Homogeneous nanoparticle core doping of cathode material precursors.
The invention relates to the precipitation of heterogeneous metal bearing material, that
is homogeneously doped with a nanoparticle metal oxide, metal halide, metal anion, or
elemental metal component. The precipitated nanoparticle doped metal bearing
material, especially a hydroxide or oxyhydroxide bearing material, can be used for the
synthesis of cathode materials for secondary batteries.
There are many ways to introduce a dopant element into an existing product. Typical
strategies include coprecipitation, spray drying, physical mixing, and heat treatment.
All of these strategies have drawbacks and some applications are not suitable for
doping with a wide range of dopant elements. Inappropriate impurity elements,
additional processing steps, high firing temperatures, inhomogeneous dopant
distribution, expensive equipment, and availability of starting materials are all
potential problems associated with current technologies.
The preparation of the next generations of cathode materials for use in secondary
batteries often requires the synthesis of a precursor. The precursor can then be fired
with a lithium source to prepare a cathode material. Recent findings have shown that
doping LiNixMnyCozO2 (where x, y, z < 1 and x+y+z = 1) cathode materials with
different elements, including but not limited to Mg, Ti, Zr, Cr, and Al, has yielded
products with improved cycle life, stability, performance, and safety characteristics. It
is therefore important to prepare precursors that can be easily transformed into cathode
materials. It is even more beneficial if the precursors can be easily doped with other
elements and that the precursor can be used to directly prepare the cathode material
without additional processing steps.
A common method to prepare cathode precursor material is precipitation. Using this
method, a suitable metal salt, for instance cobalt sulphate, nitrate, or chloride, is
dissolved in water and precipitated by increasing the pH to yield the metal hydroxide
or oxyhydroxide precursor. Dopants can be introduced through co-precipitation
reactions by preparing feed solutions of the required dopant salt, for example
MgSO4.aq. The Mg salt can be combined with the cobalt feed solution or introduced
separately and the combination of salts is precipitated by adjusting the pH to yield a
magnesium doped cobalt hydroxide or oxyhydroxide. This precipitated material can
contain a homogeneous distribution of Mg atoms in the cobalt hydroxide or
oxyhydroxide precipitate. This method is only applicable if the dopant, for example
Mg +, and the matrix material, for example Co2+ are a) soluble together in the same
solvent and b) precipitate together to give a homogeneous distribution of elements.
For example, doping with Ti is not very straightforward. Simple Ti4+ salts that
dissolve in water are not ubiquitous as aqueous solutions of Ti4+ generally yield
hydrous oxides. TiOSO4 is a mixture of TiO2 and H2SO4 and although a possible
starting material (such as used in JP-2006-147499), this chemical is a highly toxic and
corrosive substance. In addition, the use of TiOSO4 as a reagent introduces sulphate
impurities in the precipitated material. Alkoxides and other organometallic substances
are other possible starting materials, but these are generally expensive and insoluble in
water.
Coprecipitation of a dopant with a major component can also lead to impurity
formation. For example, in the preparation of Ni/Co/Al(OH)2, by precipitation with
base, the use of nickel cobalt and aluminum sulphate salts can lead to the formation of
impurity phases in the nickel cobalt aluminum hydroxide or oxyhydroxide product. In
this system, an Alx(SO4)y(OH)2 impurity can be formed, leading to an increase in
sulphate impurity levels in the final product.
Spray drying can also yield homogeneously doped materials. This method can be
tedious and expensive and the correct conditions must be found to yield particles with
the correct size, morphology, and distribution of elements in the final product. As with
coprecipitation, a suitable soluble metal salt and dopant salt must be found if the spray
drying is performed from dissolved metal solutions. If the reactants are not available
as simple salts, a suitably small, well dispersed precursor metal is needed for spray
drying if the size of the spray dried particles is to be controlled. If the major feed
reactant is a relatively large solid, the material is only coated with a dopant and is not
homogeneously doped through to the core of the spray dried product. Spray drying
can also lead to porous, low density products and this can lead to low density cathode
materials.
To avoid contamination or introduction of impurity elements, spray drying is only
useful if the spray dried material can decompose to yield a suitable final material.
Hence, if Co3O4 is desired, Co(NO3)2, Co(OH)2, or CoCl2 salts and the like are more
desirable since the corresponding spray dried salts can be thermally decomposed
directly to form relatively pure Co3O4. In contrast, the decomposition of CoSO4 would
lead to higher sulphur impurity levels if the counterion does not decompose to form a
labile gas.
Similar challenges to spray drying are encountered with spray pyrolysis. In addition to
the requirements of soluble precursors or fine feed particle materials, expensive
equipment, and fine control of particle size and morphology, the dopant element must
be soluble in the precursor phase to the dopant levels required. For instance, in the
production of spray pyrolysed Mg doped Co3O4, the level of Mg doping can reach an
upper limit, likely due to the solubility and element mobility of dopant atoms in the
Co3O4 crystal structure. In addition, if the mobility of the dopant elements is not
appropriate, Co3O4 with pockets of higher or lower concentrations of elements can be
the result. Co3O4 can also be less reactive than cobalt hydroxides and oxyhydroxides
and would require higher temperatures to react with Li2CO3 in the preparation of
cathode materials.
Another method to produce homogeneously doped materials is to dissolve the
appropriate metal nitrate salts in their respective waters of crystallization to form a sol.
For example, in the preparation of Li(Ni1-xMx)O2, a mixture of lithium, nickel, and
other metal nitrate salts are combined with a pore former salt and dissolved in a
solvent. Upon heating or removal of water or other solvent, a homogeneous
distribution of elements is obtained for the Li(Ni1-xMx)O2, (where M = Co, Ni, or Mn)
cathode material. It should be noted that decomposition and reaction of the metal
nitrate salt results in the release of large amounts of toxic and corrosive NOx gases.
While this method gives useful material, the inherent difficulty is that the elements to
be combined must be soluble in the melt. In addition, if the soluble metal salt is not
available for a given element, the element may not be able to be dispersed
homogeneously. Ti dopant can be incorporated into the Li(Ni1-xMx)O2, (where M =
Co, Ni, or Mn) cathode material by heating of a mixture of TiO2 particles with
nitrate/aqua salts of nickel, manganese and/or cobalt. However, this procedure is time
consuming due to the several steps needed and the lack of suitable starting materials
limits the scope of this procedure. An additional limitation of this procedure is that the
dopant is limited to feed materials that are soluble in the feed solution. It is not known
how well the size and morphology of the cathode material can be controlled using this
technique.
Another technology used to prepare a "doped" metal hydroxide or oxyhydroxide
material is physical mixing or blending. Using this technology, dry powders, for
example Co(OH)2 and Mg(OH)2, can be mixed together using a suitable blending
procedure. If two materials are difficult to blend and tend to segregate, achieving a
homogeneous blend can be challenging.
If the physically mixed materials can be well blended, a common occurrence is that the
Mg(OH)2 only coats the surface of the Co(OH)2 particles and does not become
completely entrained within the Co(OH)2. The consequence of this is that the Mg is
not homogeneously doped throughout the core of the Co(OH)2 particles. To achieve a
complete homogeneous distribution of dopant metal in the core, the products must be
heated to allow diffusion of the Mg dopant coating into the core of the Co(OH)2
precursor. It has been noted that the diffusion of the dopant material is highly
dependant on the mobility of the ions during solid state firing and on the temperature
of the solid state reaction. The increased dependence on higher firing temperatures
leads to over-sintered, aggregated (instead of agglomerated) products. In addition to
the non-homogeneous doping, the blending step can be an additional processing step
and would add increased costs to the overall process.
Similar to the dry physical mixing strategy, an additional doping technology involves
preparing a well mixed slurry of a raw material. An example of this would be a slurry
of a metal hydroxide, for example Co(OH)2, and a dopant, for example Mg(OH)2 in a
suitable solvent, for example water. The well mixed slurry can be considered to be
"doped" with the dopant at this stage. The slurry can be dried to yield a material with
a homogeneous distribution of dopant together with the raw material. However, as in
the dry blending example, the raw material would have only a surface coating of
dopant, not a homogeneous core doping, and the effectiveness of the mixing depends
strongly on the ability for the two components to mix and dry without segregation.
It is the scope of the present invention to overcome the above mentioned problems in
homogeneously distributing dopants in metal hydroxide or oxyhydroxide material.
In a first general embodiment, the invention covers a heterogeneous metal bearing
material, comprising a host material composed of primary particles agglomerated into
secondary particles, and a particulate dopant material, characterised in that the
particulate dopant material is homogeneously distributed within the secondary particles
of said host material.
In a particular embodiment, the host material is either one or a mixture of a metal
hydroxide, oxyhydroxide, oxide, oxycarbonate, carbonate, or oxalate. In another
embodiment the heterogeneous metal bearing material has the general formula (dopant
material)a(host material)b, where a and b are weight fractions, with 0 < a < 0.4,
preferably 0.001 < a < 0.4, and more preferably 0.001 < a < 0.02, and where b = 1 - a.
The dopant material is preferably either one or more of MgO, Cr2O3, ZrO2, Al2O3, and
TiO2, and is in the form of nanoparticles. The dopant material can also be either one of
MgF2 and CaF2, or another water insoluble metal halide, in the form of nanoparticles.
Most preferably, the dopant material is TiO2 and the host material is either one or a
mixture of NixMnyCoz hydroxide, oxyhydroxide, and oxide, where x,y,z are atomic
fractions, with 0= x = 1,0 = y =1,0=z=1, and x+y+z = 1. The dopant material
should preferably have a size range of > 5 nm and = 200 nm, and preferably between
10 and 50 nm.
In yet another preferred embodiment the secondary particles of the heterogeneous
metal bearing material are spherical.
In a second general embodiment, a process is described for homogeneously
distributing a particulate dopant material in a host material composed of primary
particles agglomerated into secondary particles, thereby obtaining a heterogeneous
metal bearing composite material, comprising the steps of:
- providing a first flow comprising a solution of a precursor of the host material,
- providing a second flow comprising a precipitation agent,
- providing a third flow comprising a complexing agent,
- providing a quantity of insoluble particulate dopant material, either in one or more of
said first, second and third flows, or in a fourth flow consisting of a suspension of said
particulate dopant material, and
- mixing said first, second and third flow, and, if present, said fourth flow, thereby
precipitating said host material and said dopant.
In this process, the solution of the precursor is preferably an aqueous metal salt
solution, and also the suspension of the dopant material is a suspension in water and a
suspension stabilizing agent. In a preferred embodiment, the particulate dopant
material consists of stabilized nanoparticles, preferably of metals or metal oxides, and
the precursor is either one or a mixture of a metal nitrate, chloride, halide, and sulphate
powder.
More preferably, the dopant material is either one or more of MgO, Cr2O3, ZrO2,
Al2O3, and TiO2, and has a size range of > 5 nm and = 200 nm.
In a third general embodiment, the heterogeneous metal bearing material is used for
manufacturing a cathode material for a secondary battery, by firing said material with a
lithium source. Here, preferably the dopant material is either one of MgO, Cr2O3,
ZrO2, Al2O3, and TiO2, and the cathode material is a lithium transition metal oxide.
More preferably, the dopant material is Al2O3, and the cathode material is LiNiO2.
Brief Description of Drawings
Figure 1 is a set of cross sectional EDS SEM micrographs of a TiO2 doped
NixMnyCoz(OH)2 particle showing homogeneous Ti distribution throughout the interior
of the secondary particles.
Figure 2 is a set of surface EDS SEM micrographs of a TiO2 doped NixMnyCoz(OH)2
particle showing homogeneous Ti distribution on the surface of the secondary
particles.
Figure 3 is a set of SEM micrographs of TiO2 doped NixMnyCoz(OH)2.
The invention provides a new type of nanoparticle doped precipitate and a general
procedure for preparing this new type of material. Specifically, but not limited to, this
invention provides a general method to produce TiO2 doped metal hydroxide or
oxyhydroxide products through continuous precipitation. The general procedure can
be applied to prepare a wide variety of doped materials by combining a feed of
nanoparticles with other feeds to be precipitated during a reaction.
For example, spheroidal NixMnyCoz(OH)2 (where x, y, z = 1 and x+y+z = 1), ranging
in D50 from 8-21 µm, can be synthesized and used as a starting material for many
applications, including, but not limited to, the synthesis of Ti doped LiNixMnyCozO2
(where x, y, z < 1 and x+y+z = 1) for use as a cathode material in secondary batteries.
The present invention can also be used as a general method to incorporate a dopant
into a material in which it is usually not stable; or to dope precipitated materials with
insoluble dopants including, such as, but not limited to MgO, Cr2O3, ZrO2, Al2O3, or
TiO2 and any general metal oxide, metal halide, metal compound, or elemental metal
nanoparticle. This method is also a general method to introduce a normally unnatural
dopant element into a precursor which can later be incorporated into a final material.
In the synthesis procedure according to this invention, a feed of insoluble metal oxide
nanoparticles are introduced during the precipitation of a metal hydroxide or
oxyhydroxide. In general, the metal oxide nanoparticles are introduced into a reactor
along with a metal salt solution, an alkaline earth hydroxide, and a complexing agent.
However, any design that results in the preparation of a composite particle containing a
phase of major product, for example M(OH)2 and a minor phase (between 0.1-50%,
and more typically between 0.1-10%) of dopant nanoparticles is within the spirit of the
invention.
In a preferred process according to the invention, at least two flows of reactants are
added to a reactor. At least one of the flows contains a basic composition like NaOH
and/or NH4OH, forming the anion of the precipitate to be obtained, and another flow
contains disolved metal like MSO4, forming the cation of the precipitate. During the
addition of the flows to the reactor, dopant nano-sized particles are present in the
reactor. These nano particles are preferably added directly to the reactor or
alternatively are fed into any one of the flows, preferably in the form of a dispersed
solution containing the nano particles, but the addition can also be in the form of a fine
powder.
Hence, the following supply flow schemes to the reactor can be observed:
(1) Flow 1: precipitation agent (e.g.NaOH), Flow 2: host material solution (e.g.
MSO4), Flow 3: solution of a complexing agent (e.g. NH3), Flow 4: Nano dispersion of
dopant (e.g. TiO2)
(2) Flow 1: precipitation agent (e.g.NaOH), Flow 2: host material solution (e.g.
MSO4), Flow 3: solution of a complexing agent (e.g. NH3), Nanoparticles: add as a
powder to one of the flows or to the mixture of one or more of the Flows 1, 2, 3
(3) Nanoparticles are dispersed in the "starting water" or "starting ammonia" in the
reactor, Flow 1: precipitation agent (e.g.NaOH), Flow 2: host material solution (e.g.
MSO4), Flow 3: solution of a complexing agent (e.g. NH3).
After reaction, the precipitated slurry is collected and filtered and the solid is washed
with water and then dried to yield metal hydroxide particles doped with nanoparticles.
If the precipitate or transition metal ions become oxidized during the reaction or during
one of the other processing steps, an oxyhydroxide or oxide of some other chemical
composition is obtained.
The choice of a soluble metal salt is not restrictive. Soluble metal salts, including
nitrates, chlorides, halides, and sulphates may also be used, depending on the
application. For the precipitating agents, besides NaOH, for example LiOH, KOH,
carbonate, and oxalate salts, may also be used to precipitate the metal salt out of its
solution. Complexing agents are typically chosen from soluble amine salts or
molecules, including but not limited to NH3, ethylenediaminetetraacetate salts, urea, or
other known complexing agents. The precipitated host material, for example
NixMnyCo2(OH)2, is usually a hydroxide, but could also be another metal hydroxide,
oxide, oxyhydroxide, oxycarbonate, carbonate, or oxalate precipitate that is co-
precipitated with the dopant nanoparticles.
The nanoparticle of choice should be of an appropriate size so that it is possible for it
to fit among the primary particles of the host material. It is preferable to have a
sufficiently small nanoparticle to allow the nanoparticle to become embedded
throughout the NixMnyCo2(OH)2 particle. The size requirement is generally less than
200 nm and larger than 10 nm, but nanoparticles of larger or smaller size may be
acceptable depending on the composition and morphology of the composite particle
required. In general, smaller nanoparticles would be advantageous if deep diffusion
into the core of the particle is needed. Hence, in the spirit of this invention, it is
possible to introduce any nanoparticle as a dopant so long as it may be encompassed
by the host material.
The doping metal oxide is not limited to TiO2, and any other stabilized solution of
metal oxide, metal halide, metal salt, or metal nanoparticles with appropriate size may
be used. The choice of nanoparticle requires that it is of appropriate size and will not
dissolve appreciably, or is highly insoluble in the reaction mixture or feed solution that
the nanoparticle comes in contact with. Other examples of typical metal oxides
include, but are not limited to, Al2O3, MgO, Zr2O3, and Cr2O3. Other nanoparticle
examples of metal halides include CaF2 and MgF2.
The nanoparticle can be introduced in several forms, but the preferred method is to
introduce the nanoparticle as an aqueous dispersion as a separate feed. Other possible
methods of introducing the nanoparticle feed include: as a powder directly into a
reactor; as a coreactant in any one of the metal sulphate, caustic, or aqua feeds; as an
aqueous or non-aqueous dispersed or slurried feed in a separate line; as a seed solution
already contained in the reactor; added as part of a batch reaction; added continuously
during a continuous precipitation; added as part of a reaction mixture during an
autoclave or high temperature synthesis; added intermittently at only certain times
during a reaction.
In a preferred embodiment of the invention, a stabilized aqueous solution of TiO2
nanoparticles, an aqueous solution of nickel, manganese, cobalt sulphate, caustic, and
aqua ammonia are introduced into a stirred and heated reactor and the precipitated
material is collected. Thus, crystalline TiO2 doped NixMnyCoz(OH)2 is prepared under
the spirit of the preferred embodiment.
The reaction can be typically performed using continuous precipitation using an
overflow reactor and can be controlled by adjusting and monitoring the pH throughout
the experiment. Experiments may also be performed without pH control, by adjusting
the feed rates of the reactants. Another possible reaction configuration can be carried
out using an autoclave reactor or a batch reactor. The continuous precipitation process
is typically performed between 20 °C and 90 °C, but higher or lower temperatures can
also be used. The typical solvent for the reaction is water, but other solvents, for
example glycols, alcohols, acids, and bases can also likely be used.
In a typical reaction, the pH (temperature uncompensated) is controlled between values
of 10.4 to 11.3, with the preferable range being between 10.8 and 11.0. In general, a
higher pH will result in the precipitation of smaller secondary particles, while a lower
pH will result in the precipitation of larger secondary particles. The resulting
spheroidal TiO2 doped NixMnyCoz(OH)2 has D50 particle size volume distribution
values between 5-50 µm and spans ranging from 0.5 to 2.0. More precisely, the steady
state production of TiO2 doped NixMnyCoz(OH)2 will result in D50 particle sizes
ranging from 6-21 µm with spans ranging from 0.9 to 1.3. The span is defined as
being (D90-D10)/D50.
Alternatively, a less spheroidal agglomerated TiO2 doped NixMnyCoz(OH)2 (where
x+y+z = 1) material can be produced by increasing the pH. This material retains water
more easily and has steady state D50 particle sizes ranging from 4-14 µm with spans
typically greater than 1. It should be noted that non-steady state conditions can result
in monodisperse spheroidal particles with D50 particle sizes less than 14 µm and spans
less than 1.
The primary platelet sizes of the precipitated TiO2 doped NixMnyCoz(OH)2 range from
10 nm to 2000 nm, with typical primary platelet sizes between 50-400 nm. The tap
density of the TiO2 doped NixMnyCoz(OH)2 ranges from 0.7-1.5 g/cm3 and more
typically is between 1.2-1.5 g/cm3. In general, larger TiO2 doped NixMnyCoz(OH)2
(where x+y+z =1) secondary particles and primary particle thicknesses will give
higher tap densities. The apparent density of this material ranges from 0.3-1.2 with
typical values of 0.8-1.2 g/cm3.
The precipitated TiO2 doped NixMnyCoz(OH)2 powder from the preferred embodiment
is a composite of two separate phases: one of TiO2 and one of NixMnyCoz(OH)2. The
composite particles are usually composed of collections of primary particles of
NixMnyCoz(OH)2, with thicknesses ranging between 20-500 nm and more typically
between 50-200 nm. Interdigitated and embedded between the primary platelets of
NixMnyCoz(OH)2 are the TiO2 nanoparticles. The TiO2 is embedded throughout the
NixMnyCoz(OH)2 particle and is not solely on the surface of the particle.
The composite secondary particles typically have a defined spheroidal shape with a
D50 range between 1-50 urn and more typically between 5-25 µm. It is during the
precipitation that the PSD is typically controlled, although precipitated material can
also be prepared using a gel preparation and then processed to a smaller size. Other
processing methods, including grinding, milling, or other attrition techniques, may be
used to prepare particles of appropriate size.
This composite can be used for the preparation of Ti doped LiMO2 for use in cathode
battery materials. In a typical synthesis, the TiO2 doped NixMnyCoz(OH)2 is blended
with a Li source, for example Li2CO3, but other Li sources, for example LiOH or
LiNO3, can be used. The reaction mixture is then heated to produce a Ti doped
LiMO2.
Example 1
A mixture of NiSO4 6H2O, MnSO4.H2O, and CoSO4.7H2O were dissolved in water
to a summed total metal concentration of 55 g/L. A second feed of aqueous TiO2
suspension was used as the dopant feed. The doped metal hydroxide/oxyhydroxide
was then precipitated by continuously adding the 55 g/L metal Ni/Mn/CoSO4 solution
(1:1:1 Ni:Mn:Co molar ratios), a 0.6% TiO2 suspension, an aqueous 25% NaOH
solution, and a 260 g/L NH3 solution through four tubes into an overflow reactor. The
reaction was controlled via a pH feedback system to control the growth and
composition of the precipitated material. The overflow reactor can be seeded with a
solution of NixMnyCo2(OH)2 (where x+y+z = 1) seed, NaOH, Na2SO4, ammonia, and
water. Alternatively, the reaction can be started in the absence of seed using a reactor
filled with water. The resulting overflow slurry was collected and the light brown
solid was separated from the supernatant by filtration. After washing with water, the
precipitated solid was dried in a convection oven at 70 °C to a constant mass. After
drying, the powder became black. The black powder was highly flowable and easily
processed and passed without difficulty through a 100 mesh screen. After screening,
the powder was sent for analysis.
Chemical analysis of the precipitated material confirmed a composition consistent with
a Ni0.32Mn0.32Co0.32Ti0.04 metal atomic ratio. The oxygen and hydrogen levels were not
measured, but the black colour of the powder indicated that oxidation was likely. The
change in oxidation state was most certainly an indication that the precipitated material
was no longer the simple unoxidized M(OH)2, and that the powder was likely an
oxidized form consistent with an oxide or oxyhydroxide. Powder X-ray diffraction
analysis of the powder was consistent with a composite material containing a mixture
of TiO2 and slightly oxidized ß-Ni0.33Mn0.33Co0.33(OH)2.
SEM micrographs (see Figure 3) of the black powder revealed that the powder was
made up of spheroidal secondary particles ranging in D50 from 1-15 µm in diameter.
The secondary particles were composed of primary particles with thicknesses ranging
from 20-200 nm. As shown in the SEM analysis, the secondary particles were coated
with small particles. It is likely that the small particles on the surface of the secondary
particles of Ni0.33Mn0.33Co0.33(OH)2 are TiO2 nanoparticles. Cross sectional SEM EDS
micrographs (see Figure 1) of the precipitated TiO2 doped Ni0.33Mn0.33Co0.33(OH)2
revealed that the Ti, Ni, Mn, and Co were also homogeneously distributed throughout
the core of the hydroxide material. Additionally, surface SEM EDS micrographs
reveal that there is a homogeneous distribution of Ti, Ni, Mn, and Co on the surface of
the Ni0.33Mn0.33Co0.33(OH)2 particles, (see Figure 2)
Example 2
Aqueous mixtures of CoSO4, aqua ammonia, sodium hydroxide, and a TiO2 dispersion
were continuously delivered through 4 separate feed tubes into a stirred reactor
containing seed solution. The pH of the reactor solution was adjusted to a pH of 11.5
(temperature compensated) using a pH feedback loop that regulated the flow of the
sodium hydroxide feed. The seed solution was made up of a slurry of Co(OH)2,
sodium hydroxide, sodium sulphate, and aqua ammonia . The overflow from the
reactor was collected, filtered, washed with water, and dried in a convection oven at
70 °C to constant weight. The resulting flowable, pink, TiO2 doped Co(OH)2 powder
was collected and analyzed.
The elemental analysis of the powder was consistent with the composition
[TiO2]0.005[Co(OH)2]0.995. SEM analysis revealed speroidal agglomerates ranging in
secondary particle size from < 5 µm to 25 µm, with primary particle thicknesses
ranging between 50-500 nm. The tap and apparent density of the material varied with
secondary and primary particle sizes, and precipitate shape, but a sample with a D50 of
15.06 µm and a span of 0.84, had a tap density of 1.09 g/cm3 and an apparent density
of 0.72 g/cm3.
Example 3
In this example, performed according to the general outline of Example 2, a more
concentrated TiO2 feed dispersion was delivered using a lower flowrate and a similar
product was obtained. A powder was obtained that was consistent with the
composition [TiO2]0.005[Co(OH)2]0.995- This sample had a D50 of 13.37 µm, a span of
0.74, a tap density of 1.06 g/cm3 and an apparent density of 0.67 g/cm3.
Example 4
In this example, performed according to the general outline of Example 2, a more
concentrated TiO2 feed dispersion was used and a similar product was obtained. A
powder was obtained that was consistent with the composition
[TiO2]0.010[Co(OH)2]0.990. This sample had a D50 of 13.43 µm, a span of 0.80, a tap
density of 1.25 g/cm3, and an apparent density of 0.87 g/cm3.
Example 5
In this example, performed according to the general outline of Example 2, an aqueous
mixture of MgSO4 and CoSO4 was used instead of the typical CoSO4 feed. The TiO2
feed dispersion was delivered using a lower flowrate and a similar product was
obtained. A powder was obtained that was consistent with the composition
[TiO2]0.0025[Mg0.0025Co0.9975(OH)2]0.975. This sample had a D50 of 15.97 µm, a span of
0.75, a tap density of 1.27 g/cm3 and an apparent density of 0.90 g/cm3.
Claims
1. A heterogeneous metal bearing material, comprising a host material composed of
primary particles agglomerated into secondary particles, and a particulate dopant
material, characterised in that the particulate dopant material is homogeneously
distributed within the secondary particles of said host material.
2. A heterogeneous metal bearing material according to claim 1, wherein said host
material is either one or a mixture of a metal hydroxide, oxyhydroxide, oxide,
oxycarbonate, carbonate, or oxalate.
3. A heterogeneous metal bearing material according to claim 2, wherein said
heterogeneous metal bearing material has the general formula (dopant material)a(host
material)),, where a and b are weight fractions, with 0 < a < 0.4, preferably 0.001 < a <
0.4, and more preferably 0.001 < a < 0.02, and where b = 1 - a.
4. A heterogeneous metal bearing material according to any one of claims 1 to 3,
wherein said dopant material is either one or more of MgO, Cr2O3, ZrO2, Al2O3, and
TiO2, and is in the form of nanoparticles.
5. A heterogeneous metal bearing material according to claim 3, wherein the dopant
material is TiO2 and the host material is either one or a mixture of NixMnyCoz
hydroxide, oxyhydroxide, and oxide, where x, y, z are atomic fractions, with 0 = x = 1,
0 = y = 1,0 = z = 1, and x+y+z = 1.
6. A heterogeneous metal bearing material according to any one of claims 1 to
5,wherein said secondary particles of the heterogeneous metal bearing material are
spherical.
7. A heterogeneous metal bearing material according to any one of claims 1 to 6,
wherein said dopant material is either one of MgF2 and CaF2, or another water
insoluble metal halide, and is in the form of nanoparticles.
8. A heterogeneous metal bearing material according to any one of claims 1 to 7,
wherein said dopant material has a size range of > 5 nm and = 200 nm, and preferably
between 10 and 50 nm.
9. Process for homogeneously distributing a particulate dopant material in a host
material composed of primary particles agglomerated into secondary particles, thereby
obtaining a heterogeneous metal bearing composite material, comprising the steps of:
- providing a first flow comprising a solution of a precursor of the host material,
- providing a second flow comprising a precipitation agent,
- providing a third flow comprising a complexing agent,
- providing a quantity of insoluble particulate dopant material, either in one or more of
said first, second and third flows, or in a fourth flow consisting of a suspension of said
particulate dopant material, and
- mixing said first, second and third flow, and, if present, said fourth flow, thereby
precipitating said host material and said dopant.
10. Process according to claim 9, wherein said solution of the precursor is an aqueous
metal salt solution, and said suspension of the dopant material is a suspension in water
and a suspension stabilizing agent.
11. Process according to claims 9 or 10, wherein the particulate dopant material
consists of stabilized nanoparticles, preferably of metals or metal oxides, and the
precursor is either one or a mixture of a metal nitrate, chloride, halide, and sulphate
powder.
12. Process according to any one of claims 9 to 11, wherein said dopant material is
either one or more of MgO, Cr2O3, ZrO2, Al2O3, and TiO2, and has a size range of > 5
nm and < 200 nm.
13. Use of the material according to any one of claims 1 to 8 for manufacturing a
cathode material for a secondary battery, by firing said material with a lithium source.
14. Use according to claim 13, wherein the dopant material is either one of MgO,
Cr2O3, ZrO2, Al2O3, and TiO2, and the cathode material is a lithium transition metal
oxide.
15. Use according to claim 14, wherein the dopant material is Al2O3, and the cathode
material is LiNiO2.

This invention describes a heterogeneous metal bearing material, comprising a host material composed of primary
particles agglomerated into secondary particles, and a particulate dopant material, characterised in that the particulate dopant material
is homogeneously distributed within the secondary particles of said host material. In particular, the dopant material is TiO2 and the
host material is either one or a mixture of NixMnyCo2 hydroxide, oxyhydroxide, and oxide, with 0 ≤ x, y, z ≤ 1. and x+y+z = 1.