Reactant iron source of defined and reproducible chemical composition and rapid kinetic

Abstract

A process for preparing a reactant iron source for use in the preparation of cathode materials. The reactant iron source has a general formula FeO1+x in which x varies between 0.046 and 0.195 ('FeO'). The process comprises treatment of a first iron source under controlled temperature (T) and oxygen partial pressure (pO2) to yield the reactant iron source having a defined and reproducible chemical composition and a rapid kinetic.

Description

TITLE OF THE INVENTIONREACTANT IRON SOURCE OF DEFINED AND REPRODUCIBLE CHEMICAL COMPOSITION AND RAPID KINETICFIELD OF THE INVENTION

[0001] The present invention relates generally to reactant iron sources and their use in the preparation of cathode materials. More specifically, the invention relates to a reactant iron source of general formula FeOi+xin which x varies between 0.046 and 0.195 (‘FeO’). The reactant iron source according to the invention (‘FeO’) has a defined and reproducible chemical composition and a rapid kinetic and can be used as single iron source in the preparation of a cathode material.BACKGROUND OF THE INVENTION

[0002] Since Lithium Iron Phosphate (LFP) and its analog Lithium Manganese Iron Phosphate (LMFP) were introduced and recently used as cathode materials for lithium batteries, several synthesis processes have been proposed. These processes rely on the use of several potential iron precursors: Fe3(PO4)2, Fe2Os, Fe2P2O?, FePO4, FeC2O4, and FeSO4 xH2O, with FePO4being the most widely used in solid-state processes, initially described in WO 02 / 27823 and WO 02 / 27824 and now mostly produced in China. The reason for its success comes from its apparent simplicity (simultaneous LFP synthesis and carbon coating) and a shorter dwell time, since combining slow diffusion Fe3+and PO43' ions in a single molecule. However, this solid-state process, like most other such processes, calls for pure chemical precursors whose synthesis is complex and multi-steps, resulting in waste products formation and / or with a need for large amount of water. This results in a monetary and / or environmental cost (wastes rejected e.g., Na2SO4) not favorable to large-scale energy storage and electric transport development especially in countries where environmental regulations are strict.

[0003] A high temperature molten synthesis process, recently developed, addresses these problems, and is described in the following related patent applications: WO 2005 / 062404 A1 , WO 2013 / 177671 A1 , and WO 2015 / 179972 A1 . The process described in these applications is much less reactant specific than previous processes, since it is conducted at high temperature in a liquid state where the reactions are rapid, and more importantly, since thermodynamic equilibrium can be obtained rapidly in conditions favorable to yield a well-defined LFP composition in the melt and once cooled and solidified.

[0004] The inventions described in these applications provide great simplification and cost reduction as to the reactants that can be used as Fe, Li, and PO4sources. For example, instead of using FePO4and a battery-grade Li2CO3in the solid-state process to make LFP as per WO 02 / 27823 and WO 02 / 27824, it was shown possible to use LiPO3or in-situ- formed LiPO3precursor and a simple mixture of Fe° and Fe2O3or Fe° and Fe3O4of a composition equivalent to FeO as per the overall reaction:(T and p0)3 LiPO3+(Fe0+Fe2O3) - - 3 LiFePO4Eq. 1

[0005] Such a dual source of Fe is needed, since Wustite (FeO) as such is not commercially available, nor considered stable at ambient temperature and neither a well- defined composition. Wustite is not a stoichiometric composition as such, since usually iron is defective and exists over a composition range. In contrast, iron metal (Fe°), hematite (Fe2O3), and up to a point magnetite (Fe3O4), are commercially available with well-defined compositions. LiPO3can be formed in-situ in the melt from Li-bearing precursors such as Li2CO3, LiOH, and Li2SO4, and P-bearing precursors such as P2Os, H3PO4, HPO3, Monohydrogen Ammonium Phosphate (MAP), and Dihydrogen Ammonium Phosphate (DAP), or Li- and P-bearing chemicals such as LiH2PO4and Li3PO4.

[0006] The use of Fe2O3and Fe3O4is interesting, since these high purity materials are widely available as pigments or specialty chemicals at a lower cost and lower environmental impact than iron phosphate. Nevertheless, they are relatively expensive compared to iron minerals and iron metal. The inventors have previously shown that iron mineral concentrates can also be used to manufacture LFP with for main shortcoming, contamination by Si (in the form of SiO2) and other residual impurities that reduce the LFP’s reversible capacity (Talebi et al., J. Solid State Electrochem., DOI 10.1007 / s10008- 015-3049-7 and 10.1007 / sl 0008-016-3324-2). Iron metal proposed use as a partial source of Fe along with complementary Fe2O3(or Fe3O4) has the advantage of higher purity resulting from the iron and steel (low alloy) inherent purification which expels SiO2and other impurities from the mineral gangue in the slag. The use of iron metal, as the sole source of Fe in the melt process of the invention is attractive, since iron is widely available in large volume, well defined chemically with reproducible specifications, and at low cost given its large volume of production. However, for the LFP melt synthesis, iron metal only is not practical, since an additional source of oxygen is required to form LiFePO4. This oxygen could be supplied by oxygen-containing gas mixtures such as O2,C02, and H20, or supplementary reactants such as l_i2CO3and LiH2PO4(which evolve CO2and H2O, respectively).

[0007] A reproducible, well-known, widely available and low-cost source of iron to replace the reactant mixture (iron + iron oxide) is still missing, since metallic iron as the reactant and single source of Fe is not practical presently given the need for a source of oxygen. Alternatively, iron ore concentrates as a source of iron comes with SiO2and other impurities from the gangue leading to batch-to-batch composition variation and more importantly to mine-to-mine composition variation. This also applies to the Fe+2 / Fe+3ratio that requires an additional reducing source. Although these Fe reactants can be used with a proper reducing agent, as shown for example in WO 02 / 27823 and WO 02 / 27824, the cost, quality, reproducibility, and ease of use of such reactants are not yet optimal for wide market share development as required for electric vehicle and large-scale energy storage.

[0008] There is a need for reactant iron sources for use as single iron source in the preparation of cathode materials. In particular, there is a need for such iron sources that are efficient, of controlled purity, cost-effective, and obtained under environmentally friendly conditions.SUMMARY OF THE INVENTION

[0009] The inventors have designed, prepared, and use a reactant iron source of general formula FeOi+xin which x varies between 0.046 and 0.195 (‘FeO’). The reactant iron source according to the invention has a defined and reproducible chemical composition and a rapid kinetic, and is obtained from a first iron source under controlled temperature (T) and oxygen partial pressure (pO2). The first iron source may be iron metal such as for example soft iron, steel, cast iron, and ex-carbonyl iron (carbonyl iron powder). Also, the first iron source may be a purified iron oxide or an iron ore.

[0010] Also, the inventors have designed and conducted a process for preparing a cathode material of general formula LiFei.yMyPO4in which M is iron or a metal of substitution to iron and y varies between 0 and 0.9, or a lithium iron phosphate (LFP) composition, or a lithium manganese iron phosphate (LMFP) composition, the process comprising using the reactant iron source (‘FeO’) according to the invention with a source of lithium and a source of phosphate.

[0011] In embodiments of the invention, the reactant iron source (‘FeO’) can be used as single iron source in the process according to the invention, which can be a melt process, a semi-melt process, or a solid-state process.

[0012] In embodiments of the invention, the reactant iron source is used in a melt process for preparing a cathode material, and a reaction time is less than about 30 minutes, or less than about 10 minutes, or about 2 minutes is achieved.

[0013] In embodiments of the invention, the cathode material, the LFP composition, or the LMFP composition is obtained as ingot or crushed ingot; optionally the ingot or crushed ingot is further subjected to at least one other process including micronization, submicronization, pyrolysis in the presence of a carbon material. These processes may be conducted onsite or at a different location.

[0014] The invention thus provides the following in accordance with aspects thereof:(1). A process for preparing a reactant iron source of general formula FeOi+xin which x varies between 0.046 and 0.195 (‘FeO’), comprising treatment of a first iron source under controlled temperature (T) and oxygen partial pressure (pO2) yielding the reactant iron source, wherein the reactant iron source has a defined and reproducible chemical composition and a rapid kinetic.(2). The process of (1) above, wherein the first iron source is iron metal, a purified iron oxide, or an iron ore; preferably the iron metal is soft iron, steel, cast iron, or ex-carbonyl iron (carbonyl iron powder).(3). A process for preparing a reactant iron source of general formula FeOi+xin which x varies between 0.046 and 0.195 (‘FeO’), comprising: subjecting iron metal to an oxidation reaction under controlled temperature (T) and oxygen partial pressure (pO2) to obtain an iron oxide including Fe2Os or FesC ; and subjecting the iron oxide to a reduction reaction under controlled buffered atmosphere to obtain the reactant iron source; wherein the reactant iron source has a defined and reproducible chemical composition and a rapid kinetic.(4). The process of (3) above, wherein the iron metal is soft iron, steel, cast iron, or excarbonyl iron (carbonyl iron powder).(5). The process of any one of (1) to (4) above, wherein the reactant iron source is obtained at a temperature above about 560°C, or between 600°C and 850°C, or between 600°C and 1250°C.(6). The process of any one of (1) to (5) above, wherein the oxygen partial pressure pO2is between 1.4 x 10-25and 7.0 x 10-17atm or between 1.4 x 10-25and 3.2 x 10-9atm.(7). The process of any one of (1) to (6) above, wherein a desired oxygen partial pressure pO2is reached through a selection of buffered gas mixtures including CO / CO2, H2 / H2O, H2 / O2, CH4 / O2, CH4 / CO2, H2 / CO2, organic compounds suitable for forming buffered compositions by pyrolysis, gasification, or combustion; preferably the buffered gas is pure and / or diluted with an inert gas including argon or nitrogen.(8). The process of (2) above, wherein the first iron source comprises a particulate material with a particle size between 25 pm to 1 mm in at least one dimension.(9). A reactant iron source (‘FeO’) obtained by the process as defined in any one of (1) to (8) above.(10). A reactant iron source of general formula FeOi+xin which x varies between 0.046 and 0.195 (‘FeO’), which has a defined and reproducible chemical composition and a rapid kinetic, wherein the reactant iron source is obtained from a first iron source under controlled temperature (T) and oxygen partial pressure (pO2).(11). A reactant iron source of general formula FeOi+xin which x varies between 0.046 and 0.195 (‘FeO’), which has a defined and reproducible chemical composition and a rapid kinetic, wherein the reactant iron source is obtained from iron metal in a two-step process comprising subjecting the iron metal to oxidation to obtain an iron oxide including Fe2O3or Fe3O4, then reducing the iron oxide under controlled buffered atmosphere yielding the reactant iron source.(12). The reactant iron source of (10) above, wherein the first iron source is iron metal, a purified iron oxide, or an iron ore; preferably the iron metal is soft iron, steel, cast iron, or ex-carbonyl iron (carbonyl iron powder).(13). The reactant iron source of (1 1) above, wherein the iron metal is soft iron, steel, cast iron, or ex-carbonyl iron (carbonyl iron powder).(14). A process for preparing a cathode material which has a general formula LiFei.yMyPO4in which M is a metal of substitution to iron and y varies between 0 and 0.9, or which has a lithium iron phosphate (LFP) or lithium manganese iron phosphate (LMFP) composition, comprising reacting the reactant iron source as defined in any one of (1) to (13) above with a source of lithium and a source of phosphate and optionally a source of manganese or a substitution metal M.(15). The process of (14) above, wherein the reactant iron source is used as a single iron source.(16). The process of (14) or (15) above, which is a melt process, a semi-melt process, or a solid-state process.(17). The process of (14) or (15) above, which is a melt process.(18). The process of (17) above, wherein a reaction time is less than about 30 minutes, or less than about 10 minutes, or about 2 minutes.(19). The process of (17) above, wherein a reaction temperature is between 660°C and 1300°C or between 900°C and 1200°C, and wherein the reaction is conducted under an oxygen buffered atmosphere; optionally the reaction is followed by a cooling step and a solidification step to obtain the reactant iron source as ingots or atomised droplets.(20). The process of any one of (14) to (19) above, wherein the source lithium is Li2CO3, LiOH, Li2SO4, LiH2PO4, LiPO3, l_i3PO4, or a mixture thereof such as l_iPO3-l_i3PO4mixture; and the source of phosphate is P2O5, H3PO4, HPO3, monohydrogen ammonium phosphate (MAP) or dihydrogen ammonium phosphate (DAP), or associated chemicals including LiH2PO4, l_iPO3, l_i3PO4, and mixtures thereof such as l_iPO3-l_i3PO4mixture.(21). The process of any one of (14) to (20) above, wherein the cathode material is obtained as ingot or crushed ingot; optionally the ingot or crushed ingot is further subjected to at least one other process including micronization to obtain a homogeneous granulated powder; optionally the homogenous granulated powder is further subjected tosubmicronization by dry or wet milling or jet milling to obtain a submicronized powder; optionally the submicronized powder is further subjected to pyroly in the presence of at least one source of carbon to obtain an electrochemically active cathode material.(22). The process of any one of (14) to (21) above, wherein the cathode material has the olivine structure.(23). The reactant iron source (‘FeO’) as defined in any one of (9) to (13) above, for use in a process for preparing a cathode material of general formula LiFei.yMyPO4in which M is iron or a metal of substitution to iron and y varies between 0 and 0.9, or in a process for preparing a lithium iron phosphate (LFP) or lithium manganese iron phosphate (LMFP) composition.(24). Use of the reactant iron source (‘FeO’) as defined in any one of (9) to (13) above, in a process for preparing a cathode material of general formula LiFei.yMyPO4 in which M is iron or a metal of substitution to iron and y varies between 0 and 0.9, or in a process for preparing a lithium iron phosphate (LFP) or lithium manganese iron phosphate (LMFP) composition.(25). Cathode material obtained by the process as defined in any one of (14) to (22) above.(26). Battery having a cathode comprising a material obtained by the process as defined in any one of (14) to (22) above.(27). Battery manufacturing plant which embodies the process as defined in any one of (1) to (8) and (14) to (22).

[0015] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0017] In the appended drawings:

[0018] Figure 1 : Phase diagram showing the stability domain of existence of single phase Wustite (‘FeO’) compositions. The region of interest used in Figures 2-5 presented below lies within the dashed box. (Adapted from: Li et al., Metals & Corrosion, DOI: 10.1007 / S10853-019-04027-0).

[0019] Figure 2: Wustite phase stability window for various partial oxygen pressure. Combinations of temperature and partial oxygen pressure can be selected to yield an O / Fe content within the ‘FeO’ phase domain (derived from FACTSage), specific boundary values are shown in Table 2.

[0020] Figure 3: Wustite phase stability window for various CO / CO2buffered gas mixture composition as a function of temperature. The gas mixtures and temperature impart an effective partial oxygen pressure. In absence of dilution, Boudouard effect limits applicability below 700°C (derived from FACTSage).

[0021] Figure 4: Wustite phase stability window for various CO / CO2buffered gas mixture composition with dilution by an inert gas as a function of temperature. With dilution of the gas mixture by an inert gas, Boudouard effect can be mitigated (derived from FACTSage).

[0022] Figure 5: Wustite phase stability window for various H2 / H2O buffered gas mixture composition as a function of temperature. H2 / H2O avoids Boudouard effect (derived from FACTSage).

[0023] Figure 6: TGA signal for FeO conversion from Fe2O3at 750°C under equimolar CO / CO2buffer conditions and reference without conversion under N2atmosphere.

[0024] Figure 7: Typical XRD pattern after thermal treatment under CO / CO2buffer gas mixture at 900°C. FeO phase is mainly found together with some Fe3O4. No starting Fe2O3is visible anymore.

[0025] Figure 8: XRD pattern of the material from Example 7 after 2 minutes reaction time of FeO in the hot pool.

[0026] Figure 9: XRD pattern of the material from Example 8 using carbonyl iron powder (CIP) as an iron source fed into hot pool of l_iPO3.DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0027] Before the present invention is further described, it is to be understood that the invention is not limited to the particular embodiments described below, as variations of these embodiments may be made and still fall within the scope of the appended claims. It is also to be understood that the terminology employed is for the purpose of describing particular embodiments; and is not intended to be limiting. Instead, the scope of the present invention will be established by the appended claims.

[0028] In order to provide a clear and consistent understanding of the terms used in the present specification, a number of definitions are provided below. Moreover, unless defined otherwise, all technical and scientific terms as used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure pertains.

[0029] Use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and / or the specification may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one”. Similarly, the word “another” may mean at least a second or more.

[0030] As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0031] As used herein, the term “ ‘FeO’ ” refers to the reactant iron source according to the invention. It has a general formula FeOi+xin which x varies between 0.046 and 0.195. Also, it has a defined and reproducible chemical composition and a rapid kinetic. The reactant iron source according to the invention is obtained by a process comprising treatment of a first iron source under controlled temperature (T) and oxygen partial pressure (pO2). The first iron source may be iron metal, a purified iron oxide, or an ironore. And the iron source may be soft iron, steel, cast iron, or ex-carbonyl iron (carbonyl iron powder). The reactant according to the invention may be used, among others, in a melt process for preparing a cathode material with a reaction time which is less than about 30 minutes, or less than about 10 minutes, or about 2 minutes.

[0032] As used herein, the term “ex-carbonyl iron” or “carbonyl iron powder (CIP)” refers to iron metal obtained from ex-carbonyl deposition process (i.e., thermal decomposition of metal carbonyl compounds). Such particulate iron presents a high degree of purity. The the reactant iron source according to the invention may be obtained using ex-carbonyl iron. In embodiments of the invention, ex-carbonyl iron is oxidized to an iron oxide such as ‘FeO’ or alternatively as Fe2O3and Fe3O4which is further reduced to obtain the reactant iron source ‘FeO’.

[0033] The present invention benefits from making and using a single source of Fe reactant as ‘FeO’ of well-defined composition obtained out of iron metal, in embodiments of the invention, since soft iron, steel, cast iron are currently produced in large volume from several iron minerals (magnetite, hematite, ilmenite, etc.) or even from recycling iron scrap. Furthermore, new processes are being developed to make green iron by displacing fossil fuels and substituting with renewable hydrogen or ammonia that can also be converted as per the invention to also make a green ‘FeO’ reactant. Although iron oxides (e.g., Fe2O3, Fe3O4) have been demonstrated in the melt process using C, CO / CO2or H2 / H2O reducing agents to fix Fe+2oxidation state, or alternatively using Fe° as a combined reducing agent and complementary iron source, e.g., as a (Fe° + Fe2O3) mixture acting as a chemical equivalent of FeO source according to Eq. 1 outlined above. This solution was found kinetically rapid to form LiFePO4in the melt, but nevertheless does have some drawbacks: pure and well-defined Fe2O3chemical reactant is relatively expensive, and more importantly, the specific gravity of Fe° (7.8 g / cm3) is much higher than that of Fe2O3powder or the LiFePO4melt. We observe a tendency of the Fe° to settle upon addition to the melt with iron rapidly found in the bottom of the crucible, where it may sinter into large, slower reacting lumps. Although this can be alleviated through stirring of the melt, both chemicals could progressively agglomerate or react with the graphite crucible. Depending on the melt temperature and composition, for example, carbon from the graphite container can compete with Fe° as a reducing agent for Fe2O3and needs to be considered in adjusting Fe° and Fe3+sources, unreacted Fe2O3can then contribute to reduce a graphite crucible useful life.

[0034] For these reasons, a single source of iron in the form of a ‘FeO’ of well-defined composition having a specific gravity lower than that of Fe°, as per the present invention is particularly attractive for the melt process. Non-stoichiometric Wustite ‘FeO’ is known to exist at high temperature but is not considered stable as such at ambient temperature. Furthermore, its variable composition is not considered favorable as a reliable chemical reactant.

[0035] Nevertheless, the present invention defines the experimental conditions necessary to form well-defined ‘FeO’ as a single iron reactant source useful for the melt process of the invention. The instability of Wustite at ambient temperature does not affect the overall Fe / O ratio required to form stoichiometric LiFePO4at a well-defined temperature. The use of a buffered gas atmosphere during the synthesis corrects the ‘FeO’ Wustite slight offset from pure Fe2+composition according to Eq. 2 outlined below, where l_iPO3can alternatively be formed in-situ from Li- and P-bearing reactants.(T and p0)'FeO'+LiPO3- - LiFePO4Eq. 2

[0036] The simplicity of a reaction that does not necessitate an additional redox reactant except for the slight correction to a one-to-one Fe / O ratio from buffered atmosphere allows a rapid dwell time to form LiFePO4in less than 30 minutes and even in less that 10 minutes and even in less 2 minutes for improved productivity and graphite crucible useful life.

[0037] In embodiments of the invention, a ‘FeO’ single reactant is made from widely available, low-cost, high purity iron, preferably in particulate form with reproducible specifications by controlled oxidation as described herein below. As an example, low- carbon or cast-iron powders with particle size generally comprised within 50 to 700 pm can be used to form ‘FeO’ as a reactant for LiFePO4. Atomized iron such as Atomet from Quebec Metal Powder QMP (now Rio Tinto) are particularly convenient to make a single ‘FeO’ reactant of defined and reproducible composition to be used directly as sole source of Fe (near Fe+2) especially adapted for the melt process thus benefiting for the known iron purification processes leading to low-C, or cast-iron powders, particularly for low SiO2concentrations and other associated elements. Composition of two typical grades Atomet 1001 HP (reduced iron) and Atomet 56 (cast iron) are summarized in Table 1 below.Table 1. Atomet and concentrated / purified iron oxide references with major impurities present.IOPAtomet 1001 HP Atomet 56 .. ...(lot: 364905) (lot: 116952) concentrate) JFe 99.5% (bal) 93.67% (bal) 69.13%O 600 ppm (COA) 3.19% (COA) 29.99% (bal)C < 40 ppm (COA) 3.27% (COA) NDS 34 ppm (COA) < 100 ppm (spec) ND< 200 m (limit) < 200 m (limit)< 60 ppm (spec) < 100 ppm (spec)Mn 520 ppm (440 ppm 110 ppm 617 ppmCOA)Si < 150 ppm (spec) < 100 ppm (spec) 0.20% 41 ppm 433 ppm 37 ppmCu 175 ppm 244 ppm 1 .6 ppm (ICP-OES)Ti 8.6 ppm 224 ppm 119 ppmCr 305 ppm 793 ppm 272 ppmCa 180 ppm 750 ppm 0.29%Mg 29 ppm 230 ppm 0.16%Al 397 ppm 625 ppm 948 ppmAll values for Atomet 1011 HP and Atomet 56 are from ICP-OES (strong acid digestion); IOP is from fusion-XRF converted from oxide to metal basis, ‘limit’ indicates detection limit; ‘COA’ is from certificate of analysis; ‘spec’ is from specification; ‘bal’ indicates a value obtained from mass balance.

[0038] To achieve the transformation of iron powders into Wustite ‘FeO’ of reproducible known composition, the metal powders are subjected to controlled oxidation, preferably using buffer gas mixtures such as CO / CO2, H2 / H2O, CH4 / O2, and CH4 / CO2(bio-gas), preferably H2 / H2O at temperatures between about 563°C and 1363°C, and composition as determined from thermodynamic calculations at equilibrium as shown herein in the examples below. The preferred Wustite compositions of the invention are FeO(i+x; in which x varies from 0.046 to 0.195 as defined by the temperature and pO2atmosphere used to convert Fe° into well-defined and known Wustite compositions referred to as ‘FeO’. Among those compositions iron-rich are more attractive since closer to 1 to 1 stoichiometry. Table 2 below outlines the compositions made possible at the different temperatures and pO2in equilibrium condition to obtain desired ‘FeO’ reactant to be used forthe melt synthesis. Fluidized, stirred (e.g., rotary kiln), fixed bed, entrained solid reactor known to an expert in the field can be used to obtain rapid conversion equilibrium.Table 2. Experimental parameters of temperatures and oxygen partial pressure limits to respect to obtain a single ‘FeO’ phase of a known and reproducible stoichiometry.... - x-x r- -i Wustite / Wustite-Spinel Wustite / Wustite-Fe boundary . .Temp (°C)7boundaryP(O2) (atm) O / Fe (mol / mol) P(O2) (atm) O / Fe (mol / mol)850 1.378 x 10-181.046 7.083 x W171.120800 9.890 x 10201.047 2.965 x W181.113750 5.509 x 10211.049 9.200 x 1O201.106725 1.170 x 10-211.050 1.430 x 1O201.103700 2.299 x 10-221.051 2.014 x W211.099675 4.159 x 10-231.053 2.579 x W221.094650 6.849 x 10241.056 2.929 x W231.090600 1.370 x 10251.061 2.627 x W251.078

[0039] Upon cooling depending on the kinetic rate, Wustite, which is not thermodynamically stable below 563°C, may disproportionate to a mixture of iron forms summarized as:(T and p0)4 FeO(1+x)- - (1+x)Fe3O4+(1-3x)Fe° Eq. 3

[0040] However, surprisingly with the present invention, these transformations do not interfere with the value of the ‘FeO’ iron reactant of the invention, since whatever the transformation extent, the global chemical composition obtained at room temperature is unchanged and the amount of iron and oxygen within each solid particle, as defined at the high temperature and pO2, is unchanged and is equivalent to ‘FeO’ Wustite composition in the condition of the LFP melt synthesis as illustrated by Eq. 1.

[0041] Another mode of realization of the present invention is to obtain ‘FeO’ reactant from a mine source, such as magnetite or hematite that have been previously concentrated and purified especially, but not limited to the removal of SiO2, the main impurity in most iron concentrates. This is important since although iron metal is widely available and low-cost to form ‘FeO’, an alternative iron-mine source might further reduce the transformation steps required to pass through iron metal and can offer a large reservoir of iron available to make ‘FeO’ as per the present invention, an important advantage considering large markets presently anticipated for LFP and LFMP cathode powders, presently over 1 M tons / year and growing.

[0042] In embodiments of the invention, fine particulate forms of the Fe°such as atomised forms are used. In other embodiments of the invention, particulate iron may be obtainedfrom ex-carbonyl deposition process (i.e., thermal decomposition of metal carbonyl compounds). Such particulate iron presents a high degree of purity and are contemplated in the present invention despite its higher production price. In further embodiments of the invention, other particulate iron of various forms and shapes are contemplated. For example, flakes or needles having at least one dimension smaller than 1 mm could be used for the production of a well-defined ‘FeO’ as they could afterwards be further reduced in size prior to use in the LFP synthesis.

[0043] The parameters of T and pO2given in Table 2 to determine the desired ‘FeO’ composition at equilibrium apply to FeOxas well as to Fe° as starting material. In embodiments of the invention, the two preferred modes to form ‘FeO’ and their use for LiFePO4melt synthesis are represented by the following Eq. 4:(T and p0) (T and p0)Fe° - 'FeO' + l_iPO3- LiFePO4Eq. 4 FeOx

[0044] In embodiments of the invention, the first part of Eq. 4 may be conducted in two steps by first oxidizing totally the metallic iron to FeOx(Fe2O3and / or Fe3O4) then reducing the FeOxto ‘FeO’ under controlled buffered atmosphere.

[0045] As illustrated in the examples herein below describing embodiments of the invention, particulate iron powders or purified low SiO2iron minerals are particularly well adapted to make ‘FeO’ with a rapid equilibrium kinetic from buffered gases compositions leading to a particulate single-Fe reactant that is easy to disperse and react in the melt state. It is a significant improvement as opposed to previously described equivalent (Fe° + FeOx) mixture that tends to separate in the melt because of the high-density iron metal particles (~7.87 g / cc) that is accumulating and sintering into lumps at the bottom of the crucible. Such segregated iron is slower to mix and react and tends to form locally Fe-C chemicals with the crucible material, while unreacted Fe2O3might progressively consume the graphite crucible. Not only the Wustite density is lower (~5.7 g / cc) and closer to the average melt density ~2.75 g / cc, but Wustite is also known to be both Fe+2ion and electron conductor allowing rapid oxide growth, diffusion, and reaction in both liquid and solid states. Although these characteristics of the reactant ‘FeO’ according to the invention are put to use in the melt process, they can also be put to use in other variant synthesis processes involving for example ‘solid-state’ or ‘semi-melt’ reactions. This is also represented by Eq. 2 and 4, since l_iPO3melts at around 650°C while unreacted Wustiteis still solid above 1300°C. In embodiments of the invention, other sources of P and Li can be used instead of LiPO3in addition to the ‘FeO’ of the present invention.

[0046] Although in the present description the use of ‘FeO’ reactant is illustrated in the case of LiFePO4synthesis mainly, the invention also encompasses its use as a reactant to form other iron-containing olivine structures including LFMP in which M is for example Mn or other LFP and LFMP substituted or doped by other element made possible by the present melt process.

[0047] In embodiments of the invention, the source lithium is Li2CO3, LiOH, Li2SO4, LiH2PO4, LiPO3, Li3PO4, or a mixture thereof such as LiPO3-Li3PO4mixture; and the source of phosphate is P2Os, H3PO4, HPO3, monohydrogen ammonium phosphate (MAP) or dihydrogen ammonium phosphate (DAP), or associated chemicals including LiH2PO4, LiPO3, Li3PO4, and mixtures thereof such as LiPO3-Li3PO4mixture.Preparation of the reactant iron source ‘FeO’ according to the invention and its uses in the synthesis of iron-containing olivine structures including well-known LFP and LFMP compositions

[0048] Table 2 above allows for the selection of the oxygen partial pressures, at different temperatures, that respect the pO2limits to form single phase ‘FeO’ Wustites of well- defined and reproducible stoichiometries while avoiding a second Fe° or Fe3O4spinel phase. The phase diagram of Figure 1 illustrates the domain of stability of the single phase ‘FeO’ Wustite. Particulate iron metal powders or purified iron oxides, preferably from iron mines, are used as starting materials, since they are more favorable to rapid reaction and equilibrium with buffered gases. Fluidized, stirred, or high surface thin fixed beds are advantageously used to rapidly form desired ‘FeO’.

[0049] Particulate iron metal, such as obtained by atomisation from melt, e.g., Atomet 1001 HP from Quebec Iron Powder (now Rio Tinto) or cast iron, e.g., Atomet 56, and low- silica purified iron oxide, e.g., Iron Ore Canada (now Rio Tinto), are used to illustrate ‘FeO’ synthesis from metal and oxides leading to a well-defined ‘FeO’. Both metal and oxide powders are widely available with reproducible compositions from steel-making industries as required for large production volume of LFP, LFMP (> million tons / year) used for electrical transport and energy storage in 2022. Table 1 above lists two Atomet powders type and purity along with the concentrated / purified iron mineral used to illustrate the invention.

[0050] In embodiments of the present invention, the well-defined and reproducible ‘FeO’ reactant is obtained either from Fe° or Fe+3-containing iron precursors by reaching thermodynamic equilibrium at a given temperature, preferably comprised between about 563°C and 1363°C, more preferably between about 650°C and 1 100°C. As shown in Figure 2, different Wustite stoichiometries can be fixed depending on the temperature and oxygen partial pressures pO2, since Wustite FeO(i+x; is not a stoichiometric composition. For example, at 750°C, x varies from 0.05 to 0. 1 1 . The data represented in these figures have been generated by FACTSage program (FactSage 8.2, https: / / www.factsage.com, using an in-house database optimized for LFP) and validated experimentally in the examples herein below. Table 2 above lists the pO2values that should be fixed to get the desired ‘FeO’, but such low oxygen partial pressure must, in practice, be fixed by buffered gas compositions currently used in the steel industry as usually represented in the well- known Ellingham diagrams. In practice, control of the oxygen partial pressure at a given temperature that is essential to obtain a Wustite of the desired composition as per the present invention is obtained using buffered gas composition (ratio) such as CO / CO2, H2 / H2O, or through a buffer yielding reacting gas mixture such as H2 / O2, CH4 / O2, CH4 / CO2, preferably H2 / CO2. In the case of buffer yielding reacting gas mixtures, kinetic may benefit from the use of catalysts (such as oxidation or water gas shift catalysts) to rapidly achieve the target buffer gas composition. Dilution of the mixture with an inert gas such as Ar or N2may also be desired to displace / mitigate the Boudouard (C forming) and / or Sabatier (CH4forming) reactions which otherwise limit the effectiveness of gas mixture in the lower range of the temperature window.

[0051] Figures 3, 4, and 5 are implementations of the Figure 2 / Table 2 data using buffer gas mixture ratios to instill oxygen partial pressure levels at given temperatures, thus leading to specific ‘FeO’ compositions. Similar gas ratio calculations may be developed for other gas and reacting gas mixtures. Although the invention can potentially be used to achieve a wide range of well-defined ‘FeO’, in the context of the synthesis of LFP (a Fe2+), the ratio of O / Fe should be selected to be close to the Wustite-Fe boundary, while still within the Wustite region, in order to decrease the extent of reduction required during the LFP synthesis (Eq. 4.).

[0052] The advantages of using a single ‘FeO’ iron source as described in the invention is to benefit from iron reactant purity, availability, and ease of dispersion in the melt as well as shorter reaction time to form LFP since both the reactant and the final product have the same Fe+2oxidation state. Reaction time as short as 2 minutes are shown as possible inthe following example to form LFMP composition using the ‘FeO’ reactant of the invention. Furthermore, the formation of LiFePO4as per Eq. 2 and 4 has the additional benefit to avoid gas formation that might result into foaming thus allowing rapid reaction and equilibrium at a higher introduction rate of the reactants. Only minute amounts of buffered gas mixtures are used during such synthesis to fine tune LFP stoichiometry or correct any accidental Fe+2oxidation or reduction as taught in WO 2015 / 179972 A1.

[0053] In embodiments of the invention, particulate form of the iron precursors used to make ‘FeO’ such as low-carbon or cast-iron powders or purified FeOxmineral is preferred to optimize conversion and equilibrium rate and also because of the ease of dispersion of the ‘FeO’ reactant in the melt pool as used in WO 2013 / 177671 A1. All such iron sources being widely available with reproducible composition from the metal powder metallurgy and can be produced without chemical wasted associated with the production of present iron source, e.g., FePO4and its Na2SO4rejects and wastewater. It is an important advantage of the invention, especially for large production volume, to limit the number of chemical steps and the accumulation of chemical wastes.

[0054] When using an iron ore to form a high purity ‘FeO’ reactant, it is important to limit the concentration of contaminants such as Si, Mg, Ca, and Al. These residues from the gangue can be reduced by mineral concentration and purification through optimized steel making process as exemplified in Table 1 above. As an example, in Talebi et al., J. Solid State Electrochem., DOI 10.1007 / sl 0008-015-3049-7 and 10.1007 / sl 0008-016-3324-2), a net ~0.15% wt. Si (or 0.32% SiO2) in the total Fe sources was found to be acceptable with no / low impact on the LFP cathode reversible capacity. With a net ~1.5% wt. Si (or 3.3% wt. as SiO2) in the total Fe sources resulted in a 3-10 mAh / g reduction of the cathode reversible capacity. In the latter case, the improvements were the result of displacing the contaminant to the grain boundary by adjusting the LFP stoichiometric excesses (Li and P).

[0055] Not only the process of the invention can be carbon free, using H2 / H2O and green electricity, with no or few waste and few conversion steps (using iron or iron ore directly), it could also use iron ore or iron metal processed without the use of carbon or fossil fuels as reducing agent such as from hydrogen or ammonia whenever available to make a green iron precursor for LFP.

[0056] The ‘FeO’ reactant according to the invention not only can secure a wide supply of iron from green source, it can also simplifies the process operation since, as illustratedabove in reaction (Eq. 2) only two reactants of known composition are needed to fix the melt stoichiometry as well as the solid olivine overall composition that will be obtained upon cooling. Another advantage of a particulate ‘FeO’ reactant according to the invention is its ease of dispersion in the melt. Furthermore, there is no need for a redox reaction to happen, since iron is already near the oxidation state +2, like the LFP final product. In these conditions, the use of buffered gas mixtures over the melt to control local pO2during LFP synthesis is only needed to fine tune LiFePO4melt composition and stoichiometry and avoid any accidental Fe+2oxidation or reduction. This is particularly favorable to a rapid LiFePO4formation and equilibrium.

[0057] The melt synthesis used to illustrate the interest of the ‘FeO’ precursor of the invention is merely a preferred mode of realization. It is not limiting, since other synthesis pathways, such as solid-state or semi-melt, can benefit from ‘FeO”s advantageous characteristics. This also applies also to other sources of Li and P that can be used to replace or in-situ form LiPO3, e.g., Li2CO3, P2O5, Li3PO4among others.

[0058] The iron precursor of the invention and its use for olivine phosphate melt synthesis are exemplified mainly with LFP and LFMP well-known compositions, but a skilled person would readily understand that analog compositions also based on the olivine structure could be prepared using the versatility of the melt process. Such analogs being represented globally as LiaFei.xMxPb-yXyOzin which: 0.9 < a < 1.1 , 0.9 < b < 1.1 , 0 < x < 0.9, y < 0.25, 3 < z < 5, M is at least another fixed or aliovalent metal cation of partial substitution to Fe and X is at least another fixed or aliovalent oxyanion of partial substitution to P in the olivine structure, overall substitutions respecting the electroneutrality principle.

[0059] Examples of different compositions and simplified conditions for the synthesis are described in order to illustrate different, non-limiting, mode of realisation of the invention although variants are possible that still encompass the key elements of the present invention.Examples

[0060] The following examples are generally presented to illustrate how to anticipate by calculating and selecting the conditions of ‘FeO’ synthesis from both Fe° and FeOxreactants with a few modes of using those to synthesize LFP and LFMP ingot and optionally convert those into C-LFP or C-LFMP powder. Fluidized bed is selected formaking ‘FeO’ but as will be understood by a skilled person, is in no way the sole technique that could be used in the industry to achieve the same goal.

[0061] Except for the use of a new single phase ‘FeO’ reactant to simplify and optimize the LFP-LFMP synthesis, the other Li-P reactants for the synthesis, that could be used as well as the conditions of the synthesis of the examples, are similar to those described in patent applications of the same family referred to herein above, namely, WO 2005 / 062404 A1 , WO 2013 / 177671 A1 , and WO 2015 / 179972 A1 .

[0062] Although the particulate Fe° or FeOxare favoured, other shapes of starting materials are contemplated, in particular, needles and flakes having at least one dimension smaller than 1 mm. In these cases, the ‘FeO’ formed could be ground to facilitate its reaction and mixing within the melt synthesis of LFP or LFMP.

[0063] Furthermore, in the interest of minimizing the extent of reduction required when using the ‘FeO’ which is slightly O-rich compared to a true FeO, the implementation of the invention would benefit from selecting a ‘FeO’ composition which is near the Wustite / Wustite-Fe boundary, while remaining within the Wustite region of the diagram, thus achieving an ‘FeO’ composition close to a Fe2+.Example 1

[0064] To reduce risk of particle agglomeration, a fluidized bed was used to synthesize the ‘FeO’. The fluidized bed consists of a 15 mm ID by 20 cm long dense bed region expanding to a 30 mm ID by 15 cm long expansion section to limit particle entrainment. The 15 mm tube section has a fritted disk affixed to the tube serving as gas distributor. The fluidized bed is installed in electrically heated, vertical tube furnace capable of reaching temperature up to 1200°C. Insulating material is installed to the tube sections that extend beyond the furnace. The tube is installed so that the fritted disk distributor aligns with the bottom of the furnace heating zone. Fe source in an amount necessary to achieve a 20-30 mm initial bed height at rest is added to the cold system. Inert gas (Ar or N2) is flown through the fluidized bed at a rate sufficient to achieve a superficial gas velocity of 0.3 m / s in the 15 mm section when at the target processing temperature. The inert purged fluidized bed is heated. When the holding temperature is reached the inert gas is replaced with a mixture of CO / CO2adjusted to the same superficial velocity. The system is allowed to operate for 4 hours at this temperature and gas mixture composition. After reaching the hold time, the gas mixture is replaced with inert gas (Ar or N2) to preventfurther reaction during cool down. The three raw chemicals used to form ‘FeO’ are summarized in Table 1 above.Example 1a: Synthesis of ‘FeO’ from low carbon Atomet 1001 HP

[0065] Using the teachings of Table 2 above and Figure 3, a temperature of 775°C and pO2 (using CO / CO2 at a ratio of 1 .5 mol / mol) have been fixed to obtain a ‘FeO’ with a 1.06 O / Fe stoichiometry. XRD and more important Fe analysis confirm the Wustite phase and the predicted stoichiometry.Example 1 b: Synthesis of ‘FeO’ from cast iron Atomet 56

[0066] Same parameters as in Example 1a are used with similar results. This example confirms the equilibrium obtained in these conditions with the oxidation of the residual carbon contained initially.Example 1c: Synthesis of ‘FeO’ from IOP low silica concentrate (Iron Ore Canada)

[0067] Starting with an oxide, the same parameters as in Example 1a and Example 1 b are used with similar results. This example confirms the conditions of equilibrium reached during the treatment, since whatever the initial iron oxidation state, the predicted ‘FeO’ Wustite composition is obtained.Example 2: Synthesis of LiFePO4out of ‘FeO’ of Example 1a

[0068] Using ‘FeO’ of Example 1a and LiPO3, LiFePO4synthesis has been achieved starting with a pool of molten l_iPO3to which the granulated powder ‘FeO’ of Example 1a was added to molten l_iPO3heated up to 1050°C held in a graphite crucible kept under ‘controlled’ pO2(fixed with a CO / CO2) gas mixture. When the melt is cast and solidified, a pure LiFePO4ingot of the olivine structure is confirmed that could be produced and sold as such or converted by milling and coating into ready to use C-LFP cathode powder.Example 3: Synthesis of a typical LFMP composition out of ‘FeO’ of Example 1 a

[0069] The same experimental conditions as in Example 2 are used, except for the addition of MnCO3in calculated quantities to the molten reaction pool in order to form of LiFeo 25Mno 5P04.Example 4: ‘Semi-melt-state’ synthesis of LiFePO4from ‘FeO’ of Example 1a

[0070] Using the ‘FeO’ of Example 1a and LiPO3, LiFePO4synthesis is achieved starting with a solid stoichiometric mixture of finely dispersed powder of ‘FeO’ and l_iPO3placed in a graphite crucible heated and held at 825°C for 5 hours while kept under ‘controlled’ pO2(fixed with a CO / CO2) gas mixture. After cooling, the homogeneous ingot is grinded and analysed by XRD to confirm the LiFePO4structure and purity from such a hybrid synthesis route.Example 5: TGA validation

[0071] The present example is performed in a TGA using a Fe2O3source from commercial source: ARO (Acid Regenerated Oxide) from Remuriate with particle size below 45 pm.

[0072] The powder is heated at 10°C / min to 750°C under N2flow where it is held for 5 minutes. Then the N2flow is replaced by a CO / CO2mixture in equimolar ratio is blown at 25 mL / min for 30 minutes. After this period of time, N2is blown instead of CO / CO2. It is first held for 5 minutes before cooling down to room temperature at 10°C / min. The weight variation of the sample is measured in the TGA.

[0073] Figure 6 shows the TGA measurement as a function of time with comparison to the same powder exposed to the same heating program but fully under N2atmosphere. The weight loss is determined to 8.6% corresponding to the conversion from Fe2O3to FeO Wustite. The conversion in these conditions occurs within 20 minutes.Example 6: Experimental data of FeO conversion

[0074] Similarly to Example 5 but using a fluidized bed with ca. 10 g of Fe2O3precursor, FeO Wustite was produced using the mixture of CO / CO2. The nitrogen flow is held for 90 minutes following the ramp up to ensure uniformity of the powder temperature, while the CO / CO2mixture is blown for 1 hour. Then N2is blown again through the powder during cool down.

[0075] The cold powder is recovered, weighed, and analyzed by XRD. Figure 7 shows the typical pattern of the powder after FeO conversion. No Fe2O3phase is visible. Instead, FeO phase is mainly found along with Fe3O4possibly resulting from the anticipated dismutation of FeO into Fe3O4and Fe mixture upon cooling.

[0076] Table 3 below summarizes the weight ratio according to the thermal and atmosphere conditions. At 900°C, the weight of the final product matches the expectation based on thermodynamic calculations. In contrast, at 700°C, kinetic limitations prevent fast FeO conversion of Fe2O3.Table 3. Experimental conditions for FeO conversion of Fe2O3 precursorsExample 7: Kinetic of reaction for LFMP synthesis using FeO from example as a starting Iron source

[0077] This example uses the measurement of the LiFeMnPO4composition by the lattice parameter to illustrate the exceptional rapid kinetic of the melt reactive pool.

[0078] 34.25 g of LiH2PO4and 27.5 g of MnCO3are placed in a graphite crucible without graphite lid and held 1100°C in order to produce a molten pool of a LiMnPO4+ 25% excess l_iPO3. Once the mixture is totally liquid, 5.75 g of ‘FeO’ produced as in Example 6 at 900°C with a 1 .5 CO / CO2gas mixture is added to the hot pool and held without stirring in the crucible. The iron added is that necessary to produce a LiFe025Mn05PO4overall composition in the liquid melt. 2 minutes after FeO addition, the melt is cast and solidified. After solidification, the ingot is ground below 75 pm particle size and analyzed by XRD in Figure 8. The pattern shows a pure olivine material without trace of Fe impurity (i.e., Fe, FeO, Fe3O4, and Fe2O3). Analysis of the lattice parameters by Rietveld refinement, indicate the formation of pure LiFe025Mn075PO4phase indicating insertion of Fe in the resulting olivine material. This example confirms the feasibility and the fast reaction kinetics with use of the FeO Wustite precursor.

[0079] This is to be compared with state-of-the-art solid-state processes that are associated with several hours dwell times taking into account slower diffusion kinetic in solid phases.Example 8: Use of FeO Wustite from Fe (ex-carbonyl) to produce high purity LFP

[0080] This procedure in this example is similar to the hot feed from the Example 7, however the starting materials is a high purity carbonyl iron powder (CIP), from a commercial source: AmericanCarbonyl with particle size below 10 pm and the aim is to produce LFP. Here prior to the controlled oxidation under CO / CO2at 900°C, the CIP is first oxidized to approach a Fe2O3composition. This oxidation step mitigates the risk of agglomeration of the CIP in the fluidized bed contraption. The oxidation is performed by feeding 10 g of CIP over 30 minutes using a vibratory feeder and passing through an up- flowing air stream through a vertical tube furnace held at 1000°C. 12.9 g of oxidized powder are thus collected.

[0081] The oxidized powder is converted to ‘FeO’ at 900°C with 1 .5 CO / CO2as in Example 6. Note that the direct controlled oxidation of the CIP would be possible in a limited agglomerating configuration, such as with a rotary kiln or a circulating fluidized bed.

[0082] 8.7 g of LiH2PO4is then heated in a graphite crucible to 800°C to create a LiPO3pool. Then 6 g of FeO ex-carbonyl is introduced into the molten LiPO3pool and the crucible is further heated to 1100°C and held at this temperature for 30 minutes. The melt is then cast and solidified into an ingot. The ingot is ground until the particle size is below 75 pm for XRD analysis. The XRD pattern is shown in Figure 9 and shows a 100% pure LFP phase without any Fe impurity.

[0083] As will be understood by a skilled person, other variations and combinations may be made to the various embodiments of the invention as described herein above.

[0084] While the present disclosure has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations including such departures from the present disclosure as come within known or customary practice within the art and as may be applied to the essential features hereinbefore set forth, and as follows in the scope of the appended claims. Features which are described in the context of separate aspects and embodiments of the invention may be used together and / or be interchangeable. Similarly, features described in the context of a single embodiment may also be provided separately or in any suitable sub-combination.

[0085] The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.

[0086] The scope of the claims should not be limited by the preferred embodiments set forth herein above; but should be given the broadest interpretation consistent with the description as a whole.

Claims

CLAIMS:1 . A process for preparing a reactant iron source of general formula FeOi+xin which x varies between 0.046 and 0.195 (‘FeO’), comprising treatment of a first iron source under controlled temperature (T) and oxygen partial pressure (pO2) yielding the reactant iron source, wherein the reactant iron source has a defined and reproducible chemical composition and a rapid kinetic.

2. The process of claim 1 , wherein the first iron source is iron metal, a purified iron oxide, or an iron ore, preferably the iron metal is soft iron, steel, cast iron, or ex-carbonyl iron (carbonyl iron powder).

3. A process for preparing a reactant iron source of general formula FeOi+xin which x varies between 0.046 and 0.195 (‘FeO’), comprising: subjecting iron metal to an oxidation reaction under controlled temperature (T) and oxygen partial pressure (pO2) to obtain an iron oxide including Fe2O3or Fe3O4; and subjecting the iron oxide to a reduction reaction under controlled buffered atmosphere to obtain the reactant iron source, wherein the reactant iron source has a defined and reproducible chemical composition and a rapid kinetic.

4. The process of claim 3, wherein the iron metal is soft iron, steel, cast iron, or ex-carbonyl iron (carbonyl iron powder).

5. The process of any one of claims 1 to 4, wherein the reactant iron source is obtained at a temperature above about 560°C, or between 600°C and 850°C, or between 600°C and 1250°C.

6. The process of any one of claims 1 to 5, wherein the oxygen partial pressure pO2is between 1 .4 x 10-25and 7.0 x 10-17atm or between 1 .4 x 10-25and 3.2 x 10-9atm.

7. The process of any one of claims 1 to 6, wherein a desired oxygen partial pressure pO2is reached through a selection of buffered gas mixtures including CO / CO2, H2 / H2O, H2 / O2, CH4 / O2, CH4 / CO2, H2 / CO2, organic compounds suitable for forming buffered compositions by pyrolysis, gasification, or combustion,preferably the buffered gas is pure and / or diluted with an inert gas including argon or nitrogen.

8. The process of claim 2, wherein the first iron source comprises a particulate material with a particle size between 25 pm to 1 mm in at least one dimension.

9. A reactant iron source (‘FeO’) obtained by the process as defined in any one of claims 1 to 8.

10. A reactant iron source of general formula FeOi+xin which x varies between 0.046 and 0.195 (‘FeO’), which has a defined and reproducible chemical composition and a rapid kinetic, wherein the reactant iron source is obtained from a first iron source under controlled temperature (T) and oxygen partial pressure (pO2).11 . A reactant iron source of general formula FeOi+xin which x varies between 0.046 and 0.195 (‘FeO’), which has a defined and reproducible chemical composition and a rapid kinetic, wherein the reactant iron source is obtained from iron metal in a two-step process comprising subjecting the iron metal to oxidation to obtain an iron oxide including Fe2O3 or Fe3O4, then reducing the iron oxide under controlled buffered atmosphere yielding the reactant iron source.

12. The reactant iron source of claim 10, wherein the first iron source is iron metal, a purified iron oxide, or an iron ore, preferably the iron metal is soft iron, steel, cast iron, or ex-carbonyl iron (carbonyl iron powder).

13. The reactant iron source of claim 11 , wherein the iron metal is soft iron, steel, cast iron, or ex-carbonyl iron (carbonyl iron powder).

14. A process for preparing a cathode material which has a general formula LiFe-i.yMyPC in which M is a metal of substitution to iron and y varies between 0 and 0.9, or which has a lithium iron phosphate (LFP) or lithium manganese iron phosphate (LMFP) composition, comprising reacting the reactant iron source as defined in any one of claims 1 to 13 with a source of lithium and a source of phosphate and optionally a source of manganese or a substitution metal M.

15. The process of claim 14, wherein the reactant iron source is used as a single iron source.

16. The process of claim 14 or 15, which is a melt process, a semi-melt process, or a solid- state process.

17. The process of claim 14 or 15, which is a melt process.

18. The process of claim 17, wherein a reaction time is less than about 30 minutes, or less than about 10 minutes, or about 2 minutes.

19. The process of claim 17, wherein a reaction temperature is between 660°C and 1300°C or between 900°C and 1200°C, and wherein the reaction is conducted under an oxygen buffered atmosphere, optionally the reaction is followed by a cooling step and a solidification step to obtain the reactant iron source as ingots or atomised droplets.

20. The process of any one of claims 14 to 19, wherein the source lithium is l_i2CO3, LiOH, Li2SO4, LiH2PO4, LiPO3, Li3PO4, or a mixture thereof such as l_iPO3-l_i3PO4mixture; and the source of phosphate is P2O5, H3PO4, HPO3, monohydrogen ammonium phosphate (MAP) or dihydrogen ammonium phosphate (DAP), or associated chemicals including LiH2PO4, l_iPO3, l_i3PO4, and mixtures thereof such as l_iPO3-l_i3PO4mixture.

21. The process of any one of claims 14 to 20, wherein the cathode material is obtained as ingot or crushed ingot, optionally the ingot or crushed ingot is further subjected to at least one other process including micronization to obtain a homogeneous granulated powder, optionally the homogenous granulated powder is further subjected to submicronization by dry or wet milling or jet milling to obtain a submicronized powder, optionally the submicronized powder is further subjected to pyroly in the presence of at least one source of carbon to obtain an electrochemically active cathode material.

22. The process of any one of claims 14 to 21 , wherein the cathode material has the olivine structure.

23. The reactant iron source (‘FeO’) as defined in any one of claims 9 to 13, for use in a process for preparing a cathode material of general formula LiFe-i.yMyPCU in which M is iron or a metal of substitution to iron and y varies between 0 and 0.9, or in a process for preparing a lithium iron phosphate (LFP) or lithium manganese iron phosphate (LMFP) composition.

24. Use of the reactant iron source (‘FeO’) as defined in any one of claims 9 to 13, in a process for preparing a cathode material of general formula LiFei.yMyPO4in which M is iron or a metal of substitution to iron and y varies between 0 and 0.9, or in a process for preparing a lithium iron phosphate (LFP) or lithium manganese iron phosphate (LMFP) composition.

25. Cathode material obtained by the process as defined in any one of claims 14 to 22.

26. Battery having a cathode comprising a material obtained by the process as defined in any one of claims 14 to 22.

27. Battery manufacturing plant which embodies the process as defined in any one of claims 1 to 8 and 14 to 22.

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