Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR PREPARING E?~ECTROACTIVE INSERTION COMPOUNDS AND EhECTRODE
MATERIALS OBTAINED THEREFROM
TECHNICAL FIE?~D
The invention relates to a process for preparing composite transition
metal oxyanions based electroactive compounds for battery application
and to materials made by said process, such as Li3Fe2 ( P04 ) 3/LiFeP09,
metallic bronze/LiFeP04 ceramic-ceramic composite and other analog
compounds for use in lithium batteries.
BACKGROUND ART:
Transition metal phosphate-based electrode materials for lithium
batteries and their synthesis.
Since Goodenough pointed out the value of lithium ion reversible iron
phosphate-based electrodes for use in lithium and lithium-ion
batteries (J. Electrochemical Society, vol. 144, No. 4, pp. 1188-1194
and US Pat. Nos. 5,810,382; 6,391,493 B1 and 6,514,640 B1) several
groups have developed synthesis processes for making lithiated iron
phosphates of the ordered-olivine, modified olivine or rhombohedral
nasicon structures and other chemical analogs containing transition
metals other that iron.
Until now most processes and materials described in the art to
manufacture electrochemically active phosphate-based electrodes for
use in battery applications are based on solid state reactions
obtained with iron+2 precursors intimately mixed with lithium and
phosphate containing chemicals that are used individually or as a
combination thereof. Iron+2 oxalate and acetate are the more
frequently used starting materials for syntheses carried out under an
inert or partially reducing atmosphere to avoid transition metal
oxidation to a higher level, e.g. Fe+3 for example (see Sony PCT WO
00/60680A1 and Sony PCT WO 00/60679 Al). LiFeP04 active cathode
materials with improved electrochemical performance were also
obtained using C introduced as an organic precursor during material
synthesis (Canadian Application No. 2,307,119, laid-open date October
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30, 2000). Addition of carbon powder or C-coating to LiFeP04
increases powder electronic conductivity, normally in the range of
10-9-10-1° S.crri 1 for pure LiFeP09 at ambient temperature. More
recently, solid-state syntheses of LiFeP04 obtained from Fe+3
precursors such as Fe203 or FeP04 have been described. These syntheses
use reducing gases or precursors (PTC/CA2001/001350 published as WO
02/27824 and PTC/CA2001/001349 published as WO 02/27823) or are
carried out by direct reduction (so-called carbothermic reduction) of
mixed raw chemicals with dispersed C powder (Valence PCT WO 01/54212
A1).
All of these solid-state synthesis reaction ways require relatively
long reaction time (several hours) and intimate mechanical dispersion
of reactants since the synthesis and/or particle growth in the solid
state are characterized by relatively slow diffusion coefficients.
Furthermore, particle size, growth, and particle size distribution of
the final electrode material are somewhat difficult to control from
chemical precursors particle dimensions or in view of the reactive-
sintering process, partially suppressed by the presence of dispersed
or coated carbon on reacting materials.
Recent attempts to grow pure or doped LiFeP04 in solid state and at
high temperature, for example 850°C, have led to iron phosphate with
20 micron single grain sized, intimately mixed with iron phosphide
impurities and with elemental C thus making intrinsic conductivity
evaluation difficult (Electrochemical and Solid-State Letters, 6,
(12), A278-A282, 2003).
Recently, a process to obtain pure crystalline LiFeP04 from melt has
been described by fusion under inert gas of iron, phosphate and
lithium precursor such as Fe0/P205/LiOH at 1500°C (New Simple
Syntheses of Amorphous and Crystalline Iron Phosphate Cathodes,
S. Okada, Y. Okazaki, T. Yamamoto, J.-I. Yamaki, and T. Nishida,
206th ECS Meeting, Oct. 3-8, 2004, Honululu).
To overcome slow insertion kinetics of LiFeP04, several solutions
have been considered such as carbon-coated LiFeP04 and/or doping with
cations (See US 6,514,640, US 2002/106564, US 2002/124386). However,
in most case effect of doping is not clearly asserts as synthesis
process could induce formation of carbon deposit inducing improve
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surface conductivity.
In view to improve usage value of phosphate based insertion compounds
such as LiFeP04, inventors after intensive R&D, designed micro-
composite compounds with the aim to prepare insertion compounds such
as LiFeP04 intimately mixed with higher ionic conductivity and/or
electronic conductivity. None of the previously demonstrated
synthesis procedures to make LiFeP04 suggest possible synthesis of
such micro-composite insertion compounds and even less through melt
process.
DISCLOSURE OF THE INVENTION:
New process for making micro-composite lithiated transition metal
phosphate cathodes
The present invention relates to a new process based on the use of a
molten phase, preferably a molten phosphate-containing liquid phase,
to obtain micro-composite lithiated or partially lithiated transition
metal oxyanion-based, such as phosphate-based, electrode materials.
The process comprises the steps of providing precursors of the
lithium-ion reversible electrode material, heating the electrode
material precursors, produce by thermal treatment a melt comprising
an oxyanion, such as phosphate, containing liquid phase, and cooling
the melt under conditions to induce solidification thereof, and
obtain a micro-composite solid electrode material that is capable of
reversible lithium ion deinsertion/insertion cycles for use in a
lithium battery. Any one of these steps may be carried out under a
non-reactive or partially reducing atmosphere. According to a
preferred embodiment, the process may include chemically reacting the
precursors when heating and/or melting same.
As used in the present description and claims, the term precursor
means an already synthesized at least partially lithiated transition
metal oxyanion, preferably phosphate, electrode material or naturally
occurring lithiated transition metal oxyanion, preferably phosphate
minerals, such as triphylite, having the desired nominal formulation
or, a mixture of chemical reactants containing all chemical elements
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required for making, when reacted, an at least partially micro-
composite lithiated transition metal oxyanion, such as phosphate-
based, electrode material of the right formulation. The mixture may
contain other metal and non-metal element additives or reductant
chemicals such as C or other carbonaceous chemicals or metallic iron,
or mixtures thereof.
According to a preferred embodiment of the invention, the temperature
at which the molten phosphate containing phase is obtained, is
between the melting point of the micro-composite lithiated transition
metal phosphate material and 300°C above, more preferably less that
150°C above that temperature, in order to limit thermal decomposition
or further reduction of the reactants or final product in the
presence of reducing chemicals, such as C or gases. Another
advantage of limiting the temperature above the melting temperature
of the final product is to avoid energy cost and higher cost of
furnace equipment when the temperature exceeds 1200°C.
According to another embodiment of the invention, the
temperature at which the molten phosphate containing phase is
obtained, is between a fixed temperature between 300°C above the
melting point of the micro-composite lithiated transition metal
phosphate material and 200°C, more preferably 100°C under that
melting point, in which case the final micro-composite lithiated
transition metal phosphate is solidified from the melt upon cooling.
The process according to the invention may also be used for
preparing a micro-composite lithiated or partially lithiated
transition metal oxyanion-based electrode materials composed of at
least two phases A/A' in which:
~A is of the nominal formula AB(X04)H, in which
A is lithium, which may be partially substituted by another
alkali metal representing less that 20~ at. of the A metals,
B is a main redox transition metal at the oxidation level of +2
chosen among Fe, Mn, Ni or mixtures thereof, which may be partially
substituted by one or more additional metal at oxidation levels
between +1 and +5 and representing less than 35°s at. of the main +2
redox metals, including 0,
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X04 is any oxyanion in which X is either P, S, V, Si, Nb, Mo or
a combination thereof,
H is a fluoride, hydroxide or chloride anion representing less
that 35~ at. of the X04 oxyanion, including 0.
The above material are preferably phosphate-based and may have
an ordered or modified olivine structure.
~or A is of the nominal formula Li3-XM' yM"2-y (X04) 3 in which: O~x<3,
O~y~2; M' and M" are the same or different metals, at least one of
which being a redox transition metal; X04 is mainly P04 which may be
partially substitued with another oxyanion, in which X is either P,
S, V, Si, Nb, Mo or a combination thereof. The electrode material
preferably has the characteristics of the rhombohedral Nasicon
structure.
~or A is of the nominal formula Li (FeXMnl_X) P04 in which 1 ~ x ~0.
~or A is of the general formula LiMP04F with M is choose preferably,
but not limited to, from Fez+, V2+, Mn2+ or mixtures thereof .
~optionally A phase could also be doped by cation such as, but not
limited to, Mo, W, Nb, Mg, Ni, Co, Cu, A1, Ti, Ge, Sn, Ca, V, Cr, Zn,
Ta, In, and Mn.
~A' is one of the A formula, doped or undoped, with the proviso that
A' x A. A' could also be choose among Mo, W, Ta and Nb oxides
including bronze form, heteropoly blues, blue oxides,
heteropolyanions as described in Cotton and Wilkinson, Advanced
Inorganic Chemistry (5th edition) p 808-811 and in Pascal, Nouveau
Traite de Chimie Minerale, Tome XIV p 553-904, such as Li2Mo207,
Li2Mo3010, Li2Mo4013, Li2Mo04, MgMo04, Ag2Mo04, Li2W04, MnW04, FeW04,
FeMo04, Li2W206, W4011, W205, W03, Li2W5015, Li2W4012, Li2W309,
LixW03 and LixMo03 (1 ~ x ~0), derivatives of polymolybdate(VI),
polytungstate(VI), polytantalate(V) and polynobiate(V)acids and more
generally polyoxoanions.
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As used in the present description and claims, the term "nominal
formula" refers to the fact that the relative ratio of atomic species
may vary slightly, in the order of 0.1o to 5% and more typically from
0.5o to 2o, as confirmed by a common general XRD pattern and by
chemical analysis.
The process according to the invention can provide micro-composite
lithiated or partially lithiated transition metal phosphate-based
electrode materials that have a partially non-stoichiometric nominal
formula, provide solid solutions of the transition metal or of the
oxyanion, or slightly doped nominal formula with improved electronic
conductivity, and optionally improved ion-diffusion characteristics.
The term "improved electronic conductivity" as used in the present
description and claims means, in the case of micro-composite
containing LiFeP09, the improved capacity of the cathode material to
conduct electricity by more than one order of magnitude as compared
to the conductivity of LiFeP04 obtained by a solid-state synthesis
reaction without using any electronic conductivity additive or a
phosphate capable of dissipating a charge under SEM observation
(without in this case the use of any C or other electronically
conductive coating additive, SEM observation that cannot be achieved
with pure stoichiometric LiFeP04 material with no conductivity
additive for example).
The invention provides a new synthesis process based on the
use of a molten phase, preferably a molten phosphate-rich phase, to
make micro-composite lithiated or partially lithiated transition
metal phosphate-based electrode materials, wherein the micro-
composite lithiated or partially lithiated transition metal
phosphate-based electrode formulations are preferred, first because
they are well suited for use in lithium batteries assembled in their
discharged (lithiated) state, second, because a lithiated (reduced)
electrode formulation allows greater thermal stability to some
phosphate crystal structure and also to their corresponding molten
form.
According to a preferred embodiment of the present invention,
the molten phase comprises at least the cathode material in its
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molten state before solidification and is obtained by chemically
reacting the precursor during the heating or melting steps or simply
by melting the precursor which in this case already comprises the at
least partially lithiated transition metal phosphate based cathode
material.
According to another preferred embodiment of the invention,
the atmosphere used during at least the steps of heating and melting
is a partially reductive atmosphere. By partially reductive
atmosphere, we refer to the fact that the atmosphere comprises gases
such as C0, H2, NH3. HC and also C02, N2, and other inert gases in a
proportion and at temperature selected so as to bring or maintained
the redox transition metal at a fixed oxidation level, for example +2
in the AB (X04 ) H coumpounds, without being reductive enough to reduce
said redox transition metal to metallic state. By HC we mean any
hydrocarbon or carbonaceous product in gas or vapor form.
In the present description and claims, the term "redox
transition metal" means a transition metal that is capable of having
more than one oxidation state higher than 0, e.g. Fe+2 and Fe+3, in
order to act as an electrode material by reduction/oxidation cycle
during battery operation.
According to another embodiment of the invention, an inert or
non reactive atmosphere is used and only the thermal conditions and
the presence of lithium in the molten transition metal based
phosphate phase is used to stabilize the redox transition metal in
its desired oxidation state, e.g. Fe+2 in the case of LiFeP04 bases
micro-composite.
Another preferred embodiment of the invention is
characterized the presence of C or a solid, liquid or gaseous
carbonaceous material during at least one of the steps of heating,
optionally reacting, and melting, optionally reacting, the electrode
precursor. Said C should be chemically inert or compatible (low
reactivity) with reaction products during the synthesis, optionally
it should be capable of trapping ingress of oxygen traces to keep the
redox transition metal in its oxidation state of +2 or in some cases
capable of partially or totally reducing the redox transition metal
to its oxidation state of +2.
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Another preferred embodiment of the invention is
characterized by the fact that one or more solid-liquid or liquid-
liquid phase separations occur during the melting step thus allowing
separation and purification of the molten cathode material from other
impurities including C powder, Fe2P, unreacted solids or other solids
or liquid non miscible phases, that are present in other phases non-
miscible with the liquid molten cathode material. Alternatively, the
invention allows for separation and purification during the cooling
step where impurities or decomposition products that are soluble in
the molten phase can be rejected during the cooling and
crystallization step.
According to the process of the invention doping or substitution
elements, additives, metals, metalloids, halides, other complex
oxyanions (X04), and oxide-oxyanions (0-X04) systems, where X may be
non limitatively Si, V, S, Mo and Nb can be incorporated with the
cathode material formulation during the heating, and/or reacting
steps or, preferably, while the lithiated transition metal phosphate-
based electrode material is in molten state. Examples of doped, non-
stoechiometric or partially substituted formulations contemplated by
the present invention include but are not limited to those disclosed
in US 6,514,640 B1. Other doping effects resulting, for example, from
the partial solubility of products resulting from the thermal
decomposition of the phosphate electrode precursor are also included
in the process and materials of the present invention.
According to another embodiment of the invention, the cooling
and solidification step is rapid in order to quench the liquid phase
and obtain otherwise metastable non-stoichiometric electrode
formulation or doped compositions.
Another of the materials obtained with the process of the
invention is the fact that they have intrinsic electronic conducting
properties, optionnally ionically enhanced Li+ ion diffusion
properties while having pure nominal formulation, possibly but not
limitatively as a result of some degree of non-stoichiometry with
some lithium and transition metal site reciprocal substitution.
Another preferred embodiment of the invention is based on the
controlled cooling and crystallization of the molten lithiated
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transition metal phosphate phase also containing other additives or
impurities in order to precipitate such additive or impurities during
crystallization or other subsequent thermal treatment in order to
make an intimately mixed composite material made of crystallites of
the lithiated transition metal phosphate cathode material intermixed
with at least another phase containing additive or impurities, said
phase having electronic or Li+ ion diffusion enhancing properties
when the composite material is used as an Li-ion reversible
electrode.
According to another preferred embodiment of the invention
the electrode precursor material comprises a mixture of chemicals
containing all elements required and selected to react chemically to
give essentially the phosphate-based cathode formulation while in the
liquid state. Preferably the chemical used for the electrode
precursor are low cost, largely available commodity materials or
naturally occurring chemicals including in the case of LiFeP04, iron,
iron oxides, phosphate minerals and commodity lithium or phosphate
chemicals such as: Li2CO3, LiOH, P205, H3P04, ammonium or lithium
hydrogenated phosphates. Alternatively the chemical are combined or
partially combined together to facilitate the synthesis reaction
during the heating or melting steps. Carbonaceous additive, gases or
simply thermal conditions are used to control the redox transition
metal oxidation level in the final lithiated product.
In another embodiment, the process is characterized by the
fact that the molten process is carried out in the presence of a C
crucible and lid and uses an inert or slightly reductive atmosphere
at a temperature ranging preferably between 700 and 1200°C, more
preferably between 900 and 1100°C. Alternatively a somewhat lower
temperature can be used if a melting additive is used during the
heating and/or melting steps. By melting additive one means low
temperature melting phosphate chemicals (e.g. P205, LiH2P0a. Li3P04,
NH9H2P04, Li4P207, for example) or other low temperature melting
additive, LiCl, LiF, LiOH that may contributes to the final
phosphate-based electrode formulation during the melting step or
after the cooling step.
One important alternative of the invention is characterized
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by the fact that redox transition metal can be kept at a its lower,
lithiated or partially lithiated discharged state during the heating,
optionally including a reacting step and during the melting,
optionally including a reacting step without any reductant additive,
such as C, and under an inert atmosphere by the sole use of a heating
and melting temperature high enough to insure thermal stability or
reduction of the redox metal at the lower discharged state in a
chemical formulation stabilized by the presence of lithium ion. Some
embodiments of the invention confirm the fact that LiFeP09 or
Li(FeMn)P04 mixtures for example can be synthetized and/or melted
indifferently from a Fe+z, from a Fe+2/Fe+3 mixture, from a Fe°/Fe+3
mixture or a purely Fe+3 containing precursor, and this without C or
other reductive additives or atmospheres.
Advantages of the invention:
Some of the advantages of a process (and material so obtained)
based on the melting of a lithiated or partially lithiated redox
transition metal oxyanion, such as phosphate-based formulation and of
the electrode materials obtained thereby will appear from the
following examples of the present invention.
To one skilled in the art, a molten-phase manufacturing process
offers the possibility of a rapid and low cost process to synthesize
or transform phosphate based electrode materials as opposed to a
solid-state synthesis and/or a sintering reaction. Furthermore,
chemically combining the precursor components before and especially
during the melting step allows for a direct melt-assisted synthesis
from a large range of available commodity chemicals, including
naturally occurring minerals as starting reactants.
Despite the fact that the melting step is usually carried out at
relatively high temperature, for example between 900-1000°, the
process allows a solid-liquid or liquid-liquid phase separation that
contributes to lithiated transition metal phosphate-based electrode
material purification when the precursor is already a crude lithiated
transition metal phosphate-based made by synthesizing chemical
elements that form an impure liquid phase of the lithated transition
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metal phosphate material. All means of heating known to the
specialist are contemplated by the present invention including
combustion, resistive and inductive heating means applicable to a
large batch or to a continuous process.
The process can be carried out in the presence of C or other
reducing additives or atmospheres or without any reducing agent, by
simply selecting the temperature at which the electrode material is
heated and melted thus allowing different conditions for preparing
different lithiated phosphate-based electrode materials with
different redox metals and different defective or doped crystal
structures.
The melting and cooling steps result in electrode materials of a
relatively high particle top density form in a range of different
particle sizes and distributions as obtained by grinding, sieving and
classifiying by means known in the battery, paint or ceramic art.
Furthermore, pure, doped, or partially substituted electrode
material of complex formulations can be made easily and rapidly
through solubilization of the additive elements in the molten phase,
which are thereafter cooled and solidified in their crystalline form
to expel partially or totally the additives from the crystal
structure or, alternatively, in their amorphous or crystal defective
form by rapid quenching for example in order to optimize electronic
conductivity or Li-ion diffusion. A preferred mode of realization is
take advantage of thermal treatment of additive solubility in the
molten phase to form doped electrode material containing the
lithiated transition metal phosphate-based electrode material and/or
or composite material with a separate phase containing part or
totality of the additive. Such doped or composite electrode material
having improved electronic conductivity or improved Li-ion
diffusivity.
The process of the invention also allows reprocessing or
purifying of synthetic lithiated or partially lithiated transition
metal phosphate-based electrode materials or alternatively of
lithiated transition metal phosphate natural ores at any steps of the
heating/melting/cooling process.
Another characteristic of the invention is to allow ease of
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control of the particle size and distribution by first melting, then
cooling dense phosphate-based electrode materials followed by any of
appropriate conventional crushing, grinding, jet milling/classifying
/mecanofusion techniques. Typical particle or agglomerate sized that
are available to one skilled in the art range between hundredth or
tenth of a micron to several microns.
Since the process allows to synthesize a pure electrode
material, especially without C, any ulterior C coating or addition
independently of the synthesis process as well as any other surface
treatment known to one skilled in the art becomes easy to make and
control.
A process based on a molten step allows major process
simplifications versus other known solid state processes for making
phosphate-based cathode materials since the molten process of the
invention allows the use of mixtures of largely available raw
chemicals or even of natural minerals as well as of pre-synthetised
electrode materials as precursor. Presently, known solid state
reaction processes require intimate mixing of the reactant powders
and relatively long residence time for the synthesis reaction to be
completed. On the contrary, a molten phase at high temperature allows
rapid mixture and synthesis reaction as well as the introduction of
additives, substitution elements and dopants in the molten state.
More specifically the molten state facilitates the manufacture
of optimized, doped, partially or totally substituted lithiated or
partially lithiated phosphate cathode materials containing other
metal, halide or oxyanions (X04) or oxide-oxyanion other that pure
phosphates.
One very important characteristic of the process of the
invention is that it was found possible to obtain an electrode
material of improved electrical conductivity and possibly of greater
Li-ion diffusivity, for example intrinsically electronic conductive
LiFeP04 was obtained with the process of the invention, i.e. without
doping LiFeP04 with other elements than Li, Fe, P and 0. Most
probably but without limitation, this is the result of an off-
stoichiometric composition and/or reciprocal ion site substitution.
Similarly, phosphate-based electrode formulations such as
r
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Li (FeMn) P04, LiFe~o.9>Mgco.mPOQ or doped LiFeP09 were prepared according
to the present invention to allow for an optimization of electronic
conductivity and high Li-ion diffusion. In addition to the fact that
the present invention allows to use less costly Fe precursors (Fe,
Fe203, Fe304, FeP04 instead of Fe+2 phosphates, acetate, oxalates,
citrates, etc), the invention also makes it possible to design new
structures not available by other solid-state process, e.g., liquid-
phase solubilization, substitution and doping followed by quenching
or thermal treatment to achieve controlled crystallization or
precipitation among others.
Another particularity of the invention is that it offers the
possibility to use less pure precursors such as FeP04 or LiFeP04 with
larger stoechiometry ratio window and/or with any Fe3+/Fe2+ ratio
since the phase separation in the molten state combined with the
heating and melting step temperature can correct stoichiometry,
formulation in combination or not with cooling solidification
process.
Depending on the redox metals used for the lithiated or
partially lithiated phosphate-based formulations, the invention
offers the possibility to work under normal air, or in the case of
iron containing material, just by using a C container and C lid and
simply limiting exposition to air during the heating, melting and
cooling steps of the process.
The process of the invention encompass the possibility to
prepared inorganic-inorganic composite based on the use of a molten
phase that might comprise impurities or additive soluble only in the
molten state, more that one liquid molten phase or that might
comprise an additional solid phase co-existing with the molten phase
thus resulting upon cooling in a composite system containing the
solid transition metal phosphate-based electrode material lithiated
or partially lithiated and intimately mixed with another solid phase
having beneficial electronically or ionically conducting
characteristics as an electrode material. . Interesting
electrochemical results have been achieved also using Cr and
especially Mo additive in order to create doped or composite
electrode materials made of more or less doped LiFeP04 with a Mo
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containing phase excluded from the LiFeP04 structure during thermal
cooling from the molten state.
Another aspect of the invention is to be able to control morphology
of micro-composite by annealing materials through for example slow
cooling, cooling with step at temperatures allowing control
crystallisation and/or fine microstructure, or by rapid cooling. By
this way it is possible to produce micro-composite with enhanced
properties, especially in terms of power density and low temperatures
performances.
...
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Having generally described this invention a further understanding can
be obtained by reference to certain specific examples which are
provided herein for purposes of illustration only and are not
intended to be limiting unless otherwise specified.
EXAMPLES
Example 1: Preparation of LiFeP04/Li3Fe2(PO9)3 micro-composite:
LiFeP04 and Li3Fe2(P04)3 have been respectively prepared as described
in US 5910382 and in Journal of Solid State Chemistry, 135, 228-234
(1998). 0.1 mole of each have been then thoroughly crushed in an
agate mortar. This mix was then placed in an argon sealed quartz
ampule and heated at 1000°C during ~ 10-15 mn and then cooled in air.
Ceramic has been identified by XRD as a LiFeP09/Li3Fe2(PO9)3 micro-
composite. A similar experiment has been performed with Mn doped
compounds (Fe:Mn 9:1) to produced a Mn doped LiFeP04/Li3Fe2(P04)s
micro-composite.
Example 2: Preparation of LiFeP04/Li3Fe2(P04)3 micro-composite:
LiFeP04 and Li3Fe2 (P04) 3, prepared as in example 1, have been
thoroughly crushed in an agate mortar in various molar ratio
(LiFeP04/Li3Fe2 (P04) 3: 4/1, 3/2, 2/3 and 1/4) . Those mixes were then
placed in argon sealed quartz ampules and heated at 1000°C during
10-15 mn and then cooled in air. Ceramics have been identified by
XRD as LiFeP04/Li3Fe2(P04)3 micro-composites with LiFeP09/Li3Fe2(PO9)s
ratio increasing as LiFeP04 ratio in the mix prior to thermal
treatment.
Example 3: Preparation of LiFeP04/Li3Fe2(P04)3 micro-composite:
FeP04~2H20 (37.37 g) and LiZC03 (7.39 gr) were thoroughly mixed in an
agate mortar. This mixed was then placed in an alumina ceramic
crucible and heated in an airtight oven under a flow of CO/C02 (3:1)
from ambient temperatures to 980°C ~ 5°C in ~ 100 minutes,
maintained
at 980°C ~ 5°C during ~ 60 mn and then cooled to ~ 50°C
in ~ 3 hours.
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Ceramic have been identified by XRD as LiFeP04/Li3Fe2(P04)3 micro-
composite.
Example 4: Preparation of LiFeP09/Li3Fe2(P04)3 micro-composite:
Fe203 (0.1 mole), Li2C03 (0.1 mole) and diammonium phosphate
(0.02 mole) were thoroughly mixed in an agate mortar. This mixed was
then placed in an alumina ceramic crucible and heated in an airtight
oven under a flow of argon from ambient temperatures to 980°C ~
5°C
in ~ 100 minutes, maintained at 980°C ~ 5°C during ~ 60 mn and
then
cooled to ~ 50 ° C in ~ 3 hours . Ceramics have been identified by XRD
as LiFeP09/Li3Fe2(P04)3 micro-composite.
Example 5: Electrochemical characterization:
Electrochemical characterization of the ceramics product of example
1-4 was made to confirm the performance of the process of the
invention. Typically, ~ 2 g of ceramic was thoroughly crushed and
grinded in an agate mortar. Then, a cathode coating slurry was
prepared by thoroughly mixing with acetonitrile, ceramic (101.3 mg),
polyethylene oxide (product of Aldrich; 82.7 mg), 400,000 molecular
weight, and Ketjenblack (product of Akzo-Nobel; 16.7 mg) carbon
powder. This slurry was coated on a stainless steel support of
1.539 cm2 area whose composition is: 41~ wt. polyethylene oxide,
7.46°s wt. Ketjenblack and 51.54°s wt. ceramic. A button type
battery
has been assembled and sealed in a glove box using a 1.97 mg active
material cathode loading (1.28 mg/cm2, 0.78 C/cm2), a polyethylene
oxide 5.106 (product of Aldrich) containing 30~ wt. LiTFSI (product
of 3M) electrolyte and a lithium foil as anode. The battery was then
tested with a VMP2 multichannel potensiostat (product of Bio-Logic -
Science Instruments) at 80°C with a 20 mV/hr scan speed, between a
voltage of 1.7 V and 3.7 V vs Li+/Li°. Electrochemical response were
characteristics of both LiFeP04 and Li3Fe2(PO9)3 structures.
Example 6: Preparation of LiFeP04/W rich phase micro-composite:
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FeP04~2H20 (product of Chemische Fabrik Budenheim KG; 373.7 g), Li2C03
(product of Limtech; 71.7 g) and W03 (product of Aldrich; 13.9 g)
were thoroughly mixed in a mortar. This mixture was then placed into
a 400 oz graphite crucible and heated in an airtight oven under a
flow of argon from ambient temperatures to 980°C ~ 5°C in
100 minutes, maintained at 980°C ~ 5°C during ~ 60 mn and then
cooled to ~ 50°C in ~ 3 hours. Ceramics have been identified by XRD
as LiFeP04/W rich phase micro-composite. A similar experiment has
been performed replacing W03 by Mo03 to produce a LiFeP04/Mo rich
phase micro-composite. A similar experiment has been performed
replacing la mol Li2C03 by MgC03 to produce a Mg doped LiFeP04/Mo rich
phase micro-composite.
Example 7: Preparation of LiMnP04/Mo rich phase micro-composite:
Mn02 (product of Aldrich; 173.9 g), LiH2P04 (product of Limtech;
207.9 g) and Mo03 (product of Aldrich; 8.6 g) were thoroughly mixed
in a mortar. This mixture was then placed into a 400 oz graphite
crucible and heated in an airtight oven under a flow of argon from
ambient temperatures to 980°C ~ 5°C in ~ 100 minutes, maintained
at
980°C ~ 5°C during ~ 60 mn and then cooled to ~ 50°C in ~
3 hours.
Ceramics have been identified by XRD as LiMnP04/Mo rich phase micro-
composite.
Example 8: Preparation of LiFeP04/(W,Mo) rich phase micro-composite:
FeP04~2Hz0 (product of Chemische Fabrik Budenheim KG; 373.7 g), Li2C03
(product of Limtech; 71.7 g), Mo03 (product of Aldrich; 4.3 g) and
W03 (product of Aldrich; 7 g) were thoroughly mixed in a mortar. This
mixture was then placed into a 400 oz graphite crucible and heated in
an airtight oven under a flow of argon from ambient temperatures to
980°C ~ 5°C in ~ 100 minutes, maintained at 980°C ~
5°C during
60 mn and then cooled to ~ 50°C in ~ 3 hours. Ceramics have been
identified by XRD as LiFeP04/(W,Mo) rich phase micro-composite.
Example 9: Preparation of (Fe,V) Nasicon/Olivine micro-composite:
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LiFeP04 and Li3V2 (P04) 3 have been prepared respectively as described
in US 5910382 and EP 01252093 Bl. 0.1 mole of each have been then
thoroughly crushed in an agate mortar. This mix was then placed in an
argon sealed quartz ampule and heated at 1000°C during ~ 10-15 mn and
then cooled in air. Ceramic has been identified by XRD as a
Li(Fe,V)P04/Li3(Fe,V)2(P04)3 micro-composite. A similar experiment has
been performed with LiVP04F (prepared as in US 6855462) instead of
Li3V2 ( PO9 ) 3 to produce a Li ( Fe, V) PO~/Li ( Fe, V ) PO9F micro-composite
.
Example 10: Annealing of micro-composite:
Samples of LiFeP04/Mo rich phase micro-composite have been placed in
argon sealed ampules and heated at 1000°C during ~ 10-15 mn and then
cooled respectively at 1, 2, 5, 10 and 20°C/mn speed down to
600°C
and then cool in air down to ambient temperatures. Ceramics have been
identified by XRD as LiFeP09/Mo rich phase micro-composite. MEB
observation of annealed samples puts in evidence that annealing
allows to control morphology of micro-composite. Similar experiments
have been performed with LiFePO~/W rich phase, LiFeP04/(Mo,W) rich
phase and LiFeP04/Li3Fe2(P04)3 micro-composite, in both cases MEB
experiments also confirms that annealing allows to control
morphologies of those micro-composites.
Example 11: Electrochemical characterization:
g of each annealed LiFePOq/Mo rich phase prepared in example 10
were thoroughly crushed and grinded in an agate mortar. Subsequently
powders were C-coated using an organic C-precursor:
1,4,5,8-naphthalenetetracarboxylic dianhydride treatment as described
by Marca M. Doeff et al (Electrochemical and Solid-State Letters,
6(10) A207-209 (2003)). Thus, micro-composite powders (3.19 g) were
grinded in a mortar with 1,4,5,8-naphthalenetetracarboxylic
dianhydride (0.32 g; product of Aldrich) and 10 ml acetone. After
evaporation of acetone, the mixed were heated under a CO/COz (50~
volume of each gas) flow in a rotary chamber placed in an oven. The
,. ,
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chamber was first air evacuated by flowing CO/COz during 20 mn at
ambient temperature, heated to 650°C ~ 5°C in 100 mn and
maintained
at this temperature for 60 mn and then cooled to ambient temperature.
This process gave carbon coated grades of micro-composite powders
with a ~ 0.5o wt. C-coating (LECO). Lithium batteries were then
prepared as described in example 5. Ragone plot for each samples
indicates that annealing could improve properties of insertion
compounds through optimal microstructure of LiFeP04/Mo rich phase
induce by reducing crystallite size and efficient electronic
conductive pathways link to Mo rich phase presence.
Example 12: Preparation of LiFeP04/Li3Fe2(P04)3 micro-composite:
LiFeP09 and Li3Fe2 (P04) 3, prepared as in example 1, have been
thoroughly crushed in an agate mortar in various molar ratio
(Li3Fe2 (P04) 3: 1, 2, 3, 4 and 5% wt. of total) . Those mixes were then
placed in argon sealed quartz ampules and heated at 1000°C during
10-15 mn and then cooled in air. After have been C coated, lithium
batteries containing those samples have been prepared as in example
11. A comparative battery has been built with pure C coated LiFeP09.
Ragone plot for each samples indicates that LiFePOn/Li3Fe2(P04)3
present better power capabilities than pure LiFeP09 and that an
optimum between energy density and power density is obtained for
LiFeP04/Li3Fe2(P04)3 micro-composite containing 3% wt. Li3Fe2(P04)3.
Although the present invention has been described hereinabove by way of
preferred embodiments thereof, it can be modified, without departing
from the spirit and nature of the subject invention as defined in the
appended claims.
