoxides are usually the choice and these are also air
sensitive; thus requiring the reactions to be under controlled
atmosphere.
[0021] Hydrothermal synthesis has also been used to prepare these
powders. This involves crystallization of aqueous solutions at high
temperature and high pressures. An example of this process is
disclosed in US Patent Publication No. 2010/0227221 A1. A lithium
metal composite oxide was prepared by mixing an aqueous solution of
one or more transition metal cations with an alkalifying agent and
another lithium compound to precipitate the hydroxides. Water is
then added to this mixture under supercritical or subcritical
conditions, dried then followed by calcining and granulating then
another calcining step to synthesize the lithium metal oxide. The
water under supercritical or subcritical conditions has a pressure
of 180-550 bar and a temperature of 200-700.degree. C.
[0022] The use of agents like emulsifiers, surfactants, and
complexing agents to form nanosize powders has been demonstrated.
In microemulsion methods, inorganic reactions are confined to
aqueous domains called water-in-oil or surfactant/water/oil
combination. A problem is separation of the product particle from
the oil since filtration of a nanosize particle is difficult.
Reaction times are long. Residual oil and surfactant that remain
after the separation still have to be removed by other means such
as heating. As a result, the batch sizes are small.
[0023] A variety of structures are formed by the surfactant with
another particle dispersed in solution. Micelles are formed at high
concentrations of the surfactant and the micelle diameter is
determined by the length of the surfactant chain which can be from
20-300 angstroms. U.S. Pat. No. 6,752,979 B1 describes a way of
making metal oxide particles with nano-sized grains using
surfactants. A concentrated aqueous solution of at least one or
more metal cations of at least 90% of its solubility is mixed with
surfactant to form micelles at a given temperature. Optionally,
this micellar liquid forms a gel. This mixture is heated to form
the metal oxide and remove the surfactant. A disadvantage is the
long heat treatment times.
[0024] U.S. Pat. No. 6,383,285 B1 discloses a method for making
cathode materials for lithium ion batteries using a lithium salt, a
transition metal salt, and a complexing agent in water then
removing water by spray-drying to form a precursor. These
complexing agents were citric acid, oxalic acid, malonic acid,
tartaric acid, maleic acid and succinic acid. The use of these
agents increases the processing cost of the product. The precursor
is formed from the lithium, transition metal and the complexing
agent after spray drying. Battery capacities were only given for
the first cycle. The C- rate was not defined. For electric vehicle
applications, lithium ion battery performance at high C- rate for
many cycles is an important criterion.
[0025] A method for making lithium vanadium phosphate was described
in US Patent Publication No. 2009/0148377 A1. A phosphate ion
source, a lithium compound, V.sub.2O.sub.5, a polymeric material,
solvent, and a source of carbon or organic material were mixed to
form a slurry. This wet blended slurry was then spray dried to form
a precursor which was then milled, compacted, pre-baked and
calcined for about 8 hours at 900.degree. C. The particle size
after spray drying was about 50-100 microns. The final product was
milled to 20 microns using a fluidized bed jet mill.
[0026] Nanosize Li.sub.4Ti.sub.5O.sub.12 was prepared by preparing
this lithium titanate as a first size between 5 nm to 2000 nm as
described in U.S. Pat. No. 6,890,510 B2 from a blend of titanium
and lithium, evaporating and calcining this blend, milling this
powder to a finer size, spray drying then refiring this lithium
titanate, then milling again. There are several milling and firing
sequences in this process to obtain the nanosize desired which
increase the number of processing steps which consequently
increases the cost of processing.
[0027] Lithium ion batteries have proven their commercial
practicality since the early 1990s when Sony first introduced this
battery for its consumer electronics. The cathode material used
then was lithium cobalt oxide whose layered structure allowed the
Li+ ions to effectively intercalate between the cathode and the
anode. Moreover, the battery was lightweight and without any memory
effect, compared with the other rechargeable batteries like the
NiCd or the NiMH batteries. Its energy density was 3-4 times more
than currently available rechargeable batteries.
[0028] The start of commercialization of the lithium ion battery
using lithium cobalt oxide has benefited many applications. Its
reputation for safety in consumer devices has promoted other
potential applications, most notably in the transportation
industry. Our current consumption of oil has increased
significantly and such dependence has spurred more investigation
into alternative sources of energy. That direction focused into
developing the lithium ion battery for high load, high power
applications and this required developing and investigating new
materials for use as a cathode for the lithium ion battery.
Attention was generated towards research into the cost, safety and
reliability of lithium cathode materials.
[0029] The first row of transition metals and those similar to the
cobalt ion in chemical and physical properties were Ni, Mn and Fe
as well as V. These compounds were synthesized generally using the
traditional solid state route. Nickel is a good substitute for
cobalt and has a layered structure. Its use in the NiCd and NiMH
rechargeable batteries has proven its capability. However, its
excellent conductivity also caused some safety problems in the
lithium ion battery. Cobalt is an expensive metal but has proven
reliability by its established battery performance in commercial
lithium ion batteries for many years. Manganese, as a spinel
structure LiMn.sub.2O.sub.4, is least expensive but it has a
disadvantage of not having high conductivity. Iron as LiFeO.sub.2
did not have the battery performance required but as olivine
structure LiFePO.sub.4, it has proven its use in high power
applications. A layered-layered structure,
xLiMn.sub.2O.sub.3.(1-x)LMO.sub.2,where M=Co,Ni,Mn
has taken considerable interest since it has exhibited good battery
performance. Other research is ongoing extensively on combinations
of Co, Ni, Mn and Fe, including the addition of dopants or coatings
to create some surface modifications that would lead to thermal
stability and/or chemical stability which would then extend cycle
life.
[0030] Today, synthesizing an alternative lithium metal oxide or
other lithium metal compound as cathode material for electric
vehicle applications remains a chemical challenge. The
transportation requirements are significantly more demanding than
consumer electronic devices. These issues include cycle life
especially under extreme temperature conditions, charging times,
miles driven per charge, miles driven per charge per speed, total
vehicle battery cost, battery cycle life, durability, and safety.
The preferred lithium cathode material will have to be produced
industrially in large scale. Therefore, the processing conditions
must produce the physical and chemical characteristics of this
preferred lithium cathode material at low cost. Starting materials
should be of high purity, preferably with low Na, Cl and S and
other contaminants detrimental to the battery yet be low cost.
Production equipment must be currently available equipment already
in use with novel innovations easily implemented. Finally, the
number of processing steps should be decreased as well as be less
energy and labor intensive.
[0031] The desired properties of this preferred lithium cathode
material are; namely: 1.) high capacity, 2.) long cycle life, 3.)
high stability, 4.) fast charging rate, 5.) low cost. The physical
properties should include the following; namely: 1.) fine particle
size, 2.) narrow particle size distribution, 3.) uniform
morphology, 4.) high purity, 5.) high surface area, 6.) optimum
degree of crystallization, 7.) minimum defects and 8.) minimum
agglomeration. In order to achieve all these at low cost or
acceptable consumer cost requires a balance in the preparation of
this preferred lithium cathode. Nanoparticles have been of
significant interest but the cost of achieving nanosize powders
remains a significant cost in production.
[0032] This invention aims to achieve this preferred high
performance lithium cathode material by using the complexometric
precursor formulation methodology in the synthesis of this lithium
cathode material. The results described in this invention show that
the materials produced by a complexcelle formed during the CPF
process outperform cathodes currently in commercial use. The
objective is to industrially and cost-effectively produce these
preferred lithium cathode nanomaterials for energy storage systems
by the complexometric precursor formulation methodology. As such,
new avenues in battery technology will open and be easily
commercialized. Furthermore, these novel nanomaterials will have an
impact in other future energy systems and other potential
applications in other industries.
SUMMARY OF THE INVENTION
[0033] It is the objective of this invention to describe an
economically scalable process useful for several high value-added
inorganic powders tailored to meet the desired performance
specifications. It is a further objective of this invention to
produce the selected narrow size particle distribution of these
powders and to produce the desired particle size needed for the
selected application, such size ranging from fine micron size
particles to ultrafine powders and the nanosize powders. It is also
the objective of this invention to produce these powders that meet
or exceed presently available materials. It is the objective of
this invention to prepare lithium metal oxide powders by
complexometric precursor formulation methodology to achieve
tailored physical and chemical properties for high performance
lithium battery applications.
[0034] It is an object of this invention to provide a methodology
for industrial production of special fine, ultrafine and nano
powders without compromising performance.
[0035] A particular advantage of the invention is the ability to
prepare fine, ultrafine and nano-powders in large scale
production.
[0036] It is an object of the invention to produce these
specialized powders that outperform presently available
powders.
[0037] It is an object of the invention to utilize low cost
starting raw materials and to incorporate any purification within
the process steps as required.
[0038] These and other advantages, as will be realized, are
provided in a method of forming a powder M.sub.jX.sub.p wherein
M.sub.j is a positive ion or several positive ions selected from
alkali metal, alkaline earth metal or transition metal; and X.sub.p
is a monoatomic or a polyatomic anion selected from Groups IIIA,
IVA, VA, VIA or VIIA; called complexometric precursor formulation
or CPF. The method includes the steps of:
providing a first reactor vessel with a first gas diffuser and an
first agitator; providing a second reactor vessel with a second gas
diffuser and a second agitator; charging the first reactor vessel
with a first solution comprising a first salt of M.sub.jX.sub.p;
introducing gas into the first solution through the first gas
diffuser, charging the second reactor vessel with a second solution
comprising a second salt of M.sub.jX.sub.p; adding the second
solution to the first solution to form a complexcelle; drying the
complexcelle, to obtain a dry powder; and calcining the dried
powder of said M.sub.jX.sub.p.
[0039] Yet another embodiment is provided in a compound
M.sub.jX.sub.p prepared by the complexometric precursor formulation
methodology wherein:
M.sub.j is at least one positive ion selected from the group
consisting of alkali metals, alkaline earth metals and transition
metals and j is an integer representing the moles of said positive
ion per moles of said M.sub.jX.sub.p; and X.sub.p, a negative anion
or polyanion from Groups IIIA, IV A, VA, VIA and VIIA and may be
one or more anion or polyanion and p is an integer representing the
moles of said negative ion per moles of said M.sub.jX.sub.p.
[0040] Yet another embodiment is provided in a battery with
improved properties. The battery has a cathode material prepared by
the complexometric formulation methodology comprising
M.sub.nX.sub.p wherein: M.sub.j is at least one positive ion
selected from the group consisting of alkali metals, alkaline earth
metals and transition metals and n represents the moles of said
positive ion per mole of said M.sub.jX.sub.p; and X.sub.p is a
negative anion or polyanion selected from Groups IIIA, IV A, VA,
VIA and VIIA and may be one or more anion or polyanion and p
representing the moles of said negative ion per moles of said
M.sub.jX.sub.p. The battery has a discharge capacity at the
1000.sup.th discharge cycle of at least 120 mAh/g at room
temperature at a discharge rate of 1 C when discharged from at
least 4.6 volts to at least 2.0 volts.
FIGURES
[0041] FIG. 1 is a diagram of advanced technical materials which
require specialized processing to obtain composites, whiskers,
fibers and powders.
[0042] FIG. 2 is a comparison of preparative methods for
powders.
[0043] FIG. 3 is a flow chart of two reactants via the
complexometric precursor formulation methodology for the synthesis
of specialized powders.
[0044] FIG. 4 illustrates of a reactor vessel with gas inlet tubes
and agitator with special blades.
[0045] FIG. 5A schematically illustrates agitator blades with wound
concentric rings.
[0046] FIG. 5B is a side schematic partial view of the concentric
rings of the agitator blade.
[0047] FIG. 5C schematically illustrates one set of propellers with
three blades, concentric rings are not shown, attached to the mixer
shaft, each blade rotating on its own axis horizontally and
vertically on the mixer axis.
[0048] FIG. 5D schematically illustrates two sets of propellers
with three blades arranged on the mixer shaft.
[0049] FIG. 5E schematically illustrates one set of propellers with
three blades arranges alternately on the mixer shaft.
[0050] FIG. 5F schematically illustrates one set of propellers with
four blades on the mixer shaft.
[0051] FIG. 5G schematically illustrates one set of propellers with
four blades arranged alternately on the shaft of the reactor.
[0052] FIG. 6A schematically illustrates a bubble surface above the
bulk of the solution showing small and large bubbles.
[0053] FIG. 6B is a top schematic view of the bubble surface
interface showing the reactants on the surface interface.
[0054] FIG. 7 is a schematic representation of the steps during
complexcelle formation and separation from the bulk of the
solution.
[0055] FIG. 8A is a scanning electron micrograph at 5000.times. of
a commercial LiCoO.sub.2 in Example 1.
[0056] FIG. 8B is a scanning electron micrograph at 25000.times. of
a commercial LiCoO.sub.2 in Example 1.
[0057] FIG. 9 is an x-ray powder diffraction pattern of a
commercial LiCoO.sub.2 in Example 1.
[0058] FIG. 10 is a scanning electron micrograph at 5000.times. of
air dried LiCoO.sub.2 feed precursor to the spray dryer for Example
2.
[0059] FIG. 11A is a scanning electron micrograph at 10000.times.
of spray dried LiCoO.sub.2 described in Example 2 prior to
calcination.
[0060] FIG. 11B is a scanning electron micrograph at 25000.times.
of spray dried LiCoO2 described in Example 2 prior to
calcination.
[0061] FIG. 12 is a scanning electron micrograph at 10000.times. of
spray dried LiCoO.sub.2 described in Example 2 after
calcination.
[0062] FIG. 13 is an x-ray powder diffraction pattern of
LiCoO.sub.2 in Example 1.
[0063] FIG. 14 is battery cycling data for Examples 1 and 2 at C/20
for 500 cycles.
[0064] FIG. 15 is battery cycling data at 1 C for 500 cycles for
Examples 1 and 2 after recalcination for 5 h at 900.degree. C.
[0065] FIG. 16 is a scanning electron micrograph at 10000.times. of
recalcined LiCoO.sub.2 from Example 2.
[0066] FIG. 17 is a scanning electron micrograph at 10000.times. of
recalcined commercial LiCoO.sub.2 from Example 1.
[0067] FIG. 18A is a scanning electron micrograph at 2000.times. of
air-dried Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2 from
Example 4.
[0068] FIG. 18B is a scanning electron micrograph at 10000.times.
of air-dried Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2
from Example 4.
[0069] FIG. 19A is a scanning electron micrograph at 5000.times. of
spray dried Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2
from Example 4.
[0070] FIG. 19B is a scanning electron micrograph at 10000.times.
of spray dried Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2
from Example 4.
[0071] FIG. 20A is a scanning electron micrograph at 10000.times.
of calcined Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2
from Example 4.
[0072] FIG. 20B is a scanning electron micrograph at 25000.times.
of calcined Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2
from Example 4.
[0073] FIG. 21 is an x-ray powder diffraction pattern of calcined
Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2 from Example
4.
[0074] FIG. 22 is battery Cycling Data for calcined
Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2 from Example 4
at RT for 500 cycles at 1 C.
[0075] FIG. 23A is battery Cycling Data for calcined
Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2 from Example 4
at 30.degree. C. for 500 cycles at different C rates from C/20 to 1
C.
[0076] FIG. 23B is battery Cycling Data for calcined
Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2 from Example 4
at 30.degree. C. for 500 cycles at different C rates from C/10, C/3
and 1 C.
[0077] FIG. 24A is battery Cycling Data for calcined
Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2 from Example 4
at 25.degree. C. for 500 cycles at from C/20 to 1 C.
[0078] FIG. 24B is battery Cycling Data for calcined
Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2 from Example 4
at 25.degree. C. for 500 cycles at 1 C.
[0079] FIG. 25A is a scanning electron micrograph at 2000.times. of
spray dried LiCoO.sub.2 from Example 6.
[0080] FIG. 25B is a scanning electron micrograph at 10000.times.
of spray dried LiCoO.sub.2 from Example 6.
[0081] FIG. 26 is a scanning electron micrograph at 10000.times. of
calcined LiCoO.sub.2 from Example 6.
[0082] FIG. 27 is an X-ray powder diffraction pattern of
LiCoO.sub.2 in Example 6.
[0083] FIG. 28 is the battery cycling data for LiCoO.sub.2 of
Example 6 at C/20 for 50 cycles.
[0084] FIG. 29 is an X-ray powder diffraction pattern of
LiCoO.sub.2 after calcination for 5 h at 900.degree. C. in Example
7.
[0085] FIG. 30A is a scanning electron micrograph at 5000.times. of
calcined LiCoO.sub.2 from Example 7.
[0086] FIG. 30B is a scanning electron micrograph at 10000.times.
of calcined LiCoO.sub.2 from Example 7.
[0087] FIG. 30C is a scanning electron micrograph at 25000.times.
of calcined LiCoO.sub.2 from Example 7.
[0088] FIG. 31 is the battery cycling data for LiCoO.sub.2 of
Example 7 and the commercial sample at 1 C for 50 cycles at RT.
[0089] FIG. 32 is an X-ray powder diffraction pattern of
LiCoO.sub.2 fired two times for 5 h at 900.degree. C. in Example
8.
[0090] FIG. 33A is a scanning electron micrograph at 5000.times. of
recalcined LiCoO.sub.2 from Example 8.
[0091] FIG. 33B is a scanning electron micrograph at 10000.times.
of recalcined LiCoO.sub.2 from Example 8.
[0092] FIG. 33C is a scanning electron micrograph at 25000.times.
of recalcined LiCoO.sub.2 from Example 8.
[0093] FIG. 34 is the battery cycling data for LiCoO.sub.2 of
Example 8 and the refired commercial sample in Example 3 at 1 C for
500 cycles at RT.
[0094] FIG. 35 is a scanning electron micrograph at 20000.times. of
spray dried Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2
from Example 11.
[0095] FIG. 36A is a scanning electron micrograph at 20000.times.
of Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 from Example
11 calcined at 900.degree. C. for 5 h.
[0096] FIG. 36B is a scanning electron micrograph at 20000.times.
of Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 from Example
11 calcined at 900.degree. C. for 5 h two successive periods.
[0097] FIG. 36C is a scanning electron micrograph at 20000.times.
of Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 from Example
11 calcined at 900.degree. C. for 5 h for three successive
periods.
[0098] FIG. 37 is a transmission electron micrograph of
Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 from Example 11
calcined at 900.degree. C. for 5 h for three successive
periods.
[0099] FIG. 38A is an X-ray powder diffraction pattern of
Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 from Example 11
calcined at 900.degree. C. for 5 h.
[0100] FIG. 38B is an X-ray powder diffraction pattern of
Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 from Example 11
calcined at 900.degree. C. for 5 h for two successive periods.
[0101] FIG. 39A is the battery cycling data at RT for 500 cycles
for Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 from
Example 11 calcined at 900.degree. C. for 5 h.
[0102] FIG. 39B is the battery cycling data at RT for 500 cycles
for Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 from
Example 11 calcined at 900.degree. C. for 5 h for two successive
periods.
[0103] FIG. 40 is an X-ray powder diffraction pattern of
Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 from Example 11
calcined at 900.degree. C. for 5 h for three successive
periods.
[0104] FIG. 41 is the battery cycling data at RT for 1000 cycles
for Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 from
Example 11 calcined at 900.degree. C. for 5 h for three successive
periods.
[0105] FIG. 42A is an X-ray powder diffraction pattern of
Li.sub.1.20Ni.sub.0.17Mn.sub.0.51Co.sub.0.12O.sub.2 from Example 12
calcined at 900.degree. C. for 5 h.
[0106] FIG. 42B is an X-ray powder diffraction pattern of
Li.sub.1.20Ni.sub.0.17Mn.sub.0.51Co.sub.0.12O.sub.2 from Example 12
calcined at 900.degree. C. for 5 h for two successive periods.
[0107] FIG. 43A is a scanning electron micrograph at 20000.times.
of Li.sub.1.20Ni.sub.0.17Mn.sub.0.51Co.sub.0.12O.sub.2 from Example
12 calcined at 900.degree. C. for 5 h.
[0108] FIG. 43B is a scanning electron micrograph at 20000.times.
of Li.sub.1.20Ni.sub.0.17Mn.sub.0.51Co.sub.0.12O.sub.2 from Example
12 calcined at 900.degree. C. for 5 h for two successive
periods.
[0109] FIG. 44A is the battery cycling data at RT for 500 cycles
for Li.sub.1.20Ni.sub.0.17Mn.sub.0.51Co.sub.0.12O.sub.2 from
Example 12 calcined at 900.degree. C. for 5 h.
[0110] FIG. 44B is the battery cycling data at RT for 500 cycles
for Li.sub.1.20Ni.sub.0.17Mn.sub.0.51Co.sub.0.12O.sub.2 from
Example 12 calcined at 900.degree. C. for 5 h for two successive
periods.
[0111] FIG. 45 is an X-ray powder diffraction pattern of
Li.sub.1.20Ni.sub.0.17Mn.sub.0.51Co.sub.0.12O.sub.2 from Example 13
calcined at 900.degree. C. for 5 h for three successive
periods.
[0112] FIG. 46 is a scanning electron micrograph at 20000.times. of
Li.sub.1.20Ni.sub.0.17Mn.sub.0.51CO.sub.0.12O.sub.2 from Example 13
calcined at 900.degree. C. for 5 h for three successive
periods.
[0113] FIG. 47 is the battery cycling data at RT for 500 cycles for
Li.sub.1.20Ni.sub.0.17Mn.sub.0.51CO.sub.0.12O.sub.2 from Example 13
calcined at 900.degree. C. for 5 h for three successive
periods.
[0114] FIG. 48A is a scanning electron micrograph at 5000.times. of
spray dried Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2
from Example 14.
[0115] FIG. 48B is a scanning electron micrograph at 10000.times.
of spray dried Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2
from Example 14.
[0116] FIG. 48C is a scanning electron micrograph at 20000.times.
of spray dried Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2
from Example 14.
[0117] FIG. 49A is a scanning electron micrograph at 20000.times.
of Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2 from Example
14 calcined at 900.degree. C. for 5 h.
[0118] FIG. 49B is a scanning electron micrograph at 20000.times.
of Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2 from Example
14 calcined at 900.degree. C. for 5 h for two successive
periods.
[0119] FIG. 50 is a transmission electron micrograph of
Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2 from Example 14
calcined at 900.degree. C. for 5 h for three successive
periods.
[0120] FIG. 51A is an X-ray powder diffraction pattern of
Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2 from Example 14
calcined at 900.degree. C. for 5 h.
[0121] FIG. 51B is an X-ray powder diffraction pattern of
Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2 from Example 14
calcined at 900.degree. C. for 5 h for two successive periods.
[0122] FIG. 52A is the battery cycling data at RT for 500 cycles
for Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2 from
Example 14 calcined at 900.degree. C. for 5 h.
[0123] FIG. 52B is the battery cycling data at RT for 500 cycles
for Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2 from
Example 14 calcined at 900.degree. C. for 5 h for two successive
periods.
DESCRIPTION
[0124] The instant invention is specific to an improved method of
forming nanoparticles. More specifically, the instant invention is
specific to a method of forming particles through formation of a
complexometric precursor formed on a bubble surface thereby
allowing for careful control of nucleation and crystal growth.
[0125] The invention will be described with reference to the
various figures which form an integral non-limiting component of
the disclosure. Throughout the disclosure similar elements will be
numbered accordingly.
[0126] This invention described herein is a complexometric
precursor formulation methodology, hereinafter referred to as
"CPF", suitable for large scale industrial production of high
performance fine, ultrafine and nanosize powders requiring defined
unique chemical and physical properties that are essential to meet
performance specifications for specialized applications.
[0127] A particularly suitable material formed by the CPF process
is a lithium nickel manganese cobalt compound defined by formula is
Li.sub.2-2x-2y-2zNi.sub.xMn.sub.yCo.sub.zO.sub.2 wherein
x+y+z.ltoreq.1 and at least one of x, y or z is not zero and more
preferably none of x, y or z is zero.
[0128] The CPF method proceeds in the formation of a complex
precursor, herein called complexcelle, on a bubble surface thereby
providing for the controlled formation of specialized
microstructures or nanostructures and a final product with particle
size, surface area, porosity, phase purity, chemical purity and
other essential characteristics tailored to satisfy performance
specifications. Powders produced by CPF are obtained with a reduced
number of processing steps relative to currently used technology
and can utilize presently available industrial equipment. CPF is
simple to implement and preferred design configurations are further
described and illustrated in FIGS. 4 and 5. CPF methodology is
applicable to any inorganic powder and organometallic powders with
electrophilic or nucleophilic ligands. The CPF procedure can use
low cost raw materials as the starting raw materials and if needed,
additional purification or separation can be done in-situ. Inert or
oxidative atmospheric conditions required for powder synthesis are
easily achieved with the equipment for this method. Temperatures
for the reactions forming the complexcelle are ambient or slightly
warm but preferably not more than 100.degree. C. The CPF process
can be a batch process or a continuous process wherein product is
moved from one piece of equipment to the next in sequence. A
comparison of traditional methods and other conventional processing
is diagrammed in FIG. 2 with this CPF methodology. Representative
examples are discussed and compared with commercially available
samples showing both physical properties and performance
improvements of powders synthesized using this CPF methodology.
[0129] The CPF method produces fine, ultrafine and nanosize powders
in a simple efficient way by integrating chemical principles of
crystallization, solubility, transition complex formation, phase
chemistry, acidity and basicity, aqueous chemistry, thermodynamics
and surface chemistry.
[0130] It is preferred to produce these powders with the selected
properties at the onset of the contact among the elements as these
are combined to make the desired compound. The time when
crystallization begins and, in particular, when the nucleation step
begins, is the most crucial stage of formation of nanosize powders.
A particular advantage provided by CPF is the ability to prepare
the nanosize particles at the onset of this nucleation step. The
solute molecules from the starting reactants are dispersed in a
given solvent and are in solution. At this instance, clusters begin
to form on the nanometer scale on the bubble surface under the
right conditions of temperature, supersaturation, and other
conditions. These clusters constitute the nuclei wherein the atoms
begin to arrange themselves in a defined and periodic manner which
later defines the crystal microstructure. Crystal size and shape
are macroscopic properties of the crystal resulting from the
internal crystal structure.
[0131] After the nucleation begins, crystal growth also starts and
both nucleation and crystal growth may occur simultaneously as long
as supersaturation exists. The rate of nucleation and growth is
determined by the existing supersaturation in the solution and
either nucleation or growth occurs over the other depending on the
supersaturation state. It is critical to define the concentrations
of the reactants required accordingly in order to tailor the
crystal size and shape. If nucleation dominates over growth, finer
crystal size will be obtained. The nucleation step is a very
critical step and the conditions of the reactions at this initial
step define the crystal obtained. By definition, nucleation is an
initial phase change in a small area such as crystal forming from a
liquid solution. It is a consequence of rapid local fluctuations on
a molecular scale in a homogeneous phase that is in a state of
metastable equilibrium. Total nucleation is the sum effect of two
categories of nucleation--primary and secondary. In primary
nucleation, crystals are formed where no crystals are present as
initiators. Secondary nucleation occurs when crystals are present
to start the nucleation process. It is this consideration of the
significance of the initial nucleation step that forms the basis
for this CPF methodology.
[0132] In the CPF methodology, the reactants are dissolved in a
solution preferably at ambient temperature or if needed, at a
slightly elevated temperature but preferably not more than
100.degree. C. Selection of inexpensive raw materials and the
proper solvent are important aspects of this invention. The purity
of the starting materials are also important since this will affect
the purity of the final product which may need specified purity
levels required for its performance specifications. As such, low
cost starting materials which can be purified during the
preparation process without significantly increasing the cost of
processing must be taken into consideration. For instance, if a
preferred starting raw material is a carbonate salt, one can start
with a chloride salt as most reactants from rock processing are
chloride salts. There may be some impurities in this chloride salt
that may need to be removed and depending on the ease of impurity
reduction, this chloride salt can be converted to the carbonate
salt and at the same time remove any impurity or reduce the
impurity levels.
[0133] CPF uses conventional equipment in an innovative way to
produce the nanosize nuclei required for the final product. CPF
utilizes a reactor fitted with a gas diffuser to introduce gas into
the solution thereby creating bubbles. An agitator vigorously
disperses the solution simultaneously with the bubble formation, as
the second reactant is introduced into the first solution. The
combination of gas flow and agitation provides a bubble surface.
The bubble surface serves as the interface of contact between the
molecules of the first solution and the molecules of the second
solution thereby providing a surface reaction.
[0134] A surface reaction is the adsorption of one or more
reactants from a gas, liquid or dissolved solid on a surface.
Adsorption may be a physical or chemical adsorption.
[0135] The CPF process creates a film of the adsorbate on the
bubble surface of the adsorbent. The bubble surface is the
adsorbent and the adsorbates are the reactants in the solution. As
illustrated in FIG. 6A, a bubble is formed from solution due to the
simultaneous introduction of gas and agitator speed. Different size
bubbles can be formed depending on gas flow rates. The size of the
bubbles defines the surface area of contact between the molecules
and this relates to the degree of nucleation which influences the
particle size.
[0136] In FIG. 6B, the top view of this complexcelle is shown
schematically. The complexcelle comprises gas bubble, 61, with a
bubble surface, 62, shown above the surface of the solution, 68.
The first reactant cation, 63, the first reactant anion, 64, the
second reactant cation, 65 and the second reactant anion, 66, are
all on the bubble surface. Solvent is not illustrated in the
schematic diagram but it is understood that the solvent molecules
are present. In FIG. 7, an illustration of this surface pathway is
diagrammed showing the start of bubble formation, 61, from the bulk
of the solution, the surface nucleation on the bubble surface, 62,
which forms the complexcelle having reactant ions, 63-66, and the
separation of this complexcelle from the bulk of the solution. The
water molecules, 67, or solvent molecules are shown. This is a very
dynamic state as the solution is vigorously and continuously mixed
during the time of the addition of the second reactant solution
into the first reactant solution. Furthermore, bubbles are formed
within the bulk of the solution and the general direction is for
these bubbles to move towards the top surface of the solution. The
agitation rate enhances the rise of these bubbles to the surface
and mixes the solution vigorously so that there is significant
turnover of these reactants and their bubbles allowing fresh
surface bubbles to continually be available for complexcelle
formation. It will be realized that the above mechanism is a
postulated mechanism and the present invention should not be
construed as being limited to this particular pathway.
[0137] It is preferred that the gas be introduced directly into the
solution without limit to the method of introduction. The gas can
be introduced into the solution within the reactor by having
several gas diffusers, such as tubes, located on the side of the
reactor, wherein the tubes have holes for the exit of the gas as
illustrated in FIG. 4. Another configuration is to have a double
wall reactor such that the gas passes through the interior wall of
the reactor. The bottom of the reactor can also have entry ports
for the gas. The gas can also be introduced through the agitator
shaft, creating the bubbles upon exiting. Several other
configurations are possible and the descriptions of these
arrangements given herein are not limited to these. Throughout the
description the point of gas being introduced into the liquid is a
gas diffuser.
[0138] In one embodiment an aerator can be used as a gas diffuser.
Gas diffusing aerators can be incorporated into the reactor.
Ceramic diffusing aerators which are either tube or dome-shaped are
particularly suitable for demonstration of the invention. The pore
structures of ceramic bubble diffusers produce relatively fine
small bubbles resulting in an extremely high gas to liquid
interface per cubic feet per minute (cfm) of gas supplied. This
ratio of high gas to liquid interface coupled with an increase in
contact time due to the slower rate of the fine bubbles accounts
for the higher transfer rates. The porosity of the ceramic is a key
factor in the formation of the bubble and significantly contributes
to the nucleation process. While not limited thereto for most
configurations a gas flow rate of at least one liter of gas per
liter of solution per minute is suitable for demonstration of the
invention.
[0139] A ceramic tube gas diffuser on the sides of the reactor wall
is particularly suitable for demonstration of the invention.
Several of these tubes may be placed in positions, preferably
equidistant from each other, to create bubbling more uniformly
throughout the reactor. The gas is preferably introduced into the
diffuser within the reactor through a fitting connected to the
header assembly which slightly pressurizes the chamber of the tube.
As the gas permeates through the ceramic diffuser body, fine
bubbles start being formed by the porous structure of the material
and the surface tension of the liquid on the exterior of the
ceramic tube. Once the surface tension is overcome, a minute bubble
is formed. This small bubble then rises through the liquid forming
an interface for transfer between gas and liquid before reaching
the surface of the liquid level.
[0140] A dome-shaped diffuser can be placed at the bottom of the
reactor or on the sides of the reactor. With dome shape diffusers a
plume of gas bubbles is created which is constantly rising to the
surface from the bottom providing a large reactive surface.
[0141] A membrane diffuser which closes when gas flow is not enough
to overcome the surface tension is suitable for demonstration of
the invention. This is useful to prevent any product powder from
being lost into the diffuser.
[0142] In order to have higher gas efficiencies and utilization, it
is preferred to reduce the gas flow and pressure and expend less
pumping energy. A diffuser can be configured such that for the same
volume of gas, smaller bubbles are formed with higher surface area
than if fewer larger bubbles are formed. The larger surface area
means that the gas dissolves faster in the liquid. This is
advantageous in solutions wherein the gas is also used to
solubilize the reactant by increasing its solubility in the
solution.
[0143] Smaller bubbles also rise more slowly than the larger
bubbles. This is due to the friction, or surface tension, between
the gas and the liquid. If these bubbles start from the same
position or depth in the reactor, the larger bubbles reach the
surface more quickly than several smaller bubbles. The smaller
bubbles will have more liquid as it rises. The bubble surface
interface between the two reactants determines the nucleation rate
and size can therefore be tailored by controlling the bubble size
formation.
[0144] Nozzles, preferably one way nozzles, can be used to
introduce gas into the solution reactor. The gas can be delivered
using a pump and the flow rate should be controlled such that the
desired bubbles and bubble rates are achieved. A jet nozzle
diffuser, preferably on at least one of the sides or bottom of the
reactor, is suitable for demonstration of the invention.
[0145] The rate of gas introduction is preferably sufficient to
increase the volume of the solution by at least 5% excluding the
action of the agitator. In most circumstances at least about one
liter of gas per liter of solution per minute is sufficient to
achieve adequate bubble formation. It is preferable to recycle the
gas back into the reactor.
[0146] Transfer of the second reactant solution into the first
reactor solution is preferably done using a tube attached to a pump
connecting the solution to be transferred to the reactor. The tube
into the reactor is preferably a tube with a single orifice or
several orifices of a chosen predetermined internal diameter such
that the diameter size can deliver a stream of the second solution
at a given rate. Atomizers with fine nozzles are suitable for
delivering the second solution into the reactor. The tip of this
transfer tube can comprise a showerhead thereby providing several
streams of the second solution reacting on several surface bubbles
simultaneously. Nucleation is influenced not only by the
concentration of the second solution but also by the instantaneous
concentration of this solution as it reaches the surface bubble
interface to form the complexcelle. In large scale production, the
rate of transfer is a time factor so the transfer rate should be
sufficiently rapid enough to produce the right size desired.
[0147] The agitator can be equipped with several propellers of
different configurations, each set comprising one or more
propellers placed at an angle to each other or on the same plane.
Furthermore, the mixer may have one or more sets of these
propellers. The objective is to create enough turbulence for rapid
bubble formation and turnover. Examples of the agitator
arrangements are shown in FIGS. 5 A-G but other similar formations
are also possible and not limited to these. The function of this
mixer is not only to insure homogeneity of the reaction mixture but
also to assist in the bubble surface interaction which further
influences the nucleation and is a determining factor in the size
of the final particle.
[0148] Straight paddles or angled paddles are suitable. The
dimensions and designs of these paddles determine the type of flow
of the solution and the direction of the flow. One preferred blade
design for CPF methodology is shown in FIG. 5 where the paddles
consist of concentric rings wired around the paddle that create a
frothing effect in the solution. In addition, the paddle can rotate
on its own axis as well as rotate vertically by the axis of the
mixer. This maximizes the bubbling effect even under slower
agitation speed. A speed of at least about 100 rotations per minute
(rpm's) is suitable for demonstration of the invention.
[0149] The CPF process steps are demonstrated in the following
examples below for a desired final product M.sub.jX.sub.p such that
M=M.sub.1 M.sub.2 M.sub.3 (dual metal cation) or more and
X.sub.p.dbd.O. The flow chart in FIG. 3 shows a schematic outlay of
the application of the CPF methodology to powders M.sub.jX.sub.p as
defined earlier for two reactants. It is obvious to someone skilled
in the art that some modifications of these process steps would be
done depending on the starting reactants, the desired precursor and
the final desired product.
[0150] The starting raw materials for this process are chosen from
Groups IA, IIA, IIIA, IVA and transition metals with the anion
being monatomic or a polyanion selected from Groups IIIA, IVA, VA,
VIA and VIIA. The final powders are cation compounds of anions or
polyanions such that the formula is M.sub.jX.sub.p where M.sub.j
may be a single cation or a mixture of metal cations and X.sub.p
may be a single anion, a single polyanion or a mixture of mixed
anions and polyanions. M.sub.j may be M.sub.1 M.sub.2 M.sub.3 or
more which are in stoichiometric or non-stoichiometric ratios and
one or two may be small dopant amounts not more than 10 weight % of
the final powder. The anion and polyanions may be oxides,
carbonates, silicates, phosphates, borates, aluminates,
silicophosphates, stannates, hydroxides, nitrates, oxycarbonates,
hydroxycarbonates, fluorides, oxyfluorides without limited thereto.
Examples of these desired high performance powders are utilized in
lithium ion battery applications, rechargeable batteries, bone
implants, dental implants, structural ceramics, optical
communication fibers, medical patches for drug delivery and
specialized composites of metal-metal, metal-ceramic,
glass-ceramic, glass-metal and others but not limited to these. The
following discussion will illustrate the complexometric precursor
formulation technology as applied to the synthesis of a lithium
cathode material for lithium ion batteries. It is known that this
art is not limited to this illustrative example but is applicable
to numerous specialized high performance powders which are very
expensive to manufacture today. The reactants in each solution are
preferably no more than 30 wt. % of the solution.
[0151] A first reactant solution A is prepared by dissolving the
solid in a selected solvent, preferably a polar solvent such as
water but not limited thereto. It is understood that the choice of
solvent depends on the type of final powder product desired, the
formulated composition of the final powder and the physical
characteristics required for achieving the performance of the final
powder. The choice of the solvent is determined by the solubility
of the solid reactant A in the solvent and the temperature of
dissolution. It is preferred to dissolve at ambient temperature and
to dissolve at a fast rate so that solubilization is not energy
intensive. The dissolution may be carried out at a slightly higher
temperature but preferably below 100.degree. C. Only if other
dissolution methods fail should a higher temperature be used. Other
dissolution aids may be addition of an acid or a base. The solution
concentration is preferably low as this influences concentration at
the surface bubble interphase during the nucleation which
determines the final powder size. It is important to select the
proper chemical environment in order to produce the right
nucleation to yield the desired final powder characteristics.
[0152] The cost of the starting materials should also be considered
in the sum total of the process cost. Generally, lower cost raw
materials are the salts of chlorides, nitrates, hydroxides and
carbonates. Acetate salts and other compounds are usually prepared
from these so these downstream compounds will be at higher cost.
Nitrates and sulfates are readily soluble in water but they also
release noxius gases during high temperature calcination. The
purity of the starting materials is also a cost consideration and
technical grade materials should be the first choice and additional
inexpensive purification should be factored in the selection of the
starting materials.
[0153] A second reactant solution B is also prepared in the same
way as reactant solution A. The solid starting material and the
solvent selected for dissolution should yield the fastest
dissolution under mild conditions as possible.
[0154] The reactor, 1, set-up for both solutions A and B is
diagrammed in FIG. 4. Baffles, 2, are preferred and are preferably
spaced at equal distance from each other. These baffles promote
more efficient mixing and prevent build-up of solid slags on the
walls of the reactor. A top cover, 5, is latched to the bottom
section of the vessel using a flange or bolts, 4. An O-ring, 3,
serves to seal the top and bottom sections of the reactor. The
mixer shaft, 7, and the propeller, 8-9, are shown in FIG. 4 and in
more detail in FIG. 5. The mixer shaft is preferably in the center
of the reactor vessel and held in place with an adaptor or sleeve,
6. Gas is introduced through a gas diffuser such as gas tubes, 10,
which have small outlets on the tube for exit of the gas. These gas
tubes are placed vertically into the reactor through the portholes
of the top cover and held in place with adaptors, 6. The gas used
for bubbling is preferably air unless the reactant solutions are
air-sensitive. In this instance, inert gas is employed such as
argon, nitrogen and the like. Carbon dioxide is also used if a
reducing atmosphere is required and it can also be used as a
dissolution agent or as a pH adjusting agent. Ammonia may also be
introduced as a gas if this is preferable to use of an ammonia
solution. Ammonia can form ammonia complexes with transition metals
and a way to dissolve such solids. Other gases such as SF.sub.6,
HF, HCl, NH.sub.3, methane, ethane or propane may also be used.
Mixtures of gases may be employed such as 10% O.sub.2 in argon as
an example. Another porthole on the top cover of the reactor is for
the transfer tube (not shown) and another porthole can be used for
extracting samples, adding other reactant, as Reactant C for pH
adjustment or other, and also or measurements of pH or other needed
measurements.
[0155] The agitator blade illustrated in FIG. 5 with a concentric
wire design is preferred over the regular paddle type since this
assists in bubble formation and allows the solution system to be in
a dynamic motion such that fresh bubble surfaces are continuously
and rapidly produced as the second solution of reactant B is being
transferred into the reactor containing solution of reactant A. The
agitator blade has concentric wire wound, 9, and it can rotate on
its axis, 10, as shown in a top view in FIG. 5A. A side view of
this design is shown in FIG. 5B. FIGS. 5C-5G illustrate different
arrangements of blades. The concentrically wound wires are not
shown to simplify the diagrams. The blade is attached to the mixer
shaft (7) as shown in FIG. 5C and one set of propellers with three
blades rotate horizontally on their own axes (FIG. 5C-10) and also
rotate vertically (FIG. 5C-11) simultaneously on the mixer shaft
axis, 11. In FIG. 5D, two sets of propellers with three blades each
are drawn which move as in FIG. 5C. There are three blades arranged
alternately on the mixer shaft in FIG. 5E. In FIG. 5F, the
arrangement is similar to FIG. 5C but there are two sets of
propellers with four blades. In FIG. 5G, the four blades are
arranged one above the other on the mixer shaft as in FIG. 5C.
There can be many variations of these configurations with different
number of blades, different blade dimensions, different plurality
of blades in a set, several sets of blades, different angular
orientation relative to each other, different number of coils per
blade, etc. The blade configurations are not limited to these
illustrations in FIG. 5.
[0156] The rate of transfer has a kinetic effect on the rate of
nucleation. A preferred method is to have a fine transfer stream to
control the concentration of the reactants at the bubble surface
interface which influences the complexcelle formation and the rate
of nucleation over the rate of crystal growth. For smaller size
powder, a slower transfer rate will yield finer powders. The right
conditions of the competing nucleation and growth must be
determined by the final powder characteristics desired. The
temperature of reaction is preferably ambient or under mild
temperatures if needed.
[0157] Upon completion of the reaction of reactant A and reactant
B, the resulting slurry mixture containing the intermediate
complexcelle is dried to remove the solvent and to obtain the dried
powder. Any type of drying method and equipment can be used and
such drying is preferably at less than 350.degree. C. Drying can be
done using an evaporator such that the slurry mixture is placed in
a tray and the solvent is released as the temperature is increased.
Any evaporator in industrial use can be employed. The preferred
method of drying is by using a spray dryer with a fluidized nozzle
or a rotary atomizer. These nozzles should be the smallest size
diameter although the size of the powder in the slurry mixture has
already been predetermined by the reaction conditions. The drying
medium is preferably air unless the product is air-sensitive. The
spray dryer column should also be designed such that the desired
moisture content is obtained in the sprayed particulates and are
easily separated and collected.
[0158] The spray dried particles obtained by the CPF methodology
are very fine and nanosize. Definitive microstructures or
nanostructures by the CPF process are already formed during the
mixing step. Novel microstructures or nanostructures looking like
flowers or special layering such that these structures are called
nanorose, nanohydrangea, or nanocroissant or other description
depending on the formulation of the powder. Such structures also
translate to the final powder after the calcination step.
[0159] After spray drying, the powder is transferred to a calciner.
No crushing or milling is required since the spray dried powders
are very fine. In large scale production, this transfer may be
continuous or batch. A modification of the spray dryer collector
such that an outlet valve opens and closes as the spray powder is
transferred to the calciner can be implemented. Batchwise, the
spray dried powder in the collector can be transferred into trays
or saggers and moved into a calciner like a box furnace although
protection from powder dust should also be implemented. A rotary
calciner is also another way of firing the powder. A fluidized bed
calciner is also another way of higher temperature heat treatment
of the spray dried powder. The calcination temperature is
determined by the composition of the powder and the final phase
purity desired. For most oxide type powders, the calcination
temperatures range from as low as 400.degree. C. to slightly higher
than 1000.degree. C. After calcination, the powders are crushed as
these are soft and not sintered. The CPF process delivers
non-sintered material that does not require long milling times nor
does the final CPF process require classifiers to obtain narrow
particle size distribution. The particle sizes achievable by the
CPF methodology are of nanosize primary and secondary particles and
up to small micron size secondary particles ranging to less than 50
micron aggregates which are very easily crushed to smaller size. It
should be known that the composition of the final powder influences
the morphology as well.
[0160] A brief stepwise summary of the CPF methodology is given
below.
[0161] A first solution or slurry solution of M=M.sub.1 chosen from
the metal chlorides, metal nitrates, metal hydroxides, metal
acetates, metal carbonates, metal hydrocarbonates, metal hydroxyl
phosphates and metal hydroxysilicates but not limited to these
would be prepared. The purity of the starting reactant for M.sub.1
should be defined by the final purity desired and the degree of
purification that may be done in a preliminary step.
[0162] A second solution or slurry solution of M=M.sub.2 also
chosen from the same metal salts as for the first solution. The
purity of the starting reactant for M.sub.2 should also be chosen
on the basis of the final purity of the final product and the
degree of purification needed in a preliminary step.
[0163] The solvent in both the first and second solution is
preferably deionized water at acidic or basic pH and ambient
temperature. An acid or a base may be added to the first or second
solution to aid in solubilizing the reactants and/or the
temperature may be increased but preferably not more than
100.degree. C., and/or the solubilizing mixing rate be more
vigorous and solubilizing time increased. If conditions require
more adverse temperature and time, then the process may proceed as
slurry solutions. Other solvents to dissolve the starting materials
may also be used if water is insufficient for dissolution. Such
solvents may be polar solvents as alcohols or non-polar solvents
typically used in general organic preparations. It is important to
consider raw material costs during the evaluation of the process so
that production cost does not decrease the value-added performance
advantages of the CPF powder.
[0164] A CPF reactor designed or configured so that gas may be
introduced into the vessel is charged with the first solution. The
gas may be air, argon, carbon dioxide, nitrogen, or mixtures of
these preferably of normal purity. The gas may be inert for
reactions that are adverse in air. Likewise, the gas may also be a
possible reactant such as, for example, those reactions wherein
carbon dioxide is utilized to produce carbonates or bicarbonates,
or hydroxycarbonates and oxycarbonates but not limited to
these.
[0165] The gas may be introduced by a gas diffuser such as gas
tubes having holes in the tube from which the gas introduced from
the inlet exits into the reactor vessel creating a vigorous flow
and a bubbling solution with numerous fine micro-bubbles. The holes
may be sized to insure bubbles are generated over the entire length
of the tube.
[0166] The gas may also be introduced by mechanical gas diffusers
with pumps that may circulate both gas and solution which also
improves mixing of the solutions.
[0167] The gas flow rate, in conjunction with the mixing speed of
the agitator, should be enough to create suspended micro bubbles
such as a foamy solution.
[0168] An agitator blade is configured to produce vigorous mixing
to produce a frothy slurry solution or frothy solution. The
agitator blade may be a concentric loop to promote incorporation of
the gas and the formation of fine bubbles. The concentric loop may
rotate horizontally and vertically. In addition, the agitator blade
may be dual, triple, quadruple, quintuple or other configuration
and not limited to these. Depending on the height of the reactor
vessel, several agitator blades may be used.
[0169] The mixing speed should be fast enough to maintain bubbles
of first solution such that the second solution being added drops
into the bubbles of the first solution creating a micro or nano
contact onto the surface of the bubbles of the second solution.
[0170] The first solution may be added to the second solution. The
resulting product performance may be different depending on the
method of addition.
[0171] The mixing temperature is preferably ambient or slightly
elevated but not more than 100.degree. C.
[0172] The resulting mixture of first and second solutions may be a
solution or a slurry mixture.
[0173] The resulting reaction product is dried by any drying method
using known industrial equipment including spray dryers, tray
dryers, freeze dryers and the like, chosen depending on the final
product preferred. The drying temperatures would be defined and
limited by the equipment utilized. The desired drying temperatures
are usually from 200-325.degree. C.
[0174] The resulting mixture is continuously agitated as it is
pumped into the spray dryer head if spray dryers, freeze dryers or
the like are used. For tray dryers, the liquid evaporates from the
surface of the solution.
[0175] The dried powders are transferred into the next heating
system batch-wise or by means of a conveyor belt. The second
heating system may be a box furnace utilizing ceramic trays or
saggers as containers, a rotary calciner, a fluidized bed, which
may be co-current or counter-current, a rotary tube furnace and
other similar equipment but not limited to these. The calcination
temperature depends on the final product requirements and could be
as high as 1000.degree. C. and up to as much as 3000.degree. C. or
more as in the case of glassy silicates.
[0176] The heating rate and cooling rate during calcinations depend
on the type of final product desired. Generally, a heating rate of
about 10.degree. C. per minute is preferred but the usual
industrial heating rates are also applicable.
[0177] Calcining may also require inert gases as in the case of
those materials that are sensitive to oxidation. As such, a
positive flow of the inert gas may be introduced into the calcining
equipment.
[0178] The final powder obtained after the calcining step is a
fine, ultrafine or nanosize powder that does not require additional
grinding or milling as is currently done in conventional
processing. Particles are relatively soft and not sintered as in
conventional processing.
[0179] The final powder is preferably characterized for surface
area, particle size by electron microscopy, porosity, chemical
analyses of the elements and also the performance tests required by
the preferred specialized application.
[0180] The CPF methodology for the production of fine, ultrafine
and nanosize powders offers several advantages. One of the
improvements is reduction in the number of processing steps. There
is no significant milling and firing sequence in the CPF method.
The total production time for this CPF methodology route to fine,
ultrafine and nanosize powders is less than or equal to 25% of
current conventional processing technologies for such similar
powders. Final powder production cost using CPF methodology can be
significantly reduced by as much as 75-80% of current conventional
processing. Performance improvements of these powders produced by
CPF are at least 15% or more than those traditional ceramic powders
currently produced by presently known technologies. The CPF process
can be utilized for the preparation of different types of powders
and is not limited to a group of powder formulations.
[0181] This CPF process can be applied to make the desired powder
for the lithium ion batteries, such as lithium cobalt oxide,
lithium nickel oxide, lithium manganese oxide and the doped lithium
metal oxides of this type, the mixed lithium metal oxides of said
metals and the doped derivatives, lithium iron phosphate and the
doped lithium iron phosphates as well as other lithium metal
phosphates, lithium titanates and other materials for the storage
batteries. The CPF process can be applied to produce medical
powders such as the specialized calcium phosphates for medical
applications like bone implants. The CPF process can also be used
for the preparation of other advanced ceramic powders such as
lithium niobates and lithium tantalates, lithium silicates, lithium
aluminosilicates, lithium silicophosphates and the like.
Semiconductor materials can also be prepared by the CPF process as
well as specialized pharmaceutical drugs. High surface area
catalysts can be made by the CPF process and such catalysts would
have higher catalytic activity as a result of a finer particle
size, higher surface area and higher porosity made possible by the
CPF methodology. Specialized coatings requiring nanosize powders
can be economically prepared by the CPF method. This CPF process
can also be used for the preparation of non-lithium based
materials. The versatility of this methodology allows itself to be
easily modified in order to achieve the customized, tailored powder
needed. Furthermore, this methodology is easily adapted for large
scale industrial production of specialized powders requiring a
narrow particle size distribution and definitive microstructures or
nanostructures within the fine, ultrafine or nanosize powders.
Having a cost effective industrial scale powder for these
specialized applications will allow commercial development of other
devices otherwise too costly to manufacture.
[0182] The complexometric precursor formulation methodology or CPF,
creates a fine, ultrafine or nanosize powders via the formation of
a complexcelle of all the ions of the desired powder composition on
a bubble surface interface. CPF has many advantages over known
prior art.
[0183] Only the main reactants for the chemical formula of the
compound to be synthesized are used. This will reduce the cost of
the raw materials. The starting raw materials can be low cost.
Technical grade materials can be used and if needed, purification
can be done in-situ.
[0184] Total processing time is significantly less, about 1/5 to
1/2 of the processing times for the present industrial
processes.
[0185] Special nanostructures are preformed from the complexcelle
which are carried over to the final product thus enhancing the
performance of the material in the desired application. For the
purposes of the present invention nanostructures are defined as
structures having an average size of 100 to 300 nm primary
particles.
[0186] Neither surfactants nor emulsifiers are used. The initiation
reaction occurs at the surface of the bubble interface. In fact, it
is preferable that surfactants and emulsifiers are not used since
they may inhibit drying.
[0187] Size control can be done by the size of the bubbles,
concentration of the solutions, flow rate of the gas, transfer rate
of second reactant into the first reactant.
[0188] No repetitive and cumbersome milling and classification
steps are used.
[0189] Reduced calcination time can be achieved and repetitive
calcinations are typically not required.
[0190] Reaction temperature is ambient. If need for solubilization,
temperature is increased but preferably not more than 100.degree.
C.
[0191] Tailored physical properties of the powder such as surface
area, porosity, tap density, and particle size can be carefully
controlled by selecting the reaction conditions and the starting
materials.
[0192] The process is easily scalable for large scale manufacturing
using presently available equipment and/or innovations of the
present industrial equipment.
EXAMPLES
Preparation of Coin Cells
[0193] The standard practice for coin cell testing has been used in
all example and is described herein for reference. The material was
made into electrodes in the same way and tested in an Arbin battery
cycler (BT-2000) under the same cycling conditions of voltage and
current. As such, side-by-side comparison of the battery cycling
performances definitively exemplifies the advantages of the CPF
methodology over current industrial production processes.
[0194] Electrodes were prepared by mixing 80 wt. % of active
material, 10 wt. % of carbon black, and 10 wt. % PVDF
(polyvinylideneflouride) in NMP (1-methyl-2-pyrrolidone). The
resulting slurry was cast on aluminum foil and dried in a vacuum
oven at 115.degree. C. for 24 h. CR2032-type coin cells were
fabricated in an argon-filled glove box using lithium metal as the
counter electrode. The cathode weight was around 4 mg per
electrode. The electrolyte was a 1 M solution of LiPF.sub.6
(lithium hexafluorophosphate) in a 1:1:1 volume mixture of
EC:DMC:DEC (ethylene carbonate, dimethyl carbonate, and diethyl
carbonate). The separator (Celgard 2400) was soaked in the
electrolyte for 24 h prior to battery testing. Coin-cells were
galvanostatically charged/discharged on the Arbin battery cycler at
the stipulated current densities. Tests were done at ambient
temperature. Both comparative example and the example coin cells
were done at the same time under the same conditions.
Battery Cycle Data
[0195] The batteries were tested with cycles 1-5 measured for a
2.5-4.8V cut off voltage @C/10.; for Cycles 6-10 based on a
2.5-4.6V cut off voltage @C/3 and for cycles 11-1000 at 2.5-4.6V
cut off voltage @1 C.
EXAMPLES
Comparative Example 1
[0196] Commercially available lithium cobalt oxide powder was
obtained from Sigma Aldrich and characterized by field emission SEM
(FIGS. 8 A and 8B) and XRD (FIG. 9) as well as by coin cell
testing.
[0197] The scanning electron micrograph of this commercial
LiCoO.sub.2 in FIG. 8A has a magnification of 2000.times. and was
taken as received. A second micrograph in FIG. 8B has a
magnification of 25000.times.. In FIG. 8A, the particles are
acicular and have several large agglomerates more than 10 microns
that fused together during the calcination stage. On higher
magnification, layers of the particles are noted for some particles
that were not fused but it is also shown that there are smooth
areas from fusion of particles. This is often found in solid state
processes which are a calcination of blended mixed solids of the
reactants that combine by sintering at high temperature. It is
expected that the particles so derived would be large in size and
will need to be milled and classified to obtain the size
distribution preferred.
[0198] The X-ray powder diffraction in FIG. 9 shows a single phase
crystalline LiCoO.sub.2.
[0199] The capacity of this lithium cobalt oxide prepared
commercially is shown in FIG. 14 together with Example 2 prepared
by CPF.
Example 2
[0200] Lithium cobalt oxide was prepared using a reactor vessel as
shown in FIG. 4 with a mixer having an agitator blade as shown in
FIG. 5. In one reactor, a weighed amount of lithium carbonate (46.2
grams, 99% purity) was added to the reactor containing one liter of
deionized water. Carbon dioxide gas was allowed to flow through the
reactor using a gas tube bubbler on the side or a diffuser bubbler
at the bottom of the vessel. A second reactor also equipped with a
tube bubbler or a diffuser bubbler contained a weighed amount of
cobalt carbonate (120.2 grams, 99% purity) and one liter of
deionized water. Carbon dioxide gas was allowed to flow through the
bubblers. Ammonia, 250 mL, was added to the second reactor. After a
given amount of time to allow dissolution or vigorous mixing of the
corresponding reactants, the cobalt solution was pumped into the
lithium solution at a rate of at least 1 L/h. Reaction temperature
was ambient and gas flow maintained a sufficient amount of bubbles.
The resulting mixture was passed through a spray dryer. The outlet
temperature was 115.degree. C. The dried powder was collected and
placed in a sagger and fired in a box furnace in air for 5 h at
900.degree. C. Scanning electron micrographs (FIGS. 10-12) and
X-ray powder diffraction patterns (FIG. 13) were taken of the dried
powder and the fired powder.
[0201] The slurry after mixing the reactants was placed on a glass
surface to dry in air. The air-dried powder was analyzed by field
emission SEM and the micrograph is shown in FIG. 10. It is shown
that there is some nanostructure already formed from the CPF
methodology. The particles appear to align as staggered layers.
Primary particles are in the nanometer range as shown by several
individual particles interspersed within.
[0202] In FIG. 11A (10000.times.) and 11B (25000.times.), the same
nanostructure can be seen after spray drying the slurry mixture
from the mixing step. The layering structure is very clearly shown
in FIG. 11B. That the nanostructure still remains after drying
indicates that this formation is an advantage of the CPF
process.
[0203] After the calcination step for 5 h at 900.degree. C., the
layered nanostructure observed in FIGS. 10 and 11 still remains
intact in the calcined powder as shown in the SEM micrograph in
FIG. 12 at 10000.times. which consists of loosely bound layers of
the particles allowing ease of Li migration within the structure
during battery cycling. Such flaky structure resembles a
"nanocroissant" and has already been formed from the precursor feed
to the spray dryer and thereon to the calciner.
[0204] Coin cells were prepared as described in the preparation of
coin cells. The capacity of this lithium cobalt oxide prepared by
the CPF methodology is shown in FIG. 14 plotted with the commercial
sample in Example 1 for 500 cycles at C/20. From the data, the
commercial sample of Example 1 performed lower, as shown by the
lower discharge capacity. Both powders decreased in capacity with
increase in the number of cycles. However, the powder prepared by
the CPF process exhibited higher capacity up to 400 cycles compared
to the commercial sample of Example 1. At 300 cycles, the capacity
of the CPF powder of Example 2 was 110 mAh/g compared against the
capacity of the commercial sample at 300 cycles which was 80
mAh/g.
Example 3
[0205] The powders in Examples 1 and 2 were refired at 900.degree.
C. for another 5 h. Coin cells were prepared as described. A
comparison of the battery cycling tests is given in FIG. 15 at 1 C
for 500 cycles.
[0206] In the battery cycling tests at a higher C rate of 1 C, the
lithium cobalt oxide powder from Example 2 that was refired again
performed significantly better than the commercial powder that was
also refired at the same temperature and for the same time period.
The capacity of the commercial sample dropped from 120 mAh/g to 20
mAh/g after 200 cycles. The CPF sample had a capacity of 100 mAh/g
after 300 cycles and 80 mAh/g at 400 cycles.
[0207] The present invention provides a cathode for a battery
wherein the battery has a capacity of at least 80 mAh/g after 200
cycles
[0208] The scanning electron micrographs of the refired samples are
shown in FIGS. 16 and 17 at the same magnification of 10000.times.
for comparison. While recalcination for another 5 h has caused more
fusion in both samples, it is noted that the commercial sample of
lithium cobalt oxide has larger fused particles and the layers were
also more fused together. The lithium cobalt sample prepared by
this invention still retained much of the layered structure and the
additional firing has not diminished battery performance
significantly compared to the commercial sample.
Example 4
[0209] The same procedure described in Example 2 was used in this
example but with the added nickel and manganese compounds to
illustrate the synthesis of multicomponent lithium oxides by the
CPF methodology. The formulation made is
Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2 which is a high
energy lithium nickel manganese cobalt oxide material for lithium
ion batteries that would meet the electric vehicle performance
standards.
[0210] Nickel hydroxide (16.8 grams, 99%) and cobalt carbonate
(14.4 grams, 99.5%) were weighed out and placed in a reactor vessel
described in FIG. 4 equipped with a tube bubbler and an agitator as
shown in FIG. 5 already containing one liter of deionized water and
140 mL of acetic acid (99.7%). The solids were mixed at ambient
temperature to obtain a solution of both metals. Manganese acetate
(123.3 grams) was then weighed out and added to the same reactor. A
similar reactor was also set-up to contain one liter of deionized
water and lithium carbonate (44.7 grams, 99%). Carbon dioxide was
bubbled through the gas bubbler. Ammonia, 100 mL, was added to the
Li-containing reactor. The Co, Ni, Mn solution was then pumped into
the Li-containing reactor at about 3.5 L/h at ambient temperature.
Additional ammonia, 155 mL, was then added to the mixture to
maintain pH of at least 9.0. The resulting mixture was then dried
in a spray dryer. Inlet temperature was at 115.degree. C. The
Li--Co--Ni--Mn spray dried powder was then placed in a sagger and
calcined at 900.degree. C. for 5 h. The fired powder was very soft
and was just crushed. No classification was done.
[0211] Scanning electron micrographs (FIGS. 18-20) and X-ray powder
diffraction patterns (FIG. 21) were taken of the dried powder and
the fired powder. Note that the SEM data in FIGS. 18A (2000.times.)
and 18B (10000.times.) before spray drying and FIGS. 19A
(5000.times.) and 19B (10000.times.) after spray drying show a
"nanorose" or a "nanohydrangea" structure as the nanostructures
formed by the layering of the particles look similar to these
flowers. The particles form nanostructure layers at the mixing
stage where the complexcelle nucleation begins and this same
nanostructure is retained even after spray-drying. The calcined
powder has discrete nanoparticles about 200-300 nm and some very
loose agglomerates as shown in the SEM micrographs in FIGS. 20A
(10000.times.) and 20B (25000.times.).
[0212] A crystalline lithium nickel manganese cobalt oxide was
obtained in the X-ray powder diffraction pattern in FIG. 21.
[0213] Coin cells were prepared as described in Example 1. The
capacity of this lithium nickel cobalt manganese oxide prepared by
the CPF methodology is shown in FIGS. 22-24.
[0214] In FIG. 22, the capacity of this lithium nickel manganese
oxide was relatively constant at an average of 125 mAh/g for 500
cycles at a high C rate of 1 C. This is indicative of potential
high performance in lithium ion batteries for electric vehicle
applications. Capacity retention for as much as 500 cycles at 1 C
is excellent performance.
[0215] In FIG. 23A, the battery performance for the same material
was done in a temperature controlled chamber at 30.degree. C. and
plotted showing different cycling rates from C/20 to 1 C. As shown,
the capacity decreases as the C rate increases. At C/20, the
capacity was about 250 mAh/g and at 1 C, about 150 mAh/g.
[0216] In FIG. 23B, the C rates shown are C/10, C/3 and 1 C for 5
cycles each. Capacities were 240 mAh/g, 180 mAh/g and 150 mAh/g,
respectively. The battery cycling tests were done at 30.degree. C.
in a temperature controlled chamber.
[0217] In FIG. 24A, the battery coin cells were placed in the
temperature controlled chamber at 25.degree. C. Cycling rates were
taken from C/20 to 1 C. The capacity at C/20 was almost 300 mAh/g.
At 1 C, the capacity was at 180 mAh/g. This is attributed to a
better controlled environment. The cycling data at 1 C for 500
cycles is shown in FIG. 24B. Capacity was constant for 500 cycles
at 1 C rate at 25.degree. C.
Example 5
[0218] A cathode material, LMPO.sub.4, such as LiFePO.sub.4, which
is also preferably coated with carbon to promote conductivity and
may be doped or not, can be made by this CPF methodology. The iron
source can be selected from divalent salts of iron. The phosphate
source can be H.sub.3PO.sub.4, ammonium phosphates, ammonium
dihydrogen phosphates and the like. Iron is either a +2 or a +3
ion. The Fe.sup.+2 salt is preferred over the Fe.sup.+3 salt. The
reactions must be done under inert atmosphere to prevent the
oxidation of Fe.sup.+2 to Fe.sup.+3. A reducing atmosphere can also
be used to reduce the Fe.sup.+3 to Fe.sup.+2.
[0219] To illustrate the preparation of LiFePO.sub.4, an iron salt
soluble in aqueous solvents like water is prepared in one reactor.
Such salts can be iron oxalate, iron nitrate and others. Carbon
dioxide gas can be introduced in the solution. Phosphoric acid is
also added to the solution. In a second reactor, a lithium salt
such as lithium carbonate, lithium hydroxide and the like is
dissolved in water under carbon dioxide gas. The iron phosphate
solution in reactor 1 is then slowly transferred into the lithium
solution in the second reactor. Ammonia solution may be introduced
simultaneously as the iron solution or at the end of the transfer
of the iron solution. The slurry solution is then dried using a
spray dryer and the spray dried powder is calcined under inert
atmosphere to obtain LiFePO.sub.4. If a dopant is added from
selected metals, this dopant solution must be dissolved in any
reactor. The carbon coating can be attained by adding a carbon
material to obtain not more than a 10 wt. % carbon in the product.
The coating may comprise alkali or alkaline earth metals, Group III
A and IV A and transition metals or an organic or another inorganic
compound.
[0220] The compound M.sub.j; prepared by the complexometric
precursor formulation methodology of claim 14 wherein said coating
comprises carbon or a carbon-containing compound
[0221] Other types of phosphate compounds such as calcium phosphate
may be made in a similar way to obtain a calcium phosphate
nanopowder that can be used for bone implants and other medical
applications as well as dental applications.
Example 6
[0222] Lithium cobalt oxide was prepared using a reactor vessel as
in FIG. 4 with agitator blades as in FIG. 5. Cobalt nitrate
hexahydrate, 149.71 grams, was weighed into the reactor containing
one liter of deionized water. Air was bubbled through the solution
using fritted gas tubes. Lithium hydroxide monohydrate, 25.86
grams, was dissolved in deionized water, 1 L, in a second container
then transferred into the cobalt solution. Ammonia (28%), 125 mL,
was added to the mixture. The mixture was spray dried and calcined
at 900.degree. C. for 5 h.
[0223] The SEM micrographs in FIGS. 25 and 26 show the particle
size transitions for the spray dried material to the fired product
at 10000.times.. Primary particles are about 200-300 nm and
secondary ones are about 3.5 microns. The particles are nanosize to
ultrafine size. There is no significant sintering observed from
micrographs taken after the calcination step. No classification was
done after the calcination step; the fired powder was lightly
crushed.
[0224] The X-ray powder diffraction pattern in FIG. 27 show a
crystalline lithium cobalt oxide phase.
[0225] The coin cell tests in FIG. 28 show a discharge capacity of
about 150 mAh/g with slight decrease after 50 cycles at ambient
temperature at 0.05 C rate.
Example 7
[0226] Example 2 was repeated. Lithium carbonate (46.6 grams) was
weighed and dissolved in 1 L of deionized water under CO.sub.2 gas
at ambient temperature. In another vessel with a liter of deionized
water and CO.sub.2, 120.6 grams of cobalt carbonate was weighed and
250 mL of ammonium hydroxide was also added. The second mixture was
transferred into the lithium solution in about one hour, spray
dried (inlet temperature of 220.degree. C.) then calcined for 5 h
at 900.degree. C.
[0227] The X-ray powder diffraction pattern in FIG. 29 is a
crystalline lithium cobalt oxide.
[0228] Particle size of the calcined powder was done by FESEM
(field emission scanning electron microscopy) in FIGS. 30 A-C.
[0229] Coin cell test data is given in FIG. 31 for Example 7 and
the commercial sample (Sigma Aldrich) done at room temperature for
500 cycles at 1 C. The product prepared by the CPF process is
showed a capacity of 100 mAh/g at 400 cycles while the commercial
sample had a capacity of about 70 mAh/g.
Example 8
[0230] The calcined product in Example 7 was fired again for
another 5 h at 900.degree. C. The X-ray powder diffraction pattern
is given in FIG. 32 which is a single phase crystalline lithium
cobalt oxide.
[0231] The refired LiCoO2 had particle sizes similar to Example 7
which is a single fire at 5 h at 900.degree. C. The SEM photos in
FIG. 33 are at magnifications 5000.times., 10000 x, and
25000.times..
[0232] A comparison of Example 8 against the refired commercial
sample in Example 3 is shown in FIG. 34. The battery performance
after 250 cycles dropped to 30 mAh/g capacity for the commercial
sample but Example 8 exhibited 120 mAh/g at 250 cycles and was 100
mAh/g after 500 cycles. The coin cell conditions were RT at 1 C.
These results indicate superior advantage of the complexcelle
formation of the CPF synthetic method over a similar product
prepared by traditional methods.
Example 9
[0233] The reactants in Example 7 can be prepared in the same
manner. Another compound such as aluminum oxide or aluminum
fluoride can be added to the second solution already containing
cobalt as a dopant. The amount of this dopant compound depends on
the preferred dopant concentration for enhanced performance but is
usually less than 10% by weight of the total composition. In some
cases, more than one dopant is added depending on the desired
improvement in performance in the presence of the dopant. One of
these is improvement in battery cycling results such as longer
cycle life and higher stable capacity.
[0234] Dopant starting materials are usually salts of oxides,
hydroxides, carbonates favorably over the nitrates, sulfates,
acetates and the like. Among those already used by other
researchers are alkaline metals and transition metals such as Al,
Ti, Zr, Mg, Ca, Sr, Ba, Mg, Cr, Ga, B and others but not limited to
these. A general formula for doped lithium cobalt oxide would be
LiCo.sub.1-pD.sub.pO.sub.2.
Example 10
[0235] The CPF process can also be used to make other lithium metal
oxides of formula LiMO.sub.2 such as LiMn.sub.2O.sub.4,
LiNiO.sub.2, and other formulations of Example 2, as well as the
doped derivatives and coated derivatives of the formula
LiM.sub.1-pD.sub.pO.sub.2.
[0236] The anion may also be a polyanion such as oxyfluorides and
others. These formulations will be then be variants of
LiM.sub.1-pD.sub.pO.sub.2-xF.sub.x and the like.
[0237] Starting materials for these would be chosen from their
corresponding salts, preferably oxides, carbonates, hydroxides,
nitrates, acetates and others that can be dissolved preferably
under mild conditions of time, temperature and pressure, rendering
easily scale-up to industrial production.
Example 11
[0238] A Li.sub.1.20Ni.sub.0.16Mn.sub.0.53Co.sub.0.11O.sub.2 was
prepared in the same manner as Example 4. Stoichiometric molar
amounts of nickel hydroxide and cobalt carbonate according to the
formula were weighed and dissolved in 1 L of deionized water and
160 mL of acetic acid. Manganese acetate was weighed according to
stoichiometry and dissolved in the nickel-cobalt solution. The
lithium solution was prepared from lithium carbonate under CO.sub.2
and 1 L of deionized water. Ammonium hydroxide was added in the
lithium solution, gas was changed to nitrogen, and the transition
metal containing solution was transferred into the lithium solution
in about 30 minutes. The mixture was dried using a spray dryer. The
SEM micrograph in FIG. 35 for the spray dried powder shows a unique
"nanorose" or nanohydrangea" structure at 20000.times.
magnification.
[0239] The dried powder was then calcined at 900.degree. C. for 5
h. It was then recalcined for another 5 h at the same temperature
and for a third consecutive time for another 5 h. The SEM
micrographs for each firing are in FIGS. 36 A-C at 20000.times. for
better comparison. As observed, the particles are less than one
micron and average about 200-300 nm for all three firing steps, 5 h
to 15h of calcination time. FIG. 37 is a TEM micrograph of the
powder fired three times and the nanosize particles are
evident.
[0240] The X-ray powder diffraction patterns for the first and
second calcinations are given in FIGS. 38A and 38B, respectively.
The additional firing step had the same crystalline pattern as the
first firing step. The battery cycling data in FIGS. 39A and 39B
also show this similarity. A stable capacity of about 110 mAh/g and
120 mAh/g was obtained for 500 cycles for the first and second
calcinations. The cycling profile was C/10 for the first 5 cycles,
C/3 for cycles 6-10, and then 1 C from 11-500 cycles. The tests
were done at room temperature and the small incremental temperature
changes are reflected in the cycling curves varying with these
temperature variations.
[0241] The X-ray powder diffraction pattern for the third firing
step is given in FIG. 40 which is similar to the earlier two firing
steps. The battery cycling data is in FIG. 41 which was done under
the same cycling conditions but extended for 1000 cycles at 1 C
rate. After 1000 cycles, the capacity was around 120-130 mAh/g, an
indication that this powder retained its performance even after
being calcined three times.
[0242] The powder prepared by the CPF process shows very stable
results for all three successive calcination steps and under the
high C rate conditions, excellent cycle life up to 1000 cycles was
obtained, indicative of high battery performance for specialized
applications as the electric vehicle batteries. The CPF method can
also easily produce these powders in larger scale production.
Example 12
[0243] In this example, another lithium mixed metal oxide with a
formulation variant was prepared. It is an objective to determine
the properties of compounds of the formula
Li.sub.1+xNi.sub..alpha.Mn.sub..beta.Co.sub..gamma.O.sub.2.
Manganese is environmentally more acceptable than nickel or cobalt
and is also an inexpensive starting raw material but nickel and
cobalt containing materials outperform manganese materials in
specialized battery applications. The stability of this powder is
critical in order to have longer cycle life. It is also essential
to have excellent capacity at high C rates from 1 C and higher for
at least 500 cycles.
[0244] Starting materials as in Examples 4 and 11 were prepared to
obtain the formulation
Li.sub.1.20Ni.sub.0.17Mn.sub.0.51CO.sub.0.12O.sub.2. The powders
were calcined for 5 h at 900.degree. C. in two successive steps.
These X-ray powder diffraction patterns are in FIGS. 42A and 42B
and similar patterns were obtained. The SEM micrographs in FIGS.
43A and 43B also show very similar particle size distribution and
these were in the nanosize range averaging about 300 nm after 5 h
and 10 h firing steps.
[0245] Coin cell testing results in FIGS. 44A and 44B showed
slightly better performance after 10 h of calcination. For 500
cycles, capacity retentions at 1 C rate were excellent and were
100-110 mAh/g. At the lower C rate, capacities were much higher, up
to about 280 mAh/g at the start at C/10 rate.
Example 13
[0246] The powder in Example 12 was calcined for another 5 h at
900.degree. C. and the crystalline powder is shown in the X-ray
powder diffraction pattern in FIG. 45. The SEM micrograph at
20000.times. magnification still show nanosize average of about 300
nm even after three firing steps. No classification nor milling
were done to achieve this nanosize distribution. The complexometric
precursor formulation methodology is a method for preparing
nanosize powders as demonstrated by these examples. The formation
of the complexcelle enables the formation of fine powders.
[0247] The battery cycling performance of Example 13 is graphed in
FIG. 47 for 1000 cycles at 1 C. At 1000 cycles and 1 C rate, the
capacity was at 130 mAh/g.
Example 14
[0248] A formulation
Li.sub.1.20Ni.sub.0.16Mn.sub.0.52Co.sub.0.12O.sub.2 was prepared
according to the procedures described in Example 4. The spray dried
powder have a flower-like nanostructure similar to "nanohydrangea"
or "nanorose". These are observed in the SEM micrographs at
5000.times., 10000.times., and 20000.times. in FIGS. 48 A-C. Two
calcinations for 5 h at 900.degree. C. produced nanopowders
averaging about 200-300 nm from the spray dried nanostructures as
shown in the SEM micrographs in FIGS. 49A and 49B. The TEM images
in FIG. 50 further show nanosize powders of 200-300 nm.
[0249] The X-ray powder diffraction patterns for the two calcined
powders are given in FIGS. 51A and 51B. A crystalline phase
observed in Examples 4 and 11-13 was noted in Example 14 also for
both firing steps.
[0250] Battery cycling data is given in FIGS. 52A and 52B for the
two firing conditions. A capacity of about 125 mAh/g at 1 C for up
to 500 cycles was obtained in both fired samples. At lower C rate
as C/10, capacity was close to 300 mAh/g.
[0251] These results demonstrate the capability of the CPF process
to produce high performance powders for battery applications. These
powders have excellent cycle life and capacity that meet the
demands for battery applications in the electric vehicle
industry.
Example 15
[0252] Doping and/or coating these lithium mixed metal oxides with
a general formulation Li.sub.1+xM.sub.jX.sub.p where M.sub.j is one
or more transition metal ions and X.sub.p is one or more anions or
polyanions can be done by the CPF process. The dopants would be
selected from a list including Al, Mg, Sr, Ba, Cd, Zn, Ga, B, Zr,
Ti, Ca, Ce, Y, Nb, Cr, Fe, V for example but not limited to these.
The dopant salt can be added to the reactant solution containing
the transition metals and dissolved therein prior to reacting with
the lithium solution. The dopant or coating amounts would be less
than 10 wt % of the total composition. After mixing, the mixture is
preferably spray dried and calcined to the desired temperature and
calcining conditions.
[0253] The invention has been described with reference to the
preferred embodiments without limit thereto. One of skill in the
art would realize additional embodiments and improvements which are
not specifically set forth herein but which are within the scope of
the invention as more specifically set forth in the claims appended
hereto.
* * * * *