CA2510880A1 - Process for the preparation of a composite - Google Patents
Process for the preparation of a composite Download PDFInfo
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- CA2510880A1 CA2510880A1 CA002510880A CA2510880A CA2510880A1 CA 2510880 A1 CA2510880 A1 CA 2510880A1 CA 002510880 A CA002510880 A CA 002510880A CA 2510880 A CA2510880 A CA 2510880A CA 2510880 A1 CA2510880 A1 CA 2510880A1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/582—Halogenides
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Description
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 i , 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 i 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 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, 4 , 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.
E , 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 4 . , 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.
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 ,+
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 ., .. , 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 ., , 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 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 ,, , 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 ,. . ...
r 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.
...
w 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.
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:
.,..
. , 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:
..
,., ~ , .
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 ,. , 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.
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 i , 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 i 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 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, 4 , 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.
E , 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 4 . , 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.
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 ,+
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 ., .. , 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 ., , 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 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 ,, , 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 ,. . ...
r 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.
...
w 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.
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:
.,..
. , 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:
..
,., ~ , .
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 ,. , 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.
Claims (10)
1. Process 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:
.cndot. A is of the nominal formula AB(XO4)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% at. of the main +2 redox metals, including 0, XO4 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 XO4 oxyanion, including 0.
The above material are preferably phosphate-based and may have an ordered or modified olivine structure.
.cndot. or A is of the nominal formula Li3-x M' y M"2-y(XO4) 3 in which:
O.apprxeq.x < 3, O.apprxeq.y.apprxeq.2; M' and M" are the same or different metals, at least one of which being a redox transition metal; XO4 is mainly PO4 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.
.cndot. or A is of the nominal formula Li (Fe x M n1-x) PO4 in which 1 .apprxeq. x .apprxeqØ
.cndot. or A is of the general formula LiMPO4F with M is choose preferably, but not limited to, from Fe2+, V2+, Mn2+ or mixtures thereof.
.cndot. optionally A phase could also be doped by cation such as, but not limited to, Mo, W, Nb, Mg, Ni, Co, Cu, Al, Ti, Ge, Sn, Ca, V, Cr, Zn, Ta, In, and Mn.
.cndot.A' is one of the A formula, doped or undoped, with the proviso that A' .noteq. 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 Li2Mo2O7, Li2Mo3O10, Li2Mo4O13, Li2MoO4, MgMoO4, Ag2MoO4, Li2WO4, MnWO4, FeWO4, FeMoO4, Li2W2O6, W4O11, W2O5, WO3, Li2W5O15, Li2W4O12, Li2W3O9, LixWO3 and LixMoO3 (1 .apprxeq. × .apprxeq.0), derivatives of polymolybdate(VI), polytungstate(VI), polytantalate(V) and polynobiate(V)acids and more generally polyoxoanions.
with the proviso that process includes step of:
-providing a precursor of said micro-composite lithium-ion reversible electrode material, -heating said precursor, -melting same at a temperature sufficient to produce a melt comprising an oxyanion containing liquid phase, -cooling said melt under conditions to induce solidification thereof and obtain a solid electrode that is capable of reversible lithium ion deinsertion/insertion cycles for use in a lithium battery.
.cndot. A is of the nominal formula AB(XO4)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% at. of the main +2 redox metals, including 0, XO4 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 XO4 oxyanion, including 0.
The above material are preferably phosphate-based and may have an ordered or modified olivine structure.
.cndot. or A is of the nominal formula Li3-x M' y M"2-y(XO4) 3 in which:
O.apprxeq.x < 3, O.apprxeq.y.apprxeq.2; M' and M" are the same or different metals, at least one of which being a redox transition metal; XO4 is mainly PO4 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.
.cndot. or A is of the nominal formula Li (Fe x M n1-x) PO4 in which 1 .apprxeq. x .apprxeqØ
.cndot. or A is of the general formula LiMPO4F with M is choose preferably, but not limited to, from Fe2+, V2+, Mn2+ or mixtures thereof.
.cndot. optionally A phase could also be doped by cation such as, but not limited to, Mo, W, Nb, Mg, Ni, Co, Cu, Al, Ti, Ge, Sn, Ca, V, Cr, Zn, Ta, In, and Mn.
.cndot.A' is one of the A formula, doped or undoped, with the proviso that A' .noteq. 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 Li2Mo2O7, Li2Mo3O10, Li2Mo4O13, Li2MoO4, MgMoO4, Ag2MoO4, Li2WO4, MnWO4, FeWO4, FeMoO4, Li2W2O6, W4O11, W2O5, WO3, Li2W5O15, Li2W4O12, Li2W3O9, LixWO3 and LixMoO3 (1 .apprxeq. × .apprxeq.0), derivatives of polymolybdate(VI), polytungstate(VI), polytantalate(V) and polynobiate(V)acids and more generally polyoxoanions.
with the proviso that process includes step of:
-providing a precursor of said micro-composite lithium-ion reversible electrode material, -heating said precursor, -melting same at a temperature sufficient to produce a melt comprising an oxyanion containing liquid phase, -cooling said melt under conditions to induce solidification thereof and obtain a solid electrode that is capable of reversible lithium ion deinsertion/insertion cycles for use in a lithium battery.
2. Process according to claim 1, wherein said oxyanion-based lithium-ion reversible electrode material is phosphate base, and said melt comprises a phosphate containing liquid phase.
3. Process according to claim 1 wherein microstructure of micro-composite is control through annealing by slow cooling, cooling with thermal or quick cooling.
4. Process according to claim 1 where phase A' present an electronic conductivity of at least 10-6 ohm-1.cm-1.
5. Process according to claim 1 where A' phase is a W or Mo bronze phase LixMo03 or LixWO3, or mixture thereof.
6. Process according to claim 1 where A phase as a crystallite size < 1 micron.
7. Process according to claim 1 where A phase as a crystallite size < 100 nm.
8. Process according to claim 1 where A phase as a crystallite size < 10 nm.
9. Process according to claim 1 where powderized micro-composite is carbon coated.
10. Electrode for lithium batteries using a compound obtained from claim 1-9.
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| CA002510880A CA2510880A1 (en) | 2005-07-06 | 2005-07-06 | Process for the preparation of a composite |
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|---|---|---|---|
| CA002510880A CA2510880A1 (en) | 2005-07-06 | 2005-07-06 | Process for the preparation of a composite |
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