Nanoparticle doped precursors for stable lithium cathode materiat.
The invention relates to precursors for cathode materials for secondary batteries, obtained
by the precipitation of heterogeneous metal bearing material, that is homogeneously doped
with a nanoparticle metal oxide, metal halide, metal anion, or elemental metal component.
Compared to Ni-Cd and Ni-MH rechargeable batteries, Li-ion batteries boast an enhanced
energy density, mainly due to their higher 3.6 V working voltage. Since their
commercialization in 1991 by SONY, Li-ion batteries have seen their volumetric energy
density increase continuously. This has been initially realized by optimizing cell design,
accommodating more active electrode materials in a fixed volume cell. Later efforts
concentrated on improving the energy density of the electrodes. Using a high density active
electrode material is another way to achieve this goal. As LiCoO2 still continues to be used as
positive electrode material for the majority of commercial Li-ion batteries, a highly dense
variety of this material is in demand.
In WO2009/003573 such a high density LiCoO2 material has been disclosed. It provides a
relatively coarse-grained electrochemically active LiCoCh powder, without significant Li-
excess, and having a d50 of more than 15 urn, a BET of less than 0.2 m2/g. The mentioned
particle size is evidently a primary particle size, and the particles are neither agglomerated
or coagulated, nor aggregated.
However, this material shows various limitations in a rechargeable lithium battery. One
basic limitation originates from the surface area dilemma. Increasing the rate performance
(i.e. high power) can be met by increasing the surface area because the solid-state lithium
diffusion length can be decreased; which results in an improved rate performance. However,
a high surface area increases the area where unwanted side reactions between electrolyte
and charged cathode take place. These side reactions are the reason for poor safety, poor
cycling stability at elevated voltage and of poor storage properties of charged cathodes at
elevated temperature. Furthermore, high surface area materials tend to have a low packing
density which reduces the volumetric energy density.
Recent findings have shown that doping LiCoO2 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. The advantages of Ti doping for
LiCoO2 have been mentioned in US6,277,521.
As for most cathode materials for use in secondary batteries, their preparation often makes
use of a particular precursor. The precursor can then be fired with a lithium source to
prepare a cathode material. 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. In co-pending application
WO2009/074311 various methods for preparing cathode precursor material were discussed,
amongst others precipitation, coprecipitation, spray drying, spray pyrolysis, physical mixing
or blending, also using slurries. All of these methods have serious problems in achieving good
homogeneous doping, especially for Ti doping using a material like nanoparticles of Ti02.
As initially said, an essential feature of LiCo02 is its high density. The crystallographic
density is higher than other cathode materials, namely 5.05 g/cm3, and LiCo02 shows a good
performance even if particles are relatively large and compact. The large and compact
particles pack well and thus allow to achieve electrodes with high density. High density
electrodes allow to insert a larger mass of active LiCo02 into the confined space of a
commercial cell. Thus a high density of LiCo02 is directly related to a high volumetric
density of the final commercial lithium battery. A preferred morphology to achieve high
density are compact - mostly monolithic, non-agglomerated - particles. A typical particle
size (D50) is at least 10 or even 15 urn, and typically it is less than 25 urn.
There are two major preparation routes to prepare such monolithic LiCo02. In the first route
a source of cobalt (like C03O4) with relatively small particle is mixed with a source of lithium
(like Li2C03) and fired at sufficient high temperature with a sufficient excess of lithium.
During sintering, the small C03O4 particles sinter together and particles grow to the desired
size distribution, in the second, alternatively route, relatively large and dense particles of a
cobalt source are used. During sintering particles tend to sinter independently. There is a
densification within a particle, but not much inter-particle sintering. A problem happens if
applying these standard methods to prepare Ti doped LiCo02.
The first method basically results in a failure. If a mixture of Ti02, small particles Co304 and
a source of lithium is sintered, by an - to us unknown and surprising mechanism -
inter-particle sintering is very much suppressed. As a result a high surface area LiCo02
consisting of heavily agglomerated particles is achieved. The preferred morphology
mentioned before is only achieved after applying unrealistically high sintering temperature
or much larger Li excess. Much higher sintering temperature increases the cost significantly -
equipment investment, live time and energy use. Much larger Li excess results in poor
performance.
The second obvious method to prepare Ti doped LiCo02 is as follows: a relatively dense
cobalt precursor (like Co(OH)2 with large particles size, a source of lithium (like Li2C03) and
a source of titanium (like Ti02) are mixed, followed by sintering. In this case - where the
Ti02 is not well distributed within the particle - we observe an inhomogeneous final product.
The reason is that Ti02 has very poor mobility during sintering, so wherever in the mixture a
few Ti02 particles are agglomerated the final LiCo02 will show a region with much higher
Ti02 concentration. As a result, the Ti02 doping with low doping level (0.1 - 0.5 molfc) is not

efficient. At higher levels a benefit is observed, but because of the poor Ti mobility it is
assumed that the inside of the LiCo02 particles is basically free of Ti and the full benefit of
Ti doping cannot be achieved.
A third method to prepare high density Ti02 doped LiCo02 is a two step firing. In a first firing
a LiCo02 precursor with preferred morphology is prepared. This L1C0O2 precursor is mixed
with Ti02, typically at least 0.75 mol% and less than 2 mol% (smaller doping levels are not
efficient, the reason is the same as in the second method - any Ti02 agglomerate will cause
a Ti02 enriched region resulting in a non-homogenious final LiCo02). After sintering it is
assumed that the LiCo02 core is free of Ti02 and the full benefit of Ti doping is not
achieved.
In US2007/0264573 A1 on the other hand an aqueous solution of Mg carbonate, Al and Ti
lactate solution is mixed with a Co hydroxide slurry, and after wet ball milling the slurry is
spray-dried for granulation. These precursor granules are mixed with Li carbonate and
sintered at lOOO'C to obtain a Li Co-Mg-Al-Ti oxide. Since it is generally known that such a
spray-drying operation is carried out at a temperature below 120°C, and since Ti lactate is a
fairly stable compound that will crystallize at such temperatures - since it will only
desintegrate to form Ti dioxide at temperatures over 200° C - the spray-dried precursor does
not contain Ti02 in the form of nanoparticles being homogeneously distributed within the
precursor.
It can further be mentioned that in CN1982219 A a Li Co-Ni-Mn oxide doped with Al, Ti, Mg
and/or Cr is obtained by co-deposition, whilst in CN101279771 A a Mg, Al and/or Ti source
are mixed in a cobalt nitrate solution which is precipitated as a doped cobalt hydroxide.
It is the scope of the present to provide for a manufacturing method for a cathode material
having a high rate performance, showing high stability during extended cycling at high
charge voltage, and having a particularly high pellet density. The high temperature storage
properties are also to be improved. This can be achieved by the use of precursors that
overcome the above mentioned problems in homogeneously distributing dopants in metal
hydroxide or oxyhydroxide material.
Viewed from a first aspect, the present invention can provide a precursor compound of a
titanium doped lithium cobalt oxide powder for use as an active positive electrode material
in lithium-ion batteries, said precursor compound consisting of either one or more of a non-
sintered agglomerated cobalt oxide, hydroxide and oxy-hydroxide powder having a
secondary particle size with a d50 of more than 15 Mm; said agglomerated cobalt oxide,
hydroxide and oxy-hydroxide powder comprising Ti02 in the form of nanoparticles being

homogeneously distributed within said agglomerated powder, with a Ti content of between
0.1 and 0.25 mol%.
In one embodiment, the lithium cobalt oxide powder further comprises Mg as doping
element with a Mg content between 0.1 and 2 mol%. In another embodiment the Ti02
nanoparticles have a size range of > 5 nm and < 200 nm, and in still another embodiment
between 10 and 50 nm.
By 'agglomerated' is understood that the secondary powder particles are decomposed in their
primary particles by applying light to mild forces, like e.g. with soft milling. 'Aggregated'
powders (also called 'hard agglomerates') on the contrary need excessive force to
decompose, or cannot be decomposed into their primary particles.
Viewed from a second aspect, the present invention can provide the use of the precursor
compound described before in the manufacture of a lithium cobalt oxide powder for use as
an active positive electrode material in lithium-ion batteries, said lithium cobalt oxide
powder having a Ti content of between 0.1 and 0.25 mol%, by firing said precursor with a
lithium source. In one embodiment, the lithium cobalt oxide powder has a d50 of more than
10 pm and in another embodiment more than 15 um, and in both embodiments a specific
surface area (BET) of less than 0.25 m2/g, or even less than 0.20 m2/g.
Viewed from a third aspect, the present invention can provide a single firing process for
manufacturing the lithium cobalt oxide powder described before, comprising the steps of:
- providing for the precursor compound mentioned before,
- mixing said precursor compound with a Li source, preferably lithium carbonate, according
to a Li to Co ratio R between 1.04 and 1.07, and
- firing said mixture with a single firing at a temperature T between 960 °C and 1020 "C.
Figure 1a & b: SEM micrograph (2000x magnification) of samples with 0.25 mol% Ti and 0.5
mol% Mg: Fig. 1a: sample LC0193 (left) and Fig. 1b: LC0227 (right)
Figure 2a & b: SEM micrograph (5000x magnification) of samples with 0.75 mol% Ti and 0.5
mol% Mg: Fig. 2a: sample LC0199 (left) and Fig. 2b: LC0233 (right)
Figure 3: SEM micrograph of samples without Ti and with 0.5 mol% Mg: sample LC0190 (left)
and LC0223 (right)

Figure 4: Electrochemical performance of undoped LiCo02: sample LC0189. Left: discharge
profiles at different rates (from left to right:) 3C, C (discharge in 1 hr), C/2, C/10 (each
time showing voltage (V) against cathode capacity (mAh/g)); middle: stability (voltage (V)
against capacity (mAh/g)- from right to left: Cycle 7, 31 (both at C/10), 8, 32 (both at 1C));
right: fade (capacity (mAh/g) against cycle number - line with circles: charge; line with
stars: discharge)
Figure 5: Electrochemical performance of LiCo02 with 0.25 mol% Ti: sample LC0192
(experiments as described in Fig. 4)
Figure 6a & b: SEM micrograph (2000x magnification) of samples with 0.25 mol% Ti and
varying Mg: Fig. 6a: sample LC0322 (left) and Fig. 6b: LC0329 (right)
Figure 7: Electrochemical performance of LiCoCh with 0.25 mol% Ti: sample LC0189
(experiments as described in Fig. 4)
Figure 8: Electrochemical performance of LiCo02 with 2 mol% Mg and 0.25 mol% Ti: sample
LC0329 (experiments as described in Fig. 4)
Figure 9 a & b (top and bottom): Electrochemical performance of LiCo02 with 0.2 mol% Ti:
samples LC0315 (Fig 9a) and 316 (Fig 9b) (experiments as described in Fig. 4)
Figure 10: Pellet density (g/cm3) as a function of mean particle size D50 (urn)
Figure 11 a & b: Discharge voltage profiles during extended cycling at 1C (cell voltage
against capacity): 11a: sample LC0214 (0.25 mol% Ti); 11b: sample LC0207 (no Ti). For each
from right to left: cycles 2, 50, 100, 200, 300 a 500.
The cathode materials for secondary batteries using the type of precursors described before
can exhibit an increased stability besides high capacity and energy density, and they can
also meet the necessary power requirements, which means that the active cathode material
itself and the battery as a whole have a sufficient high rate performance.
An important aspect of the invention is that it can provide precursors of a new type of
nanoparticle doped precipitate. In that sense, in a first embodiment a method to
incorporate a dopant into a material in which it is usually not stable can be provided. In
another embodiment, a method can be provided to dope precipitated materials with
insoluble dopants including, such as, but not limited to MgO, Cr203, Zr02) Al203, or Ti02 and
any general metal oxide, metal halide, metal compound, or elemental metal nanoparticle.
In still another embodiment, a method can be provided to introduce a normally unnatural
dopant element into a precursor which can later be incorporated into a final material.

Because, for example, Ti02 Is well dispersed within the secondary particles of the precursor
compound the diffusion length is short and the cathode material for secondary batteries
prepared with this precursor, such as IjCoOj, is homogeneous. No region rich in Ti02 is
detected when analysing with EDX. Because of the well distributed Ti already small doping
amounts of 0.1 -0.25 mo\X give the full benefit of Ti doping. Furthermore, by a mechanism
that is not yet fully understood - it is surprisingly observed that small Ti doping levels cause
a significant increase of pellet density. This is a very desired effect because It allows to
increase the volumetric energy density of commercial lithium batteries, Other particular
aspects, such as superior rate capability and better stability at high voltage, are illustrated
below.
A example of a process used for homogeneously distributing the particulate dopant material
in the host materials which are the precursors mentioned before, being composed of primary
particles agglomerated into secondary particles, can comprise 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 complexlng 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. This process was already detailed in
WO20097074311.
In this example 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 comprising
a suspension stabilizing agent. In one embodiment, the particulate dopant material consists
of stabilized nanoparticles, such as metals or metal oxides, and the precursor is either one
or a mixture of a metal nitrate, chloride, halide, and sulphate powder. In another
embodiment, the dopant material is either one or more of MgO, Cr20j, ZrO,, AljOj, and TiOj,
and has a size range of a 5 nm and s 200 nm.
As said before, In the example synthesis procedure according to this invention, a feed of
insoluble metal oxide nanoparticles can be Introduced during the precipitation of a metal
hydroxide or oxyhydroxide. It is also possible to introduce the metal oxide nanopartfcles
into n rparrnr airing with a mpral salt soUirjnn, an alkaline earth hydroxide, and a
complexlng agent. In one embodiment, 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 dissolved

metal like CoSQ,, 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,
for example in the form of a dispersed solution containing the nano particles, but the
addition can also be in the form of a fine powder. A possible process to dope the precursor
with Mg is to provide for a C0SO4 solution containing the Mg (as MgS04) in the desired
quantities.
Hence, the following example supply flow schemes to the reactor can be observed:
(1) Flow 1: precipitation agent (e.g.NaOH), Flow 2: host material solution (e.g. Mg doped
C0SO4), Flow 3: solution of a complexing agent (e.g. NH3), Flow 4: Nano dispersion of dopant
(e.g. Ti02)
(2) Flow 1: precipitation agent (e.g.NaOH), Flow 2: host material solution (e.g. Mg doped
CoS04), 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. Mg doped
C0SO4), 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 for
example chosen from soluble amine salts or molecules, including but not limited to NH3,
ethylene diamine tetra-acetate salts, urea, or other known complexing agents. The
precipitated host material, for example Co(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 can be of an appropriate size so that it is possible for it to fit
among the primary particles of the host material. It one example there is provided a
sufficiently small nanoparticle to allow the nanoparticle to become embedded throughout
the Co(OH)2 particle. In one embodiment the size of the nanoparticle is 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 could be advantageous if deep diffusion into the core of the
particle is envisaged.
The choice of nanoparticle focusses on appropriate size and on the fact that it will not
dissolve appreciably, or that it is highly insoluble in the reaction mixture or feed solution
that the nanoparticle comes in contact with.
In an embodiment of the invention, a stabilized aqueous solution of Ti02 nanoparticles, an
aqueous solution of cobalt sulphate, caustic, and aqua ammonia are introduced into a
stirred and heated reactor and the precipitated material is collected. Thus, crystalline Ti02
doped Co(OH)2 is prepared as a Co precursor as used in the second aspect described before.
The reaction can be typically performed using continuous precipitation in 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 for example
performed between 20 °C and 90 °C, but higher or lower temperatures can also be used. An
example solvent for the reaction is water, but other solvents, for example glycols, alcohols,
acids, and bases can also be used.
In another example reaction, the pH (temperature uncompensated) is controlled between
values of 10.4 to 11.3, or even 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 Ti02 doped Co(OH)2 can have D50
particle size volume distribution values between 5-50 urn and spans ranging from 0.5 to 2.0.
In one example, the steady state production of Ti02 doped Co(OH)2 can result in D50 particle
sizes ranging from 6-21 urn with spans ranging from 0.9 to 1.3. The span is defined as being
(D90-D10)/D50.
The primary platelet sizes of the precipitated Ti02 doped Co(OH)2 can range from 10 nm to
2000 nm, with typical primary platelet sizes being for example between 50-400 nm. The tap
density of the Ti02 doped Co(OH)2 can range from 0.7-1.5 g/cm3 and is for example between
1.2-1.5 g/cm3. In general, larger Ti02 doped Co(OH)2 secondary particles and primary
particle thicknesses can give higher tap densities. The apparent density of this material can
range from 0.3-1.2, for example with typical values of 0.8-1.2 g/cm3.
The precipitated Ti02 doped Co(OH)2 powder is for example a composite of two separate
phases: one of Ti02 and one of Co(OH)2. The composite particles can usually be composed of
collections of primary particles of Co(OH)2, with thicknesses that can be between 20-500
nm, for example between 50-200 nm. Interdigitated and embedded between the primary

platelets of Co(OH)2 are the Ti02 nanoparticles. The Ti02 is embedded throughout the
Co(OH)2 particle and is not solely on the surface of the particle.
The composite secondary particles typically can have a D50 range between 1 -50 urn and
more typically between 5-25 um. 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.
With the example aggregated precursor according to the first aspect above, using a suitable
blending ratio of Li to Co, and a single firing step, the primary particles in the end product
grow larger, while there is little change in secondary particle size. Under certain conditions,
such as with a blending ratio of Li to Co between 1.04 and 1.07, and a firing temperature in
the range of 960 to 1020 °C, the primary particles forming the secondary structure can
indeed grow together. In this way, and by using aggregated Co(0H)2, the final lithium cobalt
oxide powder can be prepared cost effectively.
The example precursor product can thus be defined as either one or more of an non-sintered
agglomerated powderous cobalt oxide, hydroxide and oxy-hydroxide, having a secondary
particle size with a d50 of more than 15 um. In one embodiment the primary particles have
a primary particle size with a d50 of less than 5 um. The secondary particles can have a
spherical shape. The cobalt oxide can either be Co304, Co203, or a partially oxidized and
dried Co(OH)2. It is an advantage when the secondary particles of the precursor do not
contain any sintered primary particles, since the desired result is normally obtained using a
single firing step.
The invention may be illustrated by the following experimental details:
Preparation of Ma and/or Ti doped precipitated hydroxide
A series of in total 12 cobalt hydroxide based precursors are prepared in a small pilot plant
continuous precipitation line using the process described above. A flow of Ti02 nano
particles is continuously fed into the rector, and at the same time Mg-doped Co-sulfate
solution, sodium hydroxide solution and NH4OH are added continuously to the reactor.
Precipitated samples are collected after reaching steady state. Each preparation takes more
than one week. After sampling the cobalt based hydroxide is washed and dried.
The intention of this series is to prepare precursors with similar morphology but different
doping. Ti02 doping levels (per 1 mol Co) range from 0 to 0.75 mol%. Mg doping levels per
mol Co vary between 0 and 2 mol%.

ICP elemental analysis confirms that the targeted composition is achieved for all of these
samples. Great care is taken to ensure that the morphology of all these precursors is very
similar. All precursors have a tap density ranging from 1.35 -1.45 g/cm2 and the D50
(particle size distribution, wet method) of 17-21 urn. Morphology, checked by SEM, looks
very similar, showing irregular secondary particles consisting of slightly coarse primary
plate-shaped particles. The Ti02 containing samples have the Ti02 well distributed within
the secondary particles.
Preparation of Mg and/or Ti doped LiCoO?
More than 36 final LiCo02 base samples are prepared from these precursors as follows:
The cobalt hydroxide based precursor is mixed with fine Li2C03 particles, then fired in dry air
at 1015°C, followed by milling and sieving. Typical sample size is 1 kg. The Li:Co molar blend
ratio varies from 1.04 to 1.07.
The final samples are investigated by particle size analysis (PSD, dry method), BET surface
area, SEM microscopy, coin cell testing, pH titration and pellet density. Selected samples
are further tested by elemental analysis (ICP), full cell testing (commercial size Li polymer
cells, including safety tests, storage tests and cycling stability test), electrode density, EDX
cross section, DSC safety estimation etc.
Particle size distribution of LiCo02 is measured using laserdiffraction. A standard analysis of
laser diffraction particle analysis assumes that the particles which created the diffraction
pattern are spheres with various volume. The "D50" is median of the size-volume
distribution, i.e. particles with smaller size contribute 50% to the total volume.
Correspondingly, "D10" and "D90" are the size where smaller particles contribute 10% or 90%
to the total volume.
The specific surface area of LiCo02 is measured with the Brunauer-Emmett-Teller (BET) 5
point method using a Micromeritics Tristar.
Pellet density is measured as follows: 3g of powder is filled into a press from with a
diameter of 1.292 cm. Pressure is applied for 30 sec, whereupon the powder sample
thickness is measured. By knowing its pressed volume and weight the pellet density is
calculated.
Electrochemical performance is tested in coin type cells, with a Li foil as counter electrode
in a litium hexafluorite (LiPF6) type electrolyte at 25 *C. Cells are charged to 4.3 V and
discharged to 3.0 V to measure rate performance and capacity. The capacity retention
during extended cycling is measured at 4.5V charge voltage. Specific capacity of 160 mAh/g
is assumed for the determination of the discharge rates. For example, for discharge at 2 C, a
specific current of 320 mA/g is used.
Rate capability is measured at different discharge rates (as in Fig.4, left):

Cycle 1: C/10, 2: C/5, 3: C/2, 4: 1C, 5: 2C, 6: 3C (1C = 160 mA/g)
For stability and fade measurements (as in Fig. 4, middle and right), the cycling procedure is
continued as follows:
Cycle 7: C/10
Cycle 8: 1C
Cycles 9 to 30: cycled at C/4 charge and C/2 discharge at 4.5-3.0 V
Cycle 31: C/10
Cycle 32: 1C
Good materials should at least have the following properties:
- BET: Small BET surface area, typically below 0.25 or even 0.2 m2/g
- SEM: Preferred are powders comprising dense, compact, monolithic secondary particles -
thus avoiding excessive agglomerates
- Coin cell testing showing:

(a) high rate performance
(b) rectangular shape of discharge profile at higher rate
(c) small change of voltage profile after extended cycling at 4.5V
(d) high capacity retention during extended cycling stability at 4.5V

- Pellet density: as high as possible
- PSD: no excessive number of large or small particles, or Low span (=(D90-D10)/D50) and
monomodal PSD.
The surprising discovery is made that very small amounts of titanium (much below 0.5 mol%)
dramatically improve the performance (pellet density, rate performance, cycling stability)
without sacrificing any other positive property. Also, if the Ti doping level exceeds 0.5
mol%, then it is impossible to obtain the preferred morphology. The particles have high BET
surface and are strongly agglomerated. We furthermore discovered that the benefit of Ti is
completely independent of magnesium doping level.
Generally, the best performance is achieved with 0.25 mol% Ti02 doping or less. In the
presence of Ti02, introducing additional magnesium doping causes a small decrease of
capacity without loosing rate performance, but gaining in safety performance. In the
following aspects of the invention are described by examples:
Example 1
Two cobalt hydroxide precursors, doped with 0.5 mol% Mg and containing 0.25 mol%
dispersed Ti02 nano particles are used to prepare 6 final LiCoG*2 based samples.


All samples have excellent performances. The BET decreases with particle size, and the
pellet density increases. Particularly LC0227 and LC0193 are of interest. They offer the best
compromise between desired particle size, good electrochemical performance and very high
pellet density. Figure 1 shows the SEM micrograph of samples LC0227 and LC0193. We
observe quite compact particles with some edges and faces. This morphology is especially
preferred to obtain high density.

Counterexample 2
Two cobalt hydroxide precursors, doped with 0.5 mol% Mg, containing 0.75 mol% dispersed
Ti02 nano particles are used to prepare 6 final LiCo02 based samples. Sintering conditions
are as in Example 1.

The main difference with the 0.25 mol& Ti doped samples of Example 1 is that the BET is
very large, and the partice size much smaller. With increasing Li:Co, the BET does not
decrease much, and the particle size increases insignificantly. Pellet density could not be
measured reliable, because of strong agglomeration, as will be discussed next.
Figure 2 shows the SEM micrograph of 2 typical samples, LC0199 and LC0233. Note that the
magnificantion is differen from Figure 1t! Obviously, the morphology of these samples,
doped with 0.75 mol% Ti is very different from the 0.25 mol% doped samples. The first are
strongly agglomerated, with small primary crystallites ranging from sub-micrometer to 5 urn,
the latter are large and compact, primary crystallites have about 5-20 urn size.
The strong agglomeration is the reason that pellet density could not be measured reliable,
simply because the agglometarates are braking under the applied force, giving results that
are much too high for the given morphology. Values of 3.59 are measured (the realistic value
is smaller), much below those of Example 1.
6 more samples are prepared using 0.5 mol% Mg doped Cobalt hydroxide, additionally
containing 0.5 mol% Ti. The results are in between those of Example 1 and
Counterexample 2; showing clearly more agglomerated, lower density and higher BET than
those of Example 1.
It is concluded that doping of LiCo02 with more than about 0.25 mol% Ti is undesired.

Counterexample 3
Two cobalt hydroxide precursors, doped with 0.5 mol% Mg without containing dispersed Ti02
nano particles are used to prepare 6 final LiCo02 based samples. Sintering conditions are as
in Example 1.

The main difference with Example 1, at similar particle size, is to be found in a much larger
pellet density. Figure 3 shows the SEM micrograph of samples LC0190 and LC0223. The
p?.rticles are compact, the particle size is comparable, but compared with 0.25 mol% Ti of
/
Example 1, the shape is very different. The shape is more round and sometimes concave.
This morphology is less preferred and results in a much lower pellet density for an identical
size.
Furthermore, the rate performance and stability of 0.25 mol% Ti doped samples of Example
1 is much superior. The numeric values are not so different, but a careful look at the voltage
profiles during cycling and rate performance shows very clear differences.
Figure 4 shows the performance of a typical undoped sample and compares with a 0.25% mol
Ti doped sample. Both samples have quite similar key parameters (PSD, BET, ...). The
profile of 0.25 mol% Ti doped samples, especially at high rate, is much more rectangular -
more steep at the end of discharge - and it remains more rectangular during cycling,
whereas undoped samples show a clear deterioration of discharge voltage profile. A
decrease in fading rate for the 0.25 mol% doped samples is also observed, whereas the Ti02
free sample continues to loose capacity. We conclude that LiCo02 without the inventive Ti
doping has less cycle stability and lower rate performance.

Example 4
Two cobalt hydroxide precursors, undoped or doped with 2 mol% Mg, and also containing
0.25 mol% dispersed Ti02 nano particles, are used to prepare 12 final LiCo02 samples.
Sintering conditions are as in Example 1.

All samples exhibit a high pellet density. All samples showed a similar sintering behaviour
that those of Example 1. Figure 6 (SEM of samples LC0322 6t 329) shows that excessive
agglomerated morphology, observed for larger Ti doping as in Counterexample 2, is absent.
The morphology is quite similar to those of Example 1. Figure 7 and 8 show a similar cycling
performance as observed in Example 1. We conclude that Mg content has very little
influence on the morphology. Typical is the rectangular voltage at higher rate, remaining
rectangular also after extended cycling. The reversible capacity, however, decreases slightly
with increasing Mg doping - this is generally observed for Mg doped LCO.
Counterexample 5
A cobalt hydroxide precursor, doped with 2 mol% Mg and containing 0.5 mol% dispersed Ti02
nano particles is used to prepare 3 final LiCo02 samples. The preferred morphology - as
described in Ex. 1- is not obtained. The samples show excessive agglomeration, similar to

Counterexample 2. Counterexample 5 confirms that a well controlled Ti doping level is
important for morphology, but Mg doping is not.
Counterexample 6
0.20 mol% Ti (as Ti02) is added to a LiCo02 sample having preferred morphology. The
Ti02 - dry coated LiCo02 is heated at 1015°C in air, resulting in samples LC0315 & 316. Pellet
density did not increase. Samples of Example 1 or 4 have - at similar particle size -
significantly higher pellet density. Figures 9a and 9b show that the voltage profile is much
less rectangular than that of samples of Example 1 and 4. This Counterexample shows that Ti
needs to be finely dispersed within the precursor. If it is added on the outside of the sample
a much higher Ti doping is needed before a clear beneficial effect is observed.
Counterexample 7
This example shows that Ti doped LiCo02 - prepared from a standard precursor different
from the composite material of this patent - involves severe problems. The precursor is
C03O4, doped with 1 mol% magnesium per 1 mol cobalt, Li2C03 (same batch like used for all
other examples and counter examples, and Ti02 sub-micrometer powder (uncoated
pigment).
First a well-homogenized pre-blend containing a fraction of the Co304 and all Ti02 (the Ti02
is carefully pre-dried), is prepared, this blend is added to the remaining Co304 and Li2C03
and blending is continued. The final blend does not contain any visible agglomerates of Ti02
or Li2C03. The final blend contains 0.25 mol% Ti02 per 1 mol Co.
A total of 4 blends with Li:Co ratios ranging from 1.054 to 1.072 are used, firing at 1000°C
results in Ti + Mg doped LiCo02. The obtained particle size is significantly smaller (10-15 um)
than expected for similar Li:Co blend ratios without Ti02. As a comparison - using the same
Co304 precursor, the same firing conditions and the same Li:Co blend ratios yields particle
sizes ranging from 24 - 35 um. This shows that it is not possible to obtain a preferred
morphology (PSD of 15-20 um) without using excessive high Li:Co blend ratios or excessive
high sintering temperature.


The underlying mechanism is possibly the following: Ti02 is very efficient to prevent
sintering by inter particle sintering, as a result there is less growth of particle size. Thus - in
order to obtain Ti doped LiCo02 with preferred morphology - i.e. having larger and compact
particles requires that the Ti02 is finely dispersed within larger sized precursor particles, as
described in this invention.
Example 8
Figure 10 shows the pellet density as function of particle size D50. The samples on the upper
dotted line have Mg contents from 0 to 2 mol%, and Ti content of 0.25 mol56. The samples on
the lower dotted line have a Ti content of 0, 0.5 and 0.75 mol%, and 0.5 to 2 mol% Mg. No
sample without titanium has a sufficient high pellet density. Of the samples with high pellet
density only those with 0.25 mol% precursor doping have a preferred morphology. Example 8
clearly shows the benefit of titanium doping for obtaining increased pellet density.
Example 9
The large pool of samples with 0% Ti doping and O.25mol5£ Ti doping is analyzed in order to
understand how to prepare basically identical samples (morphology, PSD, lithium:Co ratio,
BET, .. ) mainly differing by Ti content only. Additionally, the Ti doped sample has a
significantly higher pellet density.


Full cells testing shows an clearly improved stability of the Ti doped sample during extended
cycling (> 500 cycles). The TiOz doped sample, compared with an undoped reference, shows
clearly less voltage depression (=unwanted impedance), especially at the beginning of
discharge. At the same time, the capacity fading rate is clearly improved. Figures 11a and b
illustrate this, for resp. Samples LCO 214 and 207.
While specific embodiments and/or details of the invention have been shown and described
above to illustrate the application of the principles of the invention, it is understood that
this invention may be embodied as more fully described in the claims, or as otherwise known
by those skilled in the art (including any and all equivalents), without departing from such
principles.

Claims
1. Precursor compound of a titanium doped lithium cobalt oxide powder for use as an active
positive electrode material in lithium-ton batteries, said precursor compound consisting of
either one or more of a non-sintered agglomerated cobalt oxide, hydroxide and oxy-
hydroxide powder having a secondary particle size with a d50 of more than 15 µm; said
agglomerated cobalt oxide, hydroxide and oxy-hydroxide powder comprising TiO2 in the form
of nanoparticles being homogeneously distributed within said agglomerated powder, with a
Ti content of between 0.1 and 0.25 mol%..
2. Precursor compound according to claim 1, characterized in that said
either one or more of a non-sintered agglomerated cobalt oxide, hydroxide and oxy-
hydroxide powder further comprises Mg as doping element with a Mg content between 0,1
and 2 mol%,
3. Precursor compound according to claim 2. characterized in that said either one or more
of a non-sintered agglomerated cobalt oxide, hydroxide and oxy-hydroxide powder further
comprises Ma as doping element with a Me content greater than 0.25 and UP to 2 mol%. and
preferably between 0.5 and 2 mol%.
4. Precursor compound according to any one of claims 1 to 3. characterized in that
said TiO2 nanoparticles have a size range of ≥ 5 nm and ≤ 200 nm, and preferably between
10 and 50 nm.
5. Use of a precursor compound according to any one of claims 1 to 4 in the
manufacture of a lithium cobalt oxide powder for use as an active positive electrode
material in lithium batteries, said lithium cobalt oxide powder having a Ti content of
between 0.1 and 0.25 mol%, by firing said precursor with a lithium source.
6. Use according to claim 45, wherein said lithium cobalt oxide powder has a d50 of more
than 10 µm, preferably more than 15 µm, and a specific surface area (BET) of less than 0.25
m2/g, and preferably 0.20 m2/g.
7. Single firing process for manufacturing a lithium cobalt oxide powder, comprising the
steps of;
- providing for a precursor compound according to any one of claims 1 to 4.
- mixing said precursor compound with a Li source, preferably lithium carbonate, according
to a Li to Co ratio R between 1.04 and 1.07, and

A precursor compound of a titanium
doped lithium cobalt oxide powder consists of
either one or more of a non-sintered agglomerated
cobalt oxide, hydroxide and oxy-hydroxide powder
having a secondary particle size with a d50 of
more than 15 µm; said agglomerated cobalt oxide,
hydroxide and oxy-hydroxide powder comprising
TiO2 in the form of nanoparticles being homogeneously
distributed within said agglomerated
powder, with a Ti content of between 0.1 and
0.25 mol%.