Method for producing metal-containing compounds

Abstract

A method for producing a carbon-coated metal-containing compound, the method comprising the steps of: a) forming a mixture comprising: i) pitch; ii) one or more alkali metal precursor compound(s); and iii) one or more metal precursor compound(s) comprising one or more metals selected from transition metals, non-transition metals and metalloids, wherein the metal in each metal precursor compound has an initial average oxidation state; and b) heating the mixture to produce a reaction product comprising the carbon-coated metal-containing compound; wherein during heating step b) the initial average oxidation state of the one or more metals in the metal precursor compound is reduced; and wherein at least a portion of the carbon coating comprises sp2 carbons. An electrode active material made according to the method and use of pitch in a carbothermal reduction reaction of a metal precursor compound to produce a carbon coated metal-containing compound, wherein at least a portion of the carbon coating comprises sp2 carbons. Also, a composition comprising LiFePO4 in particulate form prepared according to the method, wherein the particles are at least partially coated with a carbon coating, and wherein at least a portion of the carbon coating comprises sp2 carbons; a battery comprising an electrode comprising a carbon-coated metal-containing compound produced according to the method, optionally wherein the battery is a rechargeable battery, optionally wherein the battery is an alkali metal ion battery, such as a lithium ion battery. Lastly, use of a carbon-coated metal-containing compound produced according to the method as an electrode in a rechargeable battery, optionally wherein the battery is an alkali metal ion battery, optionally wherein the battery is a lithium ion battery.

Description

[0001]METHOD FOR PRODUCING METAL-CONTAINING COMPOUNDS CROSS REFERENCE TO RELATED APPLICATIONThe present application claims the priority of United Kingdom Patent Application No.2409902.0, filed on 8 July 2024, the entirety of which is herein incorporated by reference.FIELD OF THE INVENTIONThe present invention relates to methods for producing metal-containing compounds whichcan be used as electrode materials for batteries, capacitors, or other energy storagedevices. BACKGROUNDMetal-containing compounds, such as alkali metal phosphates, have attracted considerableattention in recent years due to their high capacity, good rate performance, and improved stability as electrode materials for various energy storage devices.One well-established approach for synthesizing electrode materials is the carbothermalreduction (CTR) process. In this process, a metal precursor compound (e.g. Fe2O3, Fe3O4,and FePO4) is heated at elevated temperature in the presence of an alkali metal precursorcompound and an excess of particulate carbon under an inert or reducing atmosphere toform a compound containing a reduced metal or metal alloy (e.g. Fe2+) and carbonmonoxide or carbon dioxide as by-products. As shown in Figure 1, the excess particulatecarbon forms an electrically conductive matrix (103) between the particles of metal-containing compounds (101) in the product. The reaction temperature, time, andatmosphere can be adjusted to control the size, morphology, composition, and phasepurity of the product.Prior art disclosures of the CTR process can be found, for example, in US6528033,US6702961, US6716372, US6730281, US6794084, US6960331, US7060206,US7276218, and US8163430 which are incorporated herein by reference, andUS10050271B2, which is also incorporated herein by reference and which describesmethods for performing carbothermal reduction of metal precursor compounds in thepresence of elemental phosphorus.However, a problem associated with the use of particulate carbons in the CTR process isthat they do not coat the individual LiFePO4particles but rather provide point contactsbetween adjacent particles and agglomerates. This can lead to poor utilization of the activematerial during battery operation. There is therefore a need for a method of producingcarbon-coated metal-containing compounds which have desirable properties that renderthem useful as electroactive materials in energy storage applications.SUMMARY OF THE INVENTIONIn accordance with a first aspect of this invention, there is provided a method for producing a carbon-coated metal-containing compound, the method comprising the steps of: a) forming a mixture comprising: i) pitch; ii) one or more alkali metal precursor compound(s); and iii) one or more metal precursor compound(s) comprising one or moremetals selected from transition metals, non-transition metals and metalloids, wherein the metal in each metal precursor compound has aninitial average oxidation state; and b) heating the mixture to produce a reaction product comprising the carbon-coated metal-containing compound; wherein during heating step b) the initial average oxidation state of the one or more metalsin the metal precursor compound is reduced.The carbon-coated metal-containing compound comprises a carbon coating, wherein at least a portion of the carbon coating comprises sp2carbons.In the method, the pitch, alkali metal precursor compound, and metal precursor compoundreact to form particles of a carbon-coated alkali metal-metal composite product. The pitchforms a coating on the particles of precursor material. During heating, the precursormaterials react to form a reduced metal-containing compound, without full reduction ofthe metal to an elemental state, and the pitch is decomposed in an inert atmosphere(pyrolyzed) to form a carbon coating on the particles. Some of the pitch also forms anelectrically conductive carbon matrix between the carbon-coated metal particles, resulting in a highly electrically conductive composite material which has advantageous propertieswhen used to form an electrode, such as a cathode, of a battery, capacitor, or other energystorage device. Pitch has a high percentage carbon content and therefore also has a high carbon to oxygen ratio. This produces in a high carbon content coating on pyrolysis. The high C to O ratioalso results in the formation of graphitic sp2 carbon on pyrolysis, particularly in thepresence of Fe-containing precursors that are known to catalyse the graphitization processat relatively low reaction temperatures. Furthermore, pitch (including coal tar pitch,bitumen, asphalt etc.) can help in the precursor compaction process prior to heating andcan assist in the reduction of other transition metals e.g. Mn3+. The pitch may be selected from coal tar pitch, asphalt, bitumen, or combinations thereof.The metal-containing compound produced by the method may have the formula:AaMb(XcYd)eZf Formula (I) wherein:A is an alkali metal selected from one or more of lithium, sodium and potassium;M comprises one or more metals selected from transition metals, non-transition metals, and metalloids; (XcYd)eis at least one first anion; and Z is at least one second anion; wherein a ≥0; b >0; c >0; d ≥0; e >0 and f ≥0; wherein a, b, c, d, e and f are chosen to maintain electroneutrality; wherein X comprises one or more elements selected from titanium, vanadium, chromium, arsenic, molybdenum, tungsten, niobium, manganese, aluminium, selenium, boron, oxygen, carbon, silicon, phosphorus, nitrogen, sulfur, fluorine, chlorine, bromine and iodine; and wherein Y is selected from one or more halides, sulfur-containing groups, oxygen- containing groups and mixtures thereof. Compounds of this formula are ideally suitable for use as electrode materials, andparticularly as cathode materials, in alkali metal batteries, such as Li-ion, Na-ion and K-ion batteries.In the above formula, M may be a metal selected from one or more of titanium, vanadium, niobium, tantalum, hafnium, chromium, molybdenum, tungsten, manganese, iron, osmium, cobalt, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, aluminium, scandium, yttrium, zirconium, technetium, rhenium, ruthenium, rhodium, iridium, mercury, gallium, indium, tin, lead, bismuth, magnesium, calcium, beryllium, strontium and barium, boron, silicon, germanium, arsenic, antimony and tellurium.Z may be selected from one or more halides, hydroxide-containing groups and mixturesthereof. X may comprise phosphorus.(XcYd)e may be a PO4 and / or P2O7 moiety.The metal-containing compound produced by the method may be selected from one ormore of the group consisting of LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4, NaFePO4, NaMnPO4, NaCoPO4, NaNiPO4, LiMn0.5Fe0.2Mg0.3PO4, Li3V2(PO4)3, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, LiMn0.5Fe0.5PO4, Na7V4(P2O7)4PO4, Na7V3(P2O7)4, Na2Fe(SO4)2, NaVPO4F, LiVPO4F, Na3V(PO4)2, Li3V(PO4)2, LiVP2O7, NaVOPO4, LiVOPO4, LiV2O5, NaV2O5, NaVO2, VPO4, MoP2O7, MoOPO4, Fe3(PO4)2, Na8−2xFe4+x(P2O7)4, Na8−2xMn4+x(P2O7)4, Na2MnP2O7, Na2FeP2O7, Na2CoP2O7, Na4Mn3(PO4)2P2O7, Na4Co3(PO4)2P2O7, Na4Ni3(PO4)2P2O7, NaFeSO4F,LiFeSO4F, NaMnSO4F, LiMnSO4F, Na2Fe2(SO4)3, Li2Fe2(SO4)3, Li2Fe(SO4)2, Na2FePO4F,Na2MnPO4F, Na2CoPO4F, Na2NiPO4F, Na3V2(PO4)2F3, KVPO4F, KVOPO4, K3V2(PO4)3,K3V2(PO4)2F3, KFePO4, and KCoPO4.The metal-containing compound produced by the method may have the formula: LiMPO4,where M is a metal selected from one or more of manganese, iron, cobalt, nickel, copper, zinc, magnesium, calcium and combinations thereof.The metal-containing compound produced by the method may be selected from LiFePO4,LiFe1-xMnxPO4, LiFe1-xMgxPO4and LiFe1-x-yMnxMgyPO4. In the latter two compounds, Mg maybe present in <10 wt%, preferably <5 wt%.The metal precursor compound may comprise Fe. The metal precursor compound may be selected from one or more of FeCO3, Fe2O3, Fe3O4, FeOOH, FePO4.xH2O, FePO4, Fe3(PO4)2, FeSO4.xH2O, Fe(NO3)3, Fe(CH3CO2)2, C6H8O7xFe3+.yNH3(ammonium iron (III) citrate), C6H5FeO7(iron (III) citrate) and Fe(C5H7O2)3(iron (III) 2,4-pentanedionate), wherein x, y are ≥0.The mixture may comprise one or more compounds or hydrates thereof selected fromLiH2PO4, Li3PO4, LiPO3, Li2CO3, Li2SO4, Lithium citrate, Li2HPO4, LiOH, H3PO4, (NH4)2HPO4and (NH4)H2PO4, preferably LiH2PO4or Li2CO3.The heating step b) may include heating the mixture at a temperature proximate to orabove the melting point of the pitch. This may permit the pitch to melt over and coat themetal particles prior to conversion of the pitch to carbon by pyrolysis.The heating step b) may comprise heating at a first temperature sufficient to melt thepitch and heating at a second temperature sufficient to convert the pitch to carbon,optionally wherein the first temperature is in the range of 50 °C to 250 °C and whereinthe second temperature is in the range of 300 °C to 1500 °C. Improved coating of the metal particles may be achieved by having a two-step heating process, wherein theparticles are coated with molten pitch in the first heating step, and then the pitch coatingis pyrolyzed to form a carbon coating on the particles in the second step. The temperature of the first step may be selected to correspond to the melting point of the pitch, and the temperature of the second step may be selected to correspond to the temperature of pyrolysis.The first temperature may be maintained for a period of 1 to 100 minutes and the secondtemperature may be maintained for a period of 1 to 500 minutes.At least part of the pitch may be converted to elemental carbon during heating at thesecond temperature. Optionally, at least part of the pitch may be converted to sp2hybridized carbon. Conversion of the pitch to sp2 carbon may result in graphitisation of thecarbon, which may enhance electrical connectivity. Fe compounds advantageously catalysethe graphitisation reaction. In order to obtain as high a conductivity as possible with asminimal an amount of carbon as possible, at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95%, or a range between any two of the aforementioned values, of the carbon atoms in the carbon coating may be sp2hybridized carbon. In step a), the mixture may further comprise particulate carbon, and / or one or morecarbon-containing polymers, and / or a hydrocarbon. The particulate carbon and carbon-containing polymer may connect the particles together into an electrically connectednetwork or matrix. In some examples, the mixture may comprise:- pitch (such as coal tar pitch) and polyethylene (such as high moduluspolyethylene), or -pitch (such as coal tar pitch) and polypropylene (such as high moduluspolypropylene), or -pitch (such as bitumen) and polyethylene (such as high modulus polyethylene), or- pitch (such as bitumen) and polypropylene (such as high modulus polypropylene),or -pitch (such as coal tar pitch), particulate carbon, and polyethylene (such as highmodulus polyethylene), or -pitch (such as coal tar pitch), particulate carbon, and polypropylene (such as highmodulus polypropylene), or -pitch (such as bitumen), particulate carbon, and polyethylene (such as highmodulus polyethylene), or -pitch (such as bitumen), particulate carbon, and polypropylene (such as highmodulus polypropylene). The particulate carbon may be present in the mixture in an amount of greater than 0% to 50% by weight, or from 2% to 50%, or 5% to 20%, based on the combined weight of the pitch and particulate carbon. The particulate carbon may enhance the tap density and / or compressibility of the carbon-coated metal-containing compound without (substantial) loss of specific capacity.The particulate carbon and pitch may be present in a mass ratio of from 10:90 to 90:10,from 25:75 to 75:25, from 40:60 to 60:40, or about 50:50 with respect to each other. The carbon-coated metal-containing compound produced by the method may have a total carbon content of from 1 to 5% by weight carbon.The pitch may be petroleum-derived pitch (i.e. asphalt or bitumen), coal-derived pitch(i.e. tar), or plant-derived pitch (i.e. rosin).The pitch may be soluble in a solvent. Optionally, the solvent may be a non-polar organicsolvent, such as an alkane (pentane, hexane, or heptane), an aromatic (pyridine, benzene,toluene, or xylene), methylene chloride, chloroform, methyl acetate, ethyl acetate, methylethyl ketone, diethyl ether, a carbonate (such as propylene carbonate, ethylene carbonate,dimethyl carbonate, diethyl carbonate etc.), an ether (such as diglyme, triglyme,tetrahydrofuran, dioxane etc), or combinations thereof. Optionally, the method maycomprise mixing the pitch in the solvent and evaporating the solvent prior to or duringheating. The solvent may improve mixing of the precursors and the pitch.The quantity of pitch used in the method may be sufficient to provide a stoichiometricmolar excess of carbon with respect to the metal precursor compound.The method may further comprise contacting the mixture with a reducing gas duringheating step b). Optionally, the reducing gas may be selected from CO, H2, andcombinations thereof. The reducing gas may assist in reducing the metal precursorcompound and thereby accelerate the reaction. Advantageously, the reducing gas may begenerated in situ during pyrolysis of the pitch. Alternatively, the reducing gas may beadded to the reaction mixture prior to or during heating.In accordance with a second aspect of this invention, there is provided a use of pitch in acarbothermal reduction reaction of a metal precursor compound to produce a carboncoated metal-containing compound. The carbon-coated metal-containing compoundcomprises a carbon coating, wherein at least a portion of the carbon coating comprises sp2carbons.In accordance with a third aspect of this invention, there is provided a use of pitch andparticulate carbon in a carbothermal reduction reaction of a metal precursor compound toproduce a carbon-coated metal-containing compound. The carbon-coated metal-containing compound comprises a carbon coating, wherein at least a portion of the carbon coating comprises sp2carbons.In accordance with a fourth aspect of this invention, there is provided an electrode activematerial made according to the above method.In accordance with a fifth aspect of this invention, there is provided a compositioncomprising LiFePO4in particulate form prepared according to the above method, wherein the particles are at least partially coated with a graphitic coating.In accordance with a sixth aspect of this invention, there is provided a battery comprisingan electrode comprising a carbon-coated metal-containing compound produced accordingto the above method. Optionally, the battery may be a rechargeable battery. Optionally,the battery may be an alkali metal ion battery, such as a lithium-ion battery or a sodium-ion battery.In accordance with a seventh aspect of this invention, there is provided a use of a carbon-coated metal-containing compound produced according to the above method as an electrode in a rechargeable battery. Optionally, the battery may be an alkali metal ionbattery, such as a lithium-ion battery or a potassium-ion battery. The advantages of the second, third, fourth, fifth, sixth and seventh aspects may correspond to those of the first aspect. Unless otherwise stated, each of the integers described may be used in combination with any other integer as would be understood by the person skilled in the art. Further, althoughall aspects of the invention preferably “comprise” the features described in relation to thataspect, it is specifically envisaged that they may “consist” or “consist essentially” of thosefeatures outlined in the claims. In addition, all terms, unless specifically defined herein, are intended to be given their commonly understood meaning in the art. As used herein and in the accompanying claims, unless the context requires otherwise,“comprise” or variations such as “comprises” or “comprising” will be understood to implythe inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.The term “consist(s) / (ing) essentially of”, with respect to the components of a compositionor mixture, means the composition or mixture contains the indicated components and may contain minor additional components in an amount less than 1 wt% based on the total weight of the composition or mixture, and provided that the additional components do not substantially alter the reactivity of the composition or mixture. Further, in the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, is to be construed as an implied statement that each intermediate value of said parameter, lying between the smaller and greater of the alternatives, is itself also disclosed as a possible value for the parameter. In addition, unless otherwise stated, all numerical values appearing in this application are to be understood as being modified by the term “about”. As used herein, the term “about”means that the stated value can vary by ± 10%. For example, about 90 wt% means 90±9wt%, and about 0.1 wt% means 0.1±0.01 wt%. When used with reference to a range, the term “about” applies to all values in the range. As used herein, the term “carbon-coated” will be understood to refer to a layer of carbondeposited on the surface of a particle or agglomerate of the metal-containing compound.The carbon coating covers >50%, preferably >80%, more preferably >90%, and mostpreferably >99% of the surface area of the particle or agglomerate. The % coverage canbe determined visually by transmission electron microscopy. “Metal-containing compound” refers to a compound, composite, salt, or complex which contains one or more metals. The metal may be in ionic form or neutral form. “Alkali metal precursor compound” refers to a compound, composite, salt, or complex which contains one or more alkali metals and which is used as a starting material for the reaction of the method. The metal may be in ionic form or neutral form and may beselected from Li, Na, K, Rb, Cs or Fr, preferably, Li, K or Na. The alkali metal precursorcompound contributes an alkali metal atom to the metal-containing compound producedby the method.“Pitch” refers to highly viscous liquids, which may in some cases appear solid, obtainedfrom petroleum, coal or plant sources. Petroleum-derived pitch is also known as asphaltor bitumen, coal-derived pitch is also known as tar (or coal tar pitch), and plant-derivedpitch is also known as resin or rosin. Pitch is a viscoelastic polymer. Pitch sourced frompetroleum or coal contains polyaromatic hydrocarbons (PAHs), which may be selected from naphthalene, acenaphthene, acenaphthylene, fluorene, anthracene, phenanthrene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi)perylene,dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene, and combinations thereof. Therefore,pitch can be characterised as including at least two, but preferably at least 3, 4, 5, 6 7, 8,9, 10, 11, 12, 13, 14, 15, or all, of the above-listed PAHs.“Tar” refers to a black thermoplastic type of pitch produced by the destructive distillationof coal – sometimes referred to as coal tar. Tar is also a residue in the manufacture of coalgas and coke. It may also be derived from plants such as pine trees.“Asphalt” refers to a sticky, black and highly viscous liquid or semi solid that is present incrude oil and in some natural deposits sometimes termed asphaltum. In US terminologyasphalt (or asphalt cement) is the carefully refined residue from the distillation process ofselected crude oils. Outside of the US, the product is called bitumen. Asphalt is a type ofpitch derived from crude petroleum. Asphalt contains, among other hydrocarboncomponents, asphaltenes, which have a C:H ratio of approximately 1:1.2 and a distributionof molecular masses in the range of 400 u to 1500 u.The present invention will be better understood in light of the following examples and theaccompanying figures, which are given in an illustrative manner only and should not beinterpreted in a restrictive manner. BRIEF DESCRIPTION OF THE FIGURES In the accompanying Figures: Figure 1 shows a TEM image of an LiFePO4 particle (101), which is not according tothe present invention, surrounded by a matrix of particulate carbon (103).Figure 2 shows a TEM image of an LiFePO4 particle (201) according to the present invention which comprises a carbon coating (203).Figure 3 shows a Raman spectrum of carbon-coated LiFePO4 particles of the samecomposition as the particle of Figure 2. Figure 4 is an XRD diagram of a sample prepared according to Comparative Example 1.Figure 5 shows the constant current data for the LiFePO4 cathode active materialof Comparative Example 1 (made using LiH2PO4, Fe2O3 and C65 particulate carbon).Figure 5 shows the voltage profile (electrode potential versus specific capacity) forcycle 2. The current density was set to an equivalent rate of C / 10 assuming a reversible specific capacity of 150 mAh / g for the active material (where a 1 C rate is a rate equivalent to a 1-hour charge and a 1-hour discharge).Figure 6 shows the XRD diagram for LiFePO4 cathode active material preparedaccording to Example 1 (using Li2CO3, FePO4 and coal tar pitch).Figure 7 shows the constant current data for the LiFePO4cathode active material of Example 1. Figure 8 shows the XRD diagram for LiFePO4 cathode active material preparedaccording to Example 2 (using Li2CO3, FePO4, coal tar pitch and high modulus polyethylene powder). Figure 9 shows the voltage profile (electrode potential versus specific capacity) forthe LiFePO4 cathode active material prepared according to Example 2. Figure 10 shows the differential capacity data for the LiFePO4cathode activematerial prepared according to Example 2.Figure 11 shows the XRD diagram for LiFePO4 cathode active material preparedaccording to Example 3 (using Li2CO3, FePO4, coal tar pitch and particulate carbon). Figure 12 shows the voltage profile (electrode potential versus specific capacity) for the LiFePO4 cathode active material prepared according to Example 3. Figure 13 shows the XRD diagram for LiFePO4cathode active material preparedaccording to Example 4 (using Li2CO3, FePO4, coal tar pitch and HMPE).Figure 14 shows the voltage profile (electrode potential versus specific capacity)for the LiFePO4 cathode active material prepared according to Example 4.Figure 15 shows the differential capacity data for the LiFePO4cathode activematerial prepared according to Example 4.Figure 16 shows the XRD diagram for LiFePO4cathode active material preparedaccording to Example 5 (using Li2CO3, FePO4, coal tar pitch and HMPE).Figure 17 shows the voltage profile (electrode potential versus specific capacity)for the LiFePO4 cathode active material prepared according to Example 5.Figure 18 shows the XRD diagram for LiFePO4 cathode active material preparedaccording to Example 6 (using LiH2PO4 / FeOOH / CTP).Figure 19 shows the voltage profile (electrode potential versus specific capacity)for the LiFePO4 cathode active material prepared according to Example 6.Figure 20 shows the differential capacity data for the LiFePO4cathode activematerial prepared according to Example 6.Figure 21 shows the XRD diagram for LiFePO4 cathode active material preparedaccording to Example 7 (using LiH2PO4 / FeOOH / CTP+HMPE).Figure 22 shows the voltage profile (electrode potential versus specific capacity)for the LiFePO4 cathode active material prepared according to Example 7. Figure 23 shows the differential capacity data for the LiFePO4cathode active material prepared according to Example 7.Figure 24 shows X-ray diffraction patterns for LiFePO4 (ZL 250M, 0% excess), whereparticulate carbon has been added in proportions of 0%, 2.5%, 5%, 10%, 20%,50%. Figure 25 shows LiFePO4 (ZL 250M, 0% excess) 0.1C 2nd cycle discharge specificcapacity where particulate carbon has been added in proportions of 0%, 2.5%, 5%,10%, 20%, 50%. Figure 26 shows LiFePO4 (ZL 250M, 0% excess) tap density where particulatecarbon has been added in proportions of 0%, 2.5%, 5%, 10%, 20%, 50%.Figure 27 shows LiFePO4 (ZL 250M, 0% excess) compressed density (2500 psi)where particulate carbon has been added in proportions of 0%, 2.5%, 5%, 10%,20%, 50%.DETAILED DESCRIPTION The present invention provides a new, scalable method for producing a carbon-coated metal-containing compound which can be used as an electrode material for various typesof batteries, such as alkali metal-ion batteries (e.g. lithium-ion batteries and sodium-ionbatteries). The method uses carbothermal reduction (CTR) of precursor compounds in thepresence of pitch. It has been discovered that pitch is useful as the reducing agent andthe elemental carbon source for the synthesis of Li-ion and K-ion cathode active materialssuch as LiFePO4 (LFP), LiFe1-xMnxPO4 (LMFP), KFePO4 (KFP), KFe1-xMnxPO4 (KMFP) andothers. During the pyrolysis process the pitch is decomposed in situ to elemental carbon.Advantageously, the pitch may also produce reducing gases (such as CH4, H2 andcombinations thereof) during decomposition. The reducing gases may be useful for reducing the metals in the metal precursor compounds (for example, reducing Fe3+to Fe2+and Mn3+to Mn2+). The method involves forming a mixture of pitch, one or more alkali metal precursor compounds, and one or more metal precursor compounds, and heating the mixture to produce a reaction product comprising the carbon-coated metal-containing compound. During the heating process, the initial average oxidation state of the metal in the metalprecursor compound is reduced. The pitch serves as both a carbon source and a reducingagent for the metal precursor compound and also forms a carbon coating on the surfaceof the metal-containing compound produced by the method, which can improve theconductivity, stability, and performance of the material when used as an electrodematerial. The carbon is believed to act as a reducing agent and is itself oxidized to formCO and CO2in varying proportions. As shown in Figure 2, the carbon coating (203) forms a thin layer over the particles of the metal-containing compound LiFePO4(201).Advantageously, the pitch also assists in compaction / pelletization of the mixture prior toheating by acting as a binder. This enhanced compaction minimises gaps between thereactant particles, aids the kinetics of the solid-state CTR reaction, and generally improvesproduct formation.The pitch used in the method of the invention can be derived from suitable source(including petroleum, coal and plant matter) provided that it can decompose under heatto form carbon and volatile products. Suitable examples include petroleum-derived pitch(i.e. asphalt or bitumen), coal-derived pitch (i.e. tar), plant-derived pitch (i.e. resin or rosin), or any combination thereof. The pitch may be soluble in a solvent. Optionally, the solvent may be a non-polar organic solvent, such as an alkane (pentane, hexane, or heptane), an aromatic (pyridine, benzene, toluene, or xylene), methylene chloride, chloroform, methyl acetate, ethyl acetate, diethyl ether, a carbonate (such as propylene carbonate, ethylene carbonate, dimethyl carbonate,diethyl carbonate etc.), an ether (such as diglyme, triglyme etc), or a combination thereof.The method can include a step of dissolving the pitch in a solvent to facilitate the dispersionand mixing of the pitch with the metal precursor particles. The solvent can be evaporatedprior to or during the heating process, leaving behind a uniform heterogeneous mixture ofthe pitch and the metal precursor particles. The evaporation of the solvent can alsogenerate gas that can assist in the reduction of the metal precursor compounds and contribute to the formation of the carbon coating. The use of a solvent can improve the quality and uniformity of the electrode material produced by the method of the invention.In some embodiments, including a step of dissolving the pitch in a solvent can result in acarbon-coated metal-containing compound which when used as an electrode material,produces a higher specific capacitance and lower resistance than electrode materialprepared without the dissolution step.The quantity of pitch used in the method can be sufficient to provide a stoichiometric molarexcess of carbon with respect to the metal precursor compound. This is so that sufficientcarbon is present to act as a reducing agent for the metal precursor compound and providea carbon coating. The molar equivalents of carbon can be calculated based on the weightper gram-mole of carbon atoms.The alkali metal precursor compound used in the method can be any compound thatcontains one or more alkali metals, such as lithium, sodium, potassium, rubidium,caesium, or francium, preferably, lithium, sodium or potassium. Examples of suitable alkalimetal precursor compounds include, but are not limited to, alkali metal salts, alkali metal phosphates, alkali metal oxides, alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, alkali metal sulfates, alkali metal hydroxides, alkali metal nitrates, alkali metal nitrides, alkali metal halides, alkali metal organometallic compounds, or anycombination thereof. In some embodiments, the alkali metal precursor compound can beselected based on the type of the battery to be produced, such as lithium-containing precursor compounds for lithium-ion batteries, sodium-containing precursor compounds for sodium-ion batteries, potassium-containing precursor compounds for potassium-ion batteries, or other alkali metal precursor compounds for other alkali metal-ion batteries.The alkali metal precursor compound can comprise one or more compound(s) orhydrate(s) thereof selected from LiH2PO4, Li3PO4, LiPO3, Li2CO3, Li2SO4, Lithium citrate,Li2HPO4, LiOH, H3PO4, optionally in combination with (NH4)2HPO4 and / or (NH4)H2PO4.Preferably the alkali metal precursor compound is LiH2PO4 or Li2CO3.The metal precursor compound(s) used in the method of the invention can be anycompound that contains one or more metals, such as transition metals, non-transitionmetals, or metalloids, in their chemical structure. The metal in the metal precursorcompound can have an initial average oxidation state, which can be zero or a positiveinteger. Examples of suitable metal precursor compounds include, but are not limited to, metal salts, metal oxides, metal hydroxides, metal sulfates, metal nitrates, metal nitrides, metal halides, metal sulfides, metal phosphates, metal phosphides, metal carbonates, metal bicarbonates, metal carboxylates, metal organometallic compounds, or anycombination thereof. The metal precursor compound can provide the metal element forthe metal-containing compound produced by the method, which can act as an activematerial for the electrode material. In some embodiments, the metal precursor compound(s) can be selected based on the desired properties and performance of the electrode material, such as the capacity, the voltage, the rate capability, the cycle life, the safety, or the compatibility with the electrolyte and the current collector. The metal-containing compound produced by the method can have the formula: AaMb(XcYd)eZfformula (I) wherein: A is an alkali metal selected from one or more of lithium, sodium and potassium; M comprises one or more metals selected from transition metals, non-transition metals, and metalloids; (XcYd)eis at least one first anion; and Z is at least one second anion; wherein a ≥0; b >0; c >0; d ≥0; e >0 and f ≥0; wherein a, b, c, d, e and f are chosen to maintain electroneutrality; wherein X comprises one or more elements selected from titanium, vanadium, chromium, arsenic, molybdenum, tungsten, niobium, manganese, aluminium, selenium, boron, oxygen, carbon, silicon, phosphorus, nitrogen, sulfur, fluorine, chlorine, bromine and iodine; and wherein Y is selected from one or more halides, sulfur-containing groups, oxygen- containing groups and mixtures thereof. Examples of suitable metals for M in the above formula include a metal selected from the group consisting of titanium, vanadium, niobium, tantalum, hafnium, chromium, molybdenum, tungsten, manganese, iron, osmium, cobalt, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, aluminium, scandium, yttrium, zirconium, technetium, rhenium, ruthenium, rhodium, iridium, mercury, gallium, indium, tin, lead, bismuth, magnesium, calcium, beryllium, strontium and barium, boron, silicon, germanium, arsenic,antimony and tellurium or any combination thereof.The metal-containing compound produced by the method can be selected from one ormore of the group consisting of LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4, NaFePO4, NaMnPO4, NaCoPO4, NaNiPO4, LiMn0.5Fe0.2Mg0.3PO4, LiFe0.1Mn0.9PO4, LiFe0.2Mn0.8PO4, LiFe0.3Mn0.7PO4, LiFe0.4Mn0.6PO4, LiFe0.5Mn0.5PO4, LiFe0.95Mg0.05PO4, LiFe0.9Mg0.1PO4, LiFe0.1Mg0.05Mn0.85PO4, LiFe0.2Mg0.05Mn0.75PO4, Li3V2(PO4)3, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, LiMn0.5Fe0.5PO4, Na7V4(P2O7)4PO4, Na7V3(P2O7)4, Na2Fe(SO4)2, NaVPO4F, LiVPO4F, Na3V(PO4)2, Li3V(PO4)2, LiVP2O7, NaVOPO4, LiVOPO4, LiV2O5, NaV2O5, NaVO2, VPO4, MoP2O7, MoOPO4, Fe3(PO4)2, Na8−2xFe4+x(P2O7)4, Na8−2xMn4+x(P2O7)4, Na2MnP2O7, Na2FeP2O7, Na2CoP2O7, Na4Mn3(PO4)2P2O7, Na4Co3(PO4)2P2O7, Na4Ni3(PO4)2P2O7, NaFeSO4F, LiFeSO4F, NaMnSO4F, LiMnSO4F, Na2Fe2(SO4)3, Li2Fe2(SO4)3, Li2Fe(SO4)2, Na2FePO4F, Na2MnPO4F, Na2CoPO4F, Na2NiPO4F, Na3V2(PO4)2F3, KVPO4F, KVOPO4, K3V2(PO4)3, K3V2(PO4)2F3, KFePO4, andKCoPO4. In some embodiments, the metal containing compound can be selected from oneor more of LiFePO4, LiFe1-xMnxPO4, LiFe1-xMgxPO4and LiFe1-x-yMnxMgyPO4, wherein in the latter two compounds, Mg is present in an amount of less than 10%, or less than 5%.In some embodiments, the metal-containing compound can have the formula: LiMPO4,where M is a metal selected from one or more of manganese, iron, cobalt, nickel, copper, zinc, magnesium, calcium and combinations thereof. In some preferred embodiments, themetal containing compound is LiFePO4.In some embodiments, the metal precursor compound can be selected from one or moreof Fe2O3, Fe3O4, FeOOH, FePO4.xH2O, FePO4, Fe3(PO4)2, FeSO4.xH2O, Fe(NO3)3, Fe(CH3CO2)2, C6H8O7xFe3+.yNH3 (ammonium iron (III) citrate), C6H5FeO7 (iron (III) citrate) and Fe(C5H7O2)3(iron (III) 2,4-pentanedionate), wherein x, y are ≥0. In some embodiments, Z can be selected from one or more halides, hydroxide-containing groups and mixtures thereof. In other embodiments, Z may not be present in the metal- containing compound (i.e. where f = 0).In some embodiments, X can comprise phosphorus. For example, (XcYd)e can be a PO4and / or P2O7 moiety.In some embodiments, the pitch may be replaced or supplemented in the mixture byphytic acid (C6H18O24P6, also referred to as inositol hexaphosphate, inositolhexakisphosphate (IP6) or inositol polyphosphate), which may act as both a phosphorusand carbon source. The phytic acid may be pyrolyzed to form a carbon coating on theparticles and agglomerates of the metal compound in the same manner as the pitch.In some embodiments, the alkali metal precursor compound may comprise an organicmoiety, such as lithium / sodium / potassium citrate, which may provide both a source ofalkali metal and carbon. In these embodiments, the organic moiety may replace orsupplement the pitch in the method.The heating step b) of the method can include heating the mixture at a temperatureproximate to or above the melting point of the pitch. This can facilitate coating of theparticles of the precursor material as the pitch melts. The temperature proximate to orabove the melting point of the pitch can vary depending on the type and composition ofthe pitch used. For example, the temperature can be in the range of 50 °C to 250 °C, suchas 70 °C to 100 °C, or 100 °C to 200 °C depending on the composition and viscosity ofthe pitch. The heating step b) can be performed in one or more stages. For example, the mixturecan be heated at a first temperature that is sufficient to melt the pitch and coat theparticles of the precursor material. This can ensure a uniform distribution of the pitch onthe surface of the particles and prevent agglomeration. Optionally, the first temperaturecan be in the range of 50 °C to 250 °C, preferably 100 °C to 200 °C, depending on thetype and composition of the pitch. The duration of heating at the first temperature can vary depending on the amount and size of the mixture, but can be in the range of 1 to 100 minutes, such as 10 to 90 minutes, 20 to 80 minutes, 30 to 70 minutes, 40 to 60 minutes, or in a range constituted by any two of the aforementioned minute values. After heating at the first temperature, the mixture can be heated at a second temperaturethat is sufficient to convert the pitch to carbon (i.e. pyrolysis). This can result in theformation of a carbon layer on the surface of the particles, which can improve the electrical conductivity and stability of the electrode material. Optionally, the second temperature can be in the range of 300 °C to 1500 °C, depending on the type and composition of thepitch and precursor material. In some embodiments, the temperature range may be from300 °C to 1200 °C, from 300 °C to 900 °C, from 500 °C to 800 °C, from 600 °C to 800 °C, or in a range constituted by any two of the aforementioned temperature values. The heating may comprise a ramped increase in temperature, for example, at a heating rateof 1 °C to 10 °C / min, 2 °C to 8 °C / min, 3 °C to 7 °C / min, 4 °C to 6 °C / min, or about 5°C / min. The temperature may be ramped until the desired temperature is reached, afterwhich the heating may be maintained at that temperature. The duration of heating at thesecond temperature can vary depending on the amount and size of the particles in themixture but can be in the range of 1 to 500 minutes, such as 10 to 450 minutes, 50 to400 minutes, 100 to 350 minutes, 200 to 350 minutes, 250 to 350 minutes, or in a rangeconstituted by any two of the aforementioned minute values. In some embodiments, the first heating temperature may be dispensed with and themixture heated at the second heating temperature, or ramped temperature, only.At least part of the pitch is converted to elemental carbon during heating at the secondtemperature. For example, at least part of the pitch is converted to sp2 hybridized carbon,which can have a higher electrical conductivity and a lower resistance than other forms ofcarbon. The conversion of the pitch to sp2 carbon can be influenced by the temperatureand duration of heating at the second temperature. At least part of the sp2 carbon can begraphitic, in which it can be described as “graphitic sp2hybridised carbon” or “networkedsp2 hybridised carbon". Graphitic carbon encompasses forms of carbon which includegraphene, carbon nanotubes, graphite, graphene char, and other forms of carbon in whichregions of honeycomb arrangements of sp2 carbon atoms exist. At least part of the pitchcan be converted to a graphene-like honeycomb network. The sp2 carbon, and degree ofconversion thereto, can be detected by Raman spectroscopy. As shown in Figure 3, the characteristic peak signals occur at around 1300-1375 cm-1(depending on incident Ramanlaser wavelength) (the “D peak”) and ~1590 cm-1 (the “G peak”). The existence, energy,width and relative intensities of these peaks permit an analysis of the presence and natureof the sp2 carbon in the material. The G peak arises from an asymmetric stretch in sp2bonded carbon networks (such as bonds in graphite) and the D peak arises from a breathing vibration of a graphitic hexagonal ring. As such, their presence in Ramantogether evidence the formation of graphitic sp2 carbon. The D / G ratio can be used toqualitatively indicate the amount of disorder. The width of the G peak is another indicator of disorder (narrower = less disorder) that correlates with higher conductive carbons. After carbothermal reduction with a polymer, the presence of strong D and G peaks indicatesconversion of the polymer carbon to graphitic sp2 carbon. An analytical method that canbe used to detect sp2 carbons by Raman spectroscopy has been published in Ferrari et al,Raman spectroscopy as a versatile tool for studying the properties of graphene, NatureNanotech 8, 235–246 (2013), and Ferrari et al, Interpretation of Raman spectra ofdisordered and amorphous carbon, Phys. Rev. B 61, 14095 (2000), both of which areincorporated herein by reference. The thickness of the coating on the particles or agglomerates of metal compound may beless than 100 nm, less than 75 nm, less than 50 nm, less than 20 nm, less than 10 nm,or in a range between any two of the aforementioned values. Preferably the coating has athickness of less than 10 nm. Measurement of the thickness can be performed bytransmission electron microscopy (TEM), by visual analysis of a TEM image, for instance, as shown in Figure 2.The mixture may further comprise particulate carbon and / or one or more carbon-containing polymer(s) in addition to the pitch. The particulate carbon may be any form ofcarbon that has a small size and a high surface area, such as carbon black, activated carbon, carbon nanotubes, graphene, or a combination thereof. The particulate carbonmay have an average particle size, as measured by laser diffraction analyser, of less than1 μm, such as less than 500 nm, less than 200 nm, less than 100 nm, or less than 50 nm.The particulate carbon may have a Brunauer-Emmett-Teller (BET) surface area of greaterthan 5 m2 / g, such as greater than 10 m2 / g, 50 m2 / g, greater than 100 m2 / g, greater than200 m2 / g, greater than 500 m2 / g, greater than 1000 m2 / g, or a combination thereof, orin a range between any two of the aforementioned values. The particulate carbon may beC65, which has a surface area of around 65 m2 / g, or C45, which has a surface area ofaround 45 m2 / g. Brunauer-Emmett-Teller (BET) surface area analysis is a multi-pointmeasurement of an analyte's specific surface area (m2 / g) through gas adsorption analysis, where an inert gas such as nitrogen is continuously flowed over a solid sample, or the solid sample is suspended in a defined gaseous volume. The particulate carbon may be added to the mixture before, during, or after the addition of the pitch. The amount of the particulate carbon may range from 0.1 wt% to 50 wt%, such as 2% to 50%, 2.5% to 50%, 5% to 50%, 2.5% to 20%, 0.1 wt% to 20 wt%, 0.5 wt% to 15 wt%, 1 wt% to 10 wt%, 2 wt% to 8 wt%, 3 wt% to 6 wt%, 4 wt% to 5 wt%, or in a range constituted by any two of the aforementioned weight percentages, based on the based on the combinedweight of the pitch and particulate carbon. Preferably, the amount of particulate carbon isfrom 2.5% to 20%, more preferably from 5% to 20%, based on the combined weight of the pitch and particulate carbon. The particulate carbon can act as a conductive filler that enhances the electrical conductivity and stability of the electrode material. The particulate carbon can connect the metal particles together into an interconnected network that facilitates the transport of electrons within the material. The particulate carbon can also improve the mechanical strength and integrity of the electrode material by bridging the gaps between the metal particles and reducing stress concentration. The particulate carbon can further increase the specific capacity and rate performance of the electrodematerial. Importantly, the particulate carbon can improve the tap density andcompressibility of the carbon-coated metal-containing compound, as shown in Figures 25to 27. Higher tap density and higher compressibility are desirable properties because theyproduce electrode material of a higher energy density. It is unexpected that the additionof particulate carbon to the reaction mixture in step a) would enhance tap density or compressibility because particulate carbon has a high surface area and low density. For example, the bulk density of particulate carbon is typically in the range of about 0.05 to0.25 g / cc. Therefore, it is unexpected that the combination of such a light material with adense material such as pitch would produce a higher tap density. Furthermore, a largeincrease in tap density is usually associated with a reduction in specific capacity. Therefore, it is also advantageously unexpected that the combination of a pitch and particulate carbon in the coating would result in a high increase in tap density without a significant reductionin specific capacity (as shown in Figures 25 to 27). The optimum quantity of particulatecarbon in the coating is from 10% to 30%, from 15% to 25%, or about 20%, based onthe combined weight of the pitch and particulate carbon. Without wishing to be bound bytheory, a possible explanation for this “sweet spot” may be that it is the point at whichnucleation is optimised. At lower quantities of particulate carbon, there may be insufficientnucleation sites to which the pitch can attach, whereas at higher quantities of particulatecarbon there may be insufficient quantities of pitch to nucleate around the carbon particles. The carbon-containing polymer may be selected from the group consisting of polyethylene(PE), HMPE (high modulus PE), HDPE (high density PE), LDPE (low density polyethylene)polypropylene (PP), HMPP (high modulus PP), HDPP (high density PP), LDPP (low densitypolypropylene), polyvinylchloride (PVC), polyethylene terephthalate (PET), polystyrene (PS), polyethylene glycol (PEG), polyvinylidene fluoride (PVdF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), polyacrylonitrile (PAN), polyvinyl alcohol (PVA),polytetrafluoroethylene (PTFE), polycarbonates, nylon, and combinations thereof.Preferably, the polymer has a high carbon content, such as polyethylene, polypropylene, high modulus polyethylene and high modulus polypropylene. Optionally, the polymer may be in particulate form. Optionally the polymer may be waste polymer, such as recycled plastic waste. The carbon-containing polymer may be an elastomer obtained from rubber. Optionally, the rubber may be tyre rubber, such as de-vulcanized tyre rubber. Tyre rubber also containsparticulate carbon in the form of carbon black.The particulate carbon and polymer may be present in the composition in a mass ratio of from 10:90 to 90:10, from 25:75 to 75:25, from 40:60 to 60:40, or about 50:50 with respect to each other. The pitch and carbon-containing polymer may be present in the composition in a mass ratio of from 10:90 to 90:10, from 25:75 to 75:25, from 40:60 to 60:40, or about 50:50 with respect to each other. The method may use a stoichiometric excess of carbon in the reaction with respect to themetal precursor compound(s). The carbon originates from the pitch and optionally fromother carbon sources such as the particulate carbon and carbon-containing polymer. Theexcess carbon may be based on the assumption of a C --> CO carbothermal reaction. Themethod may provide a carbon-coated metal-containing compound having a total carbon content of from 0.5 to 10 %, 0.5 to 5 %, 1 to 5%, 1 to 4%, or 3 to 4% by weight carbon (with the remaining wt% made up of the metal-containing compound). Preferably, the carbon-coated metal-containing compound has a total carbon content of from 1 to 5% by weight carbon. The present invention extends to an electrode active material containing the carbon-coated metal-containing compound made according to the above method. The electrode active material can form a cathode of a battery, such as a secondary or rechargeable battery. The battery can preferably be an alkali metal ion battery, such as a lithium-ion battery or a sodium-ion battery. Rechargeable batteries typically comprise an anode, a cathode, a separator, and anelectrolyte. The anode is the negative electrode that releases electrons to an externalcircuit during discharge and the cathode is the positive electrode that receives electronsfrom the external circuit during discharge. The separator is typically a porous membranethat prevents direct contact between the anode and the cathode while allowing the passageof ions therebetween. The electrolyte is a liquid, solid, or gel medium that facilitates thetransport of ions between the anode and the cathode. The cathode material can be applied to a current collector to form a cathode layer. The current collector can be any electrically conductive material that can collect the electrons from the cathode and deliver them to the external circuit. Examples of suitable current collectors include, but are not limited to, aluminium, nickel, stainless steel, copper, carbon, or a combination thereof. The current collector can have any shape or form, such as a foil, a sheet, a mesh, a wire, a rod, or a tube. The cathode layer can be coated, laminated, pressed, or bonded to the current collector by any suitable method, such as spray coating, dip coating, slot-die coating, doctor blade coating, roll-to-roll coating, electroplating, sputtering, thermal evaporation, chemical vapor deposition, physical vapor deposition, or a combination thereof. The thickness of the cathode layer can vary depending on the desired capacity and power density of the battery, and can range from 1 μm to 500 μm, such as 5 μm to 200 μm, 10 μm to 100 μm, 20 μm to 80 μm, 30 μm to 60 μm, 40 μm to 50 μm, or in a range constituted by any two of the aforementioned values. Similarly, the anode material can be applied to a current collector to form an anode layer. The current collector can be any electrically conductive material that can collect the electrons from the external circuit and deliver them to the anode. Examples of suitable current collectors include, but are not limited to, copper, nickel, stainless steel, aluminium, carbon, or a combination thereof. The current collector can have any shape or form, such as a foil, a sheet, a mesh, a wire, a rod, or a tube. The anode layer can be coated, laminated, pressed, or bonded to the current collector by any suitable method, such as spray coating, dip coating, slot-die coating, doctor blade coating, roll-to-roll coating, electroplating, sputtering, thermal evaporation, chemical vapor deposition, physical vapor deposition, or a combination thereof. The thickness of the anode layer can vary depending on the desired capacity and power density of the battery, and can range from 1 μm to 500 μm, such as 5 μm to 200 μm, 10 μm to 100 μm, 20 μm to 80 μm, 30 μm to 60 μm, 40 μm to 50 μm, or in a range constituted by any two of the aforementioned values. The electrolyte can comprise a solvent, a salt, and optionally an additive. The solvent can be any organic or inorganic compound that can dissolve the salt and provide sufficient conductivity and stability for the battery operation. Examples of suitable solvents include, but are not limited to, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, gamma-butyrolactone, tetrahydrofuran, 2- methyltetrahydrofuran, dimethoxyethane, diethoxyethane, sulfolane, acetonitrile, dimethylformamide, dimethylsulfoxide, water, or a combination thereof. The salt can be any alkali metal salt that can provide the cations for the battery operation. Examples of suitable salts include, but are not limited to, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium triflate, lithium bis(oxalato)borate, lithium hexafluoroarsenate, lithium iodide, sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(trifluoromethanesulfonyl)imide, sodium triflate, sodium bis(oxalato)borate, sodium hexafluoroarsenate, sodium iodide, or a combination thereof. The additive can be any compound that can improve the performance and safety of the battery, such as by enhancing the conductivity, stability, and compatibility of the electrolyte, or by forming aprotective layer on the electrode surface. The amount of the solvent, the salt, and theadditive can vary depending on the desired viscosity, conductivity, and electrochemicalproperties of the electrolyte.The invention will now be described in further detail with reference to the following non- limiting examples. EXAMPLES Synthesis General Method 1. The starting materials are intimately mixed in the correct stoichiometric proportionsand pressed into a pellet. 2. The resulting pelletized mixture is placed in a crucible that is then placed inside afurnace under an inert atmosphere at a furnace temperature of between 300°C and 900°C until a product is formed. 3. The product is allowed to cool under an inert atmosphere before grinding to apowder. Abbreviationsxs = excess over the stoichiometric reactionRMM = relative molecular mass Product Analysis using powder X-ray Diffraction (XRD) Analysis by XRD was conducted using a Bruker D2 Phaser powder XRD diffractometer to confirm that the desired target materials had been prepared, to establish the phase purity of the product, and to determine the type of impurities that may be present. The XRD operating conditions are as follows: X-ray source: CuKαX-ray wavelength: 1.5418 ÂTypical 2θ range: 2θ = 10 to 65o with a 0.0202 degrees 2θ step sizeTap and Compressed DensityFor tap density measurements, the volume of a ~3.5 g sample was measured after 200taps in a 10 mL cylinder. The exact sample mass was divided by the volume.For compressed density measurement, the volume of a ~2.5 g pellet formed under2500psi in a 20 mm die was measured after the die pressure was removed. The exactpellet mass was divided by the pellet volume. Electrochemical Results The target materials were tested in metallic lithium half cells which can be made using thefollowing procedure. The materials synthesized (active materials) were made into positiveelectrodes. The positive electrode was prepared by solvent casting a slurry of the activematerial, conductive carbon, binder and binder solvent. The conductive carbon used wasC65 (Imerys). PVdF-HFP co-polymer (Sigma-Aldrich) was used as the binder and acetonewas employed as the binder solvent. The slurry was then cast into a glass plate and a free-standing electrode was formed as the solvent evaporates. The electrode was then driedfurther at 80oC in an oven in an air atmosphere. The dried positive electrode composition comprised 80 % active material, 8 % C65 carbon and 12 % PVdF-HFP binder. Optionally an aluminium current collector or a carbon coated aluminium current collector may beused as the contact to the active material. Metallic lithium was used as the negativeelectrode material. Optionally a copper current collector may be used as the contact to the lithium material. The electrolyte comprises a battery grade 1M solution of LiPF6 in ethylene carbonate (EC) and diethyl carbonate (DEC) in a weight ratio of 1:1. Alternatively an electrolyte may comprise a battery grade 1M solution of LiPF6 in ethylene carbonate (EC) and propylene carbonate (PC). There may also be electrolyte additives. A glass fibre separator (Whatman GF / A grade) or a porous polypropylene or porous polyethylene (e.g.,Celgard 2400) wetted by the electrolyte, was interposed between the positive and negativeelectrodes.The cells were tested as follows. The cells were tested at room temperature. For constantcurrent cycling, the cell was cycled at a given (low rate) current density between pre-setvoltage limits. A commercial battery cycler was used (for example, from Neware®, China).On charge, lithium ions were extracted from the cathode active material while on subsequent discharge lithium ions were re-inserted into the cathode active material. Thismethod provided a voltage (versus the Li reference potential) versus specific capacityprofile for the active material under investigation. This approach may be extended over multiple charge-discharge cycles to provide a long-term cycle stability test. Alternatively, the cells were tested using the electrochemical voltage spectroscopy (EVS) technique, as described in (1) Barker et al, Electrochimica Acta, vol. 41, No. 16, pp. 2639-2646, 1996; (2) Barker et al, Synthetic Metals, 28 (1989), D127-D134, and (3) Barker,Electrochimica Acta, vol. 40, no. 11, pp. 1603-1608, 1995, all of which are incorporatedherein by reference. EVS is a voltage step method which provides a high-resolutionapproximation to the open circuit voltage curve (versus the Li reference potential) for the electrochemical system under investigation. Similarly to the constant current testing, thisEVS method provided a voltage (versus the Li reference potential) versus specific capacityprofile for the active material under investigation. The complementary differential capacitydata had been demonstrated to allow effective characterisation of polarization, order-disorder and structural ordering phenomena in intercalation systems. The EVS testing was carried out using custom software and commercial voltage generator (Advantest) and current monitoring equipment (Hewlett Packard). Raman SpectroscopyThe incident laser wavelength was 785 nm. The laser power was 3 mW. 25 spectra werecollected over an area 80x80 µm at points spaced by 20 µm in x and y (the map of points)using a Renishaw Raman spectrometer. The intensity ratio of D and G peaks (D / G) was calculated for each Raman spectrum by first identifying D and G peak maxima by a localmaximum finding algorithm. The average and standard deviation of D / G of all points inthe map was reported. COMPARATIVE EXAMPLE 1 Using Particulate Carbon only (C65). LiH2PO4 / Fe2O3 / C65 particulate carbon Synthesis Number: R1001 Material Synthesis Synthesis Stoichiometric Reaction:LiH2PO4 + 0.5 Fe2O3 + 0.5 C ^ LiFePO4 + H2O + 0.5 CO2 Synthesis Precursor Recipe: LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g Fe2O3 [RMM = 159.7 g / mol] (g): 0.7985 g Carbon: C65; 0.12 gMixing Conditions: McCrone Micronizer, 20 mins Agate Media; Sample pelletized.Furnace Ramp rate, Temperature, Dwell, Ambient gas: 5oC / min, 725oC, 5 hours, N2By design an excess of the carbon source (in this case, particulate carbon C65) was usedto ensure that a composite material product was formed comprising the active materialand the excess carbon.Figure 4 shows the XRD data for the sample of Comparative Example 1. From inspectionwe detected that the sample was close to phase pure LiFePO4.Figure 5 shows the constant current data for the LiFePO4 cathode active material ofComparative Example 1. As shown in Figure 5, during the charge process (lithium extraction from the LiFePO4) a charge equivalent to 115 mAh / g was obtained for the cathode active material. The subsequent discharge process (lithium re-insertion into theLiFePO4) corresponded to a reversible material specific capacity of 107 mAh / g, indicatinga reasonable lithium insertion / extraction cycle. The theoretical specific capacity for LiFePO4is approximately 170 mAh / g (assuming cycling of one lithium ion per LiFePO4 formula unit). The 107 mAh / g corresponds to (107 / 170) x 100 % (i.e. an active material utilization of about 63 %). This represents a reasonable overall performance for this LiFePO4active material. EXAMPLE 1 Using CTP only (CTP = Coal Tar Pitch). Li2CO3 / Anhydrous FePO4 / CTP / 725oC Synthesis Number: R1124 Material Synthesis Synthesis Stoichiometric Reaction:0.5 Li2CO3 + FePO4 + 0.5 0.5 CO2 + 0.5COLi2CO3[RMM = 73.9 g / mol] (g): 0.37 g Anhydrous FePO4 SAMPLE TSAKER NE-GR-6. [RMM = 150.8 g / mol] (g): 1.508 g Carbon (% mass excess = 100%) Coal Tar Pitch: [RMM = 12.0 g / mol] (g): 0.12 gPellet mix used: 4.5 g total -- Li2CO3 = 0.833 g, FePO4 = 3.396 g, CTP = 0.270 gMixing Conditions: (using Retsch Mixer Mill 500, MM500), 30 mins, 30 Hz; Sample pelletized. Furnace Ramp rate, Temperature, Dwell, Ambient gas: 5o / min, 725oC, 5 hours, N2By design an excess of the carbon source (derived from CTP) was used to ensure that acomposite material product was formed comprising the active material and the excesscarbon.Figure 6 shows the XRD data for the sample of R1124. From inspection it was detectedthat the sample was close to phase pure LiFePO4. There were no XRD reflections fromextraneous impurities.Figure 7 shows the constant current data for the LiFePO4 cathode active material ofExample 1, R1124. Referring to Figure 7, during the charge process (lithium extractionfrom the LiFePO4) a charge equivalent to 174 mAh / g was obtained for the cathode activematerial. This is in excess of the theoretical specific capacity for LiFePO4 and thisphenomenon was due to some electrolyte degradation (oxidation) processes during cellcharge. The subsequent discharge process (lithium re-insertion into the LiFePO4)corresponded to a reversible material specific capacity of 158 mAh / g, indicating anexcellent lithium insertion / extraction cycle. The theoretical specific capacity for LiFePO4 is approximately 170 mAh / g (assuming cycling of one lithium ion per LiFePO4formula unit).The 158 mAh / g corresponds to (158 / 170) x 100 % (i.e. an active material utilization ofabout 93 %). This represents a reasonable overall performance for this LiFePO4 active material. EXAMPLE 2 Using CTP and HMPE (CTP = Coal Tar Pitch, HMPE = high modulus polyethylene powder). Li2CO3 / Anhydrous FePO4 / CTP / HMPE / 725oC Synthesis Number: R1125 Material Synthesis Synthesis Stoichiometric Reaction:0.5 Li2CO3 + FePO4 + 0.5 0.5 CO2 + 0.5COLi2CO3[RMM = 73.9 g / mol] (g): 0.37 g Anhydrous FePO4SAMPLE TSAKER NE-GR-6. [RMM = 150.8 g / mol] (g): 1.508 g Carbon [RMM = 12 g / mol] (% mass excess = 100%) CARBON 1: Coal tar pitch (assume 100% carbon): [RMM = 12.0 g / mol] (g): 0.06g CARBON 2: HMPE35A (Goonvean): (PE = 86 w / o carbon = 0.5 x (0.12 / 0.86) = 0.0698 gPellet mix 4.5 g -- Li2CO3 = 0.829 g, FePO4 = 3.380 g, CTP = 0.134 g, HMPE = 0.156 g Mixing Conditions: (using Retsch Mixer Mill 500, MM500), 30 mins, 30 Hz; Sample pelletized. Furnace Ramp rate, Temperature, Dwell, Ambient gas: 5o / min, 725oC, 5 hours, N2 By design an excess of the carbon source (in this case, derived from CTP and HMPE) wasused to ensure that a composite material product was formed comprising the activematerial and the excess carbon.Figure 8 shows the XRD data for the sample R1125. From inspection it was detected thatthe sample was close to phase pure LiFePO4. There were no XRD reflections fromextraneous impurities.Figures 9 and 10 show the Electrochemical Voltage Spectroscopy data for the LiFePO4sample R1125.Figure 9 shows the EVS voltage profile for the LiFePO4 cathode active material R1125(made using Li2CO3, FePO4, CTP and HMPE). Figure 9 shows the EVS voltage profile(electrode potential versus specific capacity) for cycle 2. The current density cut-off ateach EVS voltage step was set so that the EVS cycle was equivalent to a constant currentcycle rate of approximately C / 10 assuming a reversible specific capacity of 150 mAh / g forthe active material (where a 1 C rate is a rate equivalent to a 1-hour charge and a 1-hourdischarge). Referring to Figure 9, during the charge process (lithium extraction from the LiFePO4) acharge equivalent to 168 mAh / g was obtained for the cathode active material. Thesubsequent discharge process (lithium re-insertion into the LiFePO4) corresponded to areversible material specific capacity of 158 mAh / g, indicating an excellent lithiuminsertion / extraction cycle. The theoretical specific capacity for LiFePO4is approximately 170 mAh / g (assuming cycling of one lithium ion per LiFePO4formula unit). Thus the 158 mAh / g corresponds to (158 / 170) x 100 % (i.e. an active material utilization of about 93 %). This represents excellent overall performance for this LiFePO4 active material.Referring to Figure 10 the differential capacity data for LiFePO4 sample is denoted R1125.The generally symmetrical nature of the differential capacity data on charge (above the x axis) and the corresponding differential capacity data on discharge (below the x axis) indicates the excellent reversibility of the lithium extraction / insertion behaviour in this LiFePO4material. EXAMPLE 3 Using CTP and particulate carbon, ENSACO 250G (CTP = Coal Tar Pitch). Li2CO3 / Anhydrous FePO4 / CTP / Ensaco250G / 725oC Synthesis Number: R1126 Material Synthesis Synthesis Stoichiometric Reaction:0.5 Li2CO3 + FePO4 + 0.5 0.5 CO2 + 0.5COLi2CO3 [RMM = 73.9 g / mol] (g): 0.37 g Anhydrous FePO4 SAMPLE TSAKER NE-GR-6. [RMM = 150.8 g / mol] (g): 1.508 g Carbon [RMM = 12 g / mol] (% mass excess = 100%) CARBON 1: Coal tar pitch (assume 100% carbon): [RMM = 12.0 g / mol] (g): 0.06g CARBON 2: ENSACO 250 G : [RMM = 12.0 g / mol] (g): 0.06 gPellet mix 4.5 g -- Li2CO3 = 0.833 g, FePO4 = 3.396 g, CTP = 0.135 g, ENSACO = 0.135gMixing Conditions: (using Retsch Mixer Mill 500, MM500), 30 mins, 30 Hz; Sample pelletized. Furnace Ramp rate, Temperature, Dwell, Ambient gas: 5o / min, 725oC, 5 hours, N2By design an excess of the carbon source (in this case, derived from CTP and particulatecarbon, Ensaco 250G) was used to ensure that a composite material product was formedcomprising the active material and the excess carbon.Figure 11 shows the XRD data for the sample of R1126. From inspection it was detectedthat the sample was close to phase pure LiFePO4.Figure 12 shows the constant current data for the LiFePO4 cathode active material ofR1126. As shown in Figure 12, during the charge process (lithium extraction from theLiFePO4) a charge equivalent to 161 mAh / g was obtained for the cathode active material.The subsequent discharge process (lithium re-insertion into the LiFePO4) corresponded toa reversible material specific capacity of 158 mAh / g, indicating a reasonable lithiuminsertion / extraction cycle. The theoretical specific capacity for LiFePO4 is approximately170 mAh / g (assuming cycling of one lithium ion per LiFePO4 formula unit). The 158 mAh / gcorresponds to (158 / 170) x 100 % (i.e. an active material utilization of about 93 %). This represents a reasonable overall performance for this LiFePO4active material. EXAMPLE 4 Using CTP and HMPE (CTP = Coal Tar Pitch HMPE = high modulus polyethylene powder). Li2CO3 / Anhydrous FePO4 / CTP / HMPE / 725oC - Different ratio of CTP to HMPMCTP:HMPE (25:75) approx. (by mass estimate of carbon)Synthesis Number: R1145 Material Synthesis Synthesis Stoichiometric Reaction:0.5 Li2CO3 + FePO4 + 0.5 0.5 CO2 + 0.5 COLi2CO3 [RMM = 73.9 g / mol] (g): 0.37 gAnhydrous FePO4SAMPLE TSAKER NE-GR-6. [RMM = 150.8 g / mol] (g): 1.508 g Carbon [RMM = 12 g / mol] (% mass excess = 100%) CARBON 1: Coal tar pitch: [RMM = 12.0 g / mol] (g): 0.25*0.06 = 0.015 gCARBON 2: HMPE35A (Goonvean) : (PE = 86 wt% carbon = 0.75 x (0.12 / 0.86) = 0.105gPellet mix 4.5 g -- Li2CO3 = 0.829 g, FePO4 = 3.380 g, CTP = 0.0338 g, HMPE = 0.236 gMixing Conditions: (using Retsch Mixer Mill 500, MM500), 30 mins, 30 Hz; Sample pelletized. Furnace Ramp rate, Temperature, Dwell, Ambient gas: 5o / min, 725oC, 5 hours, N2By design an excess of the carbon source (in this case, derived from CTP and HMPE) wasused to ensure that a composite material product was formed comprising the activematerial and the excess carbon.Figure 13 shows the XRD data for the sample R1145. From inspection it was detected thatthe sample was close to phase pure LiFePO4. There were no XRD reflections fromextraneous impurities.Figures 14 and 15 show the Electrochemical Voltage Spectroscopy data for the LiFePO4sample R1145.Figure 14 shows the EVS voltage profile for the LiFePO4 cathode active material R1145(made using Li2CO3, FePO4, CTP and HMPE). Figure 14 shows the EVS voltage profile(electrode potential versus specific capacity) for cycle 2. The current density cut-off ateach EVS voltage step was set so that the EVS cycle was equivalent to a constant currentcycle rate of approximately C / 10 assuming a reversible specific capacity of 150 mAh / g forthe active material (where a 1 C rate is a rate equivalent to a 1-hour charge and a 1-hourdischarge). Referring to Figure 14, during the charge process (lithium extraction from the LiFePO4) acharge equivalent to 180 mAh / g was obtained for the cathode active material. This is inexcess of the theoretical specific capacity for LiFePO4 and this phenomenon was due tosome electrolyte degradation (oxidation) processes during cell charge. The subsequentdischarge process (lithium re-insertion into the LiFePO4) corresponded to a reversiblematerial specific capacity of 169 mAh / g, indicating an excellent lithium insertion / extraction cycle. The theoretical specific capacity for LiFePO4is approximately 170 mAh / g (assumingcycling of one lithium ion per LiFePO4 formula unit). Thus the 169 mAh / g corresponds to(169 / 170) x 100 % (i.e. an active material utilization of about 100 %). This representsexcellent overall performance for this LiFePO4 active material.Referring to Figure 15 we denote the differential capacity data for LiFePO4 sample R1145.The generally symmetrical nature of the differential capacity data on charge (above the xaxis) and the corresponding differential capacity data on discharge (below the x axis) indicates the excellent reversibility of the lithium extraction / insertion behaviour in this LiFePO4material. EXAMPLE 5 Using CTP and HMPE (CTP = Coal Tar Pitch HMPE = high modulus polyethylene powder).Li2CO3 / Anhydrous FePO4 / CTP / HMPE / 725oC - Different ratio of CTP to HMPECTP:HMPE (75:25) approx. (by mass estimate of carbon)Synthesis Number: R1146Material Synthesis Synthesis Stoichiometric Reaction:0.5 Li2CO3 + FePO4 + 0.5 0.5 CO2 + 0.5 COLi2CO3[RMM = 73.9 g / mol] (g): 0.37 g Anhydrous FePO4 SAMPLE TSAKER NE-GR-6. [RMM = 150.8 g / mol] (g): 1.508 g Carbon [RMM = 12 g / mol] (% mass excess = 100%)CARBON 1: Coal tar pitch (assume 100% carbon) : [RMM = 12.0 g / mol] (g):0.75*12*0.005 = 0.045 gCARBON 2: HMPE35A (Goonvean): (PE = 86 wt% carbon = 0.25 x (0.12 / 0.86) = 0.035 gPellet mix 4.5 g -- Li2CO3 = 0.829 g, FePO4 = 3.380 g, CTP = 0.103 g, HMPE = 0.08 gMixing Conditions: MM500, 30 mins, 30 Hz; sample pelletized. Furnace Ramp rate, Temperature, Dwell, Ambient gas: 5o / min, 725oC, 5 hours, N2By design an excess of the carbon source (in this case, derived from CTP and HMPE) wasused to ensure that a composite material product was formed comprising the activematerial and the excess carbon.Figure 16 shows the XRD data for the sample of R1146. From inspection it was detectedthat the sample was close to phase pure LiFePO4.Figure 17 shows the constant current data for the LiFePO4 cathode active material ofR1146. As shown in Figure 17 during the charge process (lithium extraction from theLiFePO4) a charge equivalent to 167 mAh / g was obtained for the cathode active material.The subsequent discharge process (lithium re-insertion into the LiFePO4) corresponded toa reversible material specific capacity of 140 mAh / g, indicating a reasonable lithiuminsertion / extraction cycle. The theoretical specific capacity for LiFePO4 is approximately170 mAh / g (assuming cycling of one lithium ion per LiFePO4 formula unit). The 140 mAh / gcorresponds to (140 / 170) x 100 % (i.e. an active material utilization of about 82 %). Thisrepresents a reasonable overall performance for this LiFePO4active material. EXAMPLE 6Using LiH2PO4, FeOOH precursor and CTP only.LiH2PO4 / FeOOH / CTP Synthesis Number: R1162 Material Synthesis Synthesis Stoichiometric Reaction:LiH2PO4 + 1.0 FeOOH + 0.5 C ^ LiFePO4 + 2.0 H2O + 0.5 COLiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g Lanxess FeOOH [RMM = 88.9 g / mol] (g): 0.889 g Carbon CTP [RMM = 12 g / mol] (% mass excess = 100%) : 0.12 g Pellet mix 4.5 g: LiH2PO4 = 2.283 g, FeOOH = 1.953 g, CTP = 0.336 g Mixing Conditions: MM500, 30 mins, 30 Hz; Sample pelletized. Polyethylene Powder HMPE35A (Goonvean) (PE = 86 w / o carbon = 1.0 x (0.12 / 0.86) = 0.140 g. Furnace Ramp rate, Temperature, Dwell, Ambient gas: 5o / min, 725oC, 5 hours, N2By design an excess of the carbon source (in this case, derived from CTP) was used toensure that a composite material product was formed comprising the active material andthe excess carbon.Figure 18 shows the XRD data for the sample R1162. From inspection it was detected thatthe sample was close to phase pure LiFePO4. There were no XRD reflections fromextraneous impurities.Figures 19 and 20 show the Electrochemical Voltage Spectroscopy data for the LiFePO4sample R1162.Figure 19 shows the EVS voltage profile for the LiFePO4 cathode active material R1162(made using LiH2PO4 / FeOOH / CTP). Figure 19 shows the EVS voltage profile (electrodepotential versus specific capacity) for cycle 1. The current density cut-off at each EVS voltage step was set so that the EVS cycle was equivalent to a constant current cycle rate of approximately C / 10 assuming a reversible specific capacity of 150 mAh / g for the active material (where a 1 C rate is a rate equivalent to a 1-hour charge and a 1-hour discharge). Referring to Figure 19, during the charge process (lithium extraction from the LiFePO4) acharge equivalent to 156 mAh / g was obtained for the cathode active material. Thesubsequent discharge process (lithium re-insertion into the LiFePO4) corresponded to areversible material specific capacity of 143 mAh / g, indicating an excellent lithiuminsertion / extraction cycle. The theoretical specific capacity for LiFePO4 is approximately 170 mAh / g (assuming cycling of one lithium ion per LiFePO4formula unit). Thus the 143 mAh / g corresponds to (143 / 170) x 100 % (i.e. an active material utilization of about 84 %). This represents excellent overall performance for this LiFePO4 active material.Referring to Figure 20 we denote the differential capacity data for LiFePO4 sample R1162.The generally symmetrical nature of the differential capacity data on charge (above the x axis) and the corresponding differential capacity data on discharge (below the x axis) indicates the excellent reversibility of the lithium extraction / insertion behaviour in this LiFePO4 material. EXAMPLE 7 Using FeOOH with CTP and HMPE LiH2PO4 / FeOOH / CTP + HMPE Synthesis Number: R1163 Material Synthesis Synthesis Stoichiometric Reaction:LiH2PO4 + 1.0 FeOOH + 0.5 C ^ LiFePO4 + 2.0 H2O + 0.5 COLiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g Lanxess FeOOH [RMM = 88.9 g / mol] (g): 0.889 g mol Carbon [RMM = 12 g / mol] (% mass excess = 100%)CARBON 1: Coal tar pitch (assume 100% carbon) : [RMM = 12.0 g / mol] (g): 12*0.005 =0.06 g CARBON 2: HMPE35A (Goonvean): (PE = 86 w / o carbon = 0.005 x (12 / 0.86) = 0.07 g. Pellet mix 4.5 g: LiH2PO4 = 2.272 g, FeOOH = 1.944 g, CTP = 0.131 g, PE = 0.153 g Mixing Conditions: MM500, 30 mins, 30 Hz; Sample pelletized. Polyethylene Powder HMPE35A (Goonvean) (PE = 86 w / o carbon = 1.0 x (0.12 / 0.86) = 0.140 g. Furnace Ramp rate, Temperature, Dwell, Ambient gas: 5o / min, 725oC, 5 hours, N2By design an excess of the carbon source (in this case, derived from CTP and HMPE) wasused to ensure that a composite material product was formed comprising the activematerial and the excess carbon.Figure 21 shows the XRD data for the sample R1163. From inspection we detected thatthe sample was close to phase pure LiFePO4. There were no XRD reflections from extraneous impurities.Figures 22 and 23 show the Electrochemical Voltage Spectroscopy data for the LiFePO4sample R1163.Figure 22 shows the EVS voltage profile for the LiFePO4 cathode active material R1163(made using LiH2PO4 / FeOOH / CTP + HMPE). Figure 22 shows the EVS voltage profile(electrode potential versus specific capacity) for cycle 1. The current density cut-off at each EVS voltage step was set so that the EVS cycle was equivalent to a constant current cycle rate of approximately C / 10 assuming a reversible specific capacity of 150 mAh / g forthe active material (where a 1 C rate is a rate equivalent to a 1-hour charge and a 1-hourdischarge). Referring to Figure 22, during the charge process (lithium extraction from the LiFePO4) acharge equivalent to 176 mAh / g was obtained for the cathode active material. This is inexcess of the theoretical specific capacity for LiFePO4 and this phenomenon was due tosome electrolyte degradation (oxidation) processes during cell charge. The subsequentdischarge process (lithium re-insertion into the LiFePO4) corresponded to a reversiblematerial specific capacity of 141 mAh / g, indicating an excellent lithium insertion / extractioncycle. The theoretical specific capacity for LiFePO4is approximately 170 mAh / g (assumingcycling of one lithium ion per LiFePO4 formula unit). Thus the 141 mAh / g corresponds to(141 / 170) x 100 % (i.e. an active material utilization of about 83 %). This representsexcellent overall performance for this LiFePO4 active material.Referring to Figure 23 we denote the differential capacity data for LiFePO4 sample R1163.The generally symmetrical nature of the differential capacity data on charge (above the x axis) and the corresponding differential capacity data on discharge (below the x axis) indicates the excellent reversibility of the lithium extraction / insertion behaviour in this LiFePO4material.EXAMPLE 8Lithium iron (II) phosphate (LFP) was synthesised from iron (III) oxide and lithium dihydrogen phosphate with petroleum pitch and particulate carbon sources. The general reaction scheme is: 0.5 Fe2O3 + 1 LiH2PO4 + N C → LiFePO4 + H2O + 0.5 CO Equation 1where N is 0.5 (0% excess carbon), or 0.7 (40% excess carbon).The petroleum pitch was ZL 250M (LM). Samples with blends of petroleum pitch andparticulate carbon (SuperP, Imreys) were prepared as follows: Petroleum Excess Petroleum pitch Particulate carbon pitch carbon proportion [%] proportion [%] [%] ZL 250M 0 100, 97.5, 95, 90, 80, 50 0, 2.5, 5, 10, 20, 50The following steps are carried out: (1) Pre-mix reactants in the following proportions:0.50 mol Fe2O3 79.85 g1.00 mol LiH2PO4 103.93 g0.50 mol C 6.01g(2) Pelletise powder mixture.(3) Heat the pellet to 725°C at a rate of 5°C / min under N2 atmosphere, then dwell for5 hours.(4) Cool at a rate of 2°C / min to room temperature.(5) Pulverise the cooked pellet.Characterisation ResultsFrom visual inspection of Figure 24, the XRD pattern showed a phase pure lithium iron (II)phosphate product. Figure 25 shows that the specific capacity on 2nd 0.1C cycle discharge was approximately unchanged through the series of particulate carbon proportions from0% to 20% and decreased slightly at 50% particulate carbon. As shown in Figure 26, tapdensity increased approximately linearly from 0% to 50% particulate carbon. Figure 27illustrates that compression density was higher for all samples containing particulate carbon by comparison with the sample having 0% particulate carbon. As noted above, Figure 3 illustrates the characteristic peak signals which occur at around 1300-1375 cm-1(the “D peak”) and ~1590 cm-1(the “G peak”), enabling a D / G ratio to be calculated. The D / G ratio for the comparative example (particulate carbon only as setout above) was calculated as 1.48 ± 0.05. For the compositions of Example 8, the D / Gratio was calculated as 1.31 ± 0.02. The strong D and G peaks shown in Figure 3, togetherwith a reduced D / G ratio for example 8 versus the comparative sample is a strong indicatorof high levels of conversion to sp2carbon. Other Materials The above synthesis methods may also be used to prepare the following specific compounds: LiFe0.1Mn0.9PO4, LiFe0.2Mn0.8PO4, LiFe0.3Mn0.7PO4, LiFe0.4Mn0.6PO4, LiFe0.5Mn0.5PO4, LiFe0.95Mg0.05PO4, LiFe0.9Mg0.1PO4, LiFe0.1Mg0.05Mn0.85PO4, LiFe0.2Mg0.05Mn0.75PO4, LiVPO4F, Li3V2(PO4)3, NaFePO4, NaMnPO4, and Na3V2(PO4)2F3.

Claims

CLAIMS1. A method for producing a carbon-coated metal-containing compound, the methodcomprising the steps of: a) forming a mixture comprising: i) pitch; ii) one or more alkali metal precursor compound(s); and iii) one or more metal precursor compound(s) comprising one or moremetals selected from transition metals, non-transition metals and metalloids, wherein the metal in each metal precursor compound has aninitial average oxidation state; and b) heating the mixture to produce a reaction product comprising the carbon-coatedmetal-containing compound; wherein during heating step b) the initial average oxidation state of the one or more metalsin the metal precursor compound is reduced; andwherein at least a portion of the carbon coating comprises sp2 carbons.

2. The method according to claim 1, wherein the metal-containing compound has theformula: AaMb(XcYd)eZf wherein: A is an alkali metal selected from one or more of lithium and potassium; M comprises one or more metals selected from transition metals, non-transition metals, and metalloids; (XcYd)eis at least one first anion; and Z is at least one second anion; wherein a ≥0; b >0; c >0; d ≥0; e >0 and f ≥0; wherein a, b, c, d, e and f are chosen to maintain electroneutrality; wherein X comprises one or more elements selected from titanium, vanadium, chromium, arsenic, molybdenum, tungsten, niobium, manganese, aluminium, selenium, boron, oxygen, carbon, silicon, phosphorus, nitrogen, sulfur, fluorine, chlorine, bromine and iodine; and wherein Y is selected from one or more halides, sulfur-containing groups, oxygen- containing groups and mixtures thereof.

3. The method according to any preceding claim, wherein M is a metal selected from oneor more of titanium, vanadium, niobium, tantalum, hafnium, chromium, molybdenum, tungsten, manganese, iron, osmium, cobalt, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, aluminium, scandium, yttrium, zirconium, technetium, rhenium, ruthenium, rhodium, iridium, mercury, gallium, indium, tin, lead, bismuth, magnesium, calcium, beryllium, strontium and barium, boron, silicon, germanium, arsenic, antimony and tellurium.

4. The method according to any preceding claim, wherein Z is selected from one or morehalides, hydroxide-containing groups and mixtures thereof.

5. The method according to any preceding claim, wherein X comprises phosphorus.

6. The method according to any preceding claim, wherein (XcYd)e is a PO4 and / or P2O7moiety.

7. The method according to any preceding claim, wherein the metal-containing compoundis selected from one or more of the group consisting of LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4, LiMn0.5Fe0.2Mg0.3PO4, Li3V2(PO4)3, LiMn0.5Fe0.5PO4, LiVPO4F, Li3V(PO4)2, LiVP2O7, LiVOPO4, LiV2O5, VPO4, MoP2O7, MoOPO4, Fe3(PO4)2, LiFeSO4F, LiMnSO4F, Li2Fe2(SO4)3, Li2Fe(SO4)2, KVPO4F, KVOPO4, K3V2(PO4)3, K3V2(PO4)2F3, KFePO4, and KCoPO4.

8. The method according to any of claims 1 to 6, wherein the metal-containing compoundhas the formula: LiMPO4, where M is a metal selected from one or more of manganese, iron, cobalt, nickel, copper, zinc, magnesium, calcium and combinations thereof.

9. The method according to any of claims 1 to 6, wherein the metal-containing compoundis selected from LiFePO4, LiFe1-xMnxPO4, LiFe1-xMgxPO4and LiFe1-x-yMnxMgyPO4. 10.The method according to any of claims 1 to 6, wherein the metal precursor compound is selected from one or more of Fe2O3, Fe3O4, FeOOH, FePO4.xH2O, FePO4, Fe3(PO4)2, FeSO4.xH2O, Fe(NO3)3, Fe(CH3CO2)2, C6H8O7xFe3+.yNH3(ammonium iron (III) citrate), C6H5FeO7(iron (III) citrate) and Fe(C5H7O2)3(iron (III) 2,4-pentanedionate), wherein x, y are ≥0.11.The method according to any preceding claim, wherein the mixture comprises one ormore compounds selected from LiH2PO4, Li3PO4, LiPO3, Li2CO3, Li2SO4, Lithium citrate,Li2HPO4, LiOH, H3PO4, (NH4)2HPO4 and (NH4)H2PO4, preferably LiH2PO4 or Li2CO3, or ahydrate thereof.12.The method according to any preceding claim, wherein the mixture in a) furthercomprises particulate carbon, and / or one or more carbon-containing polymers. 13.The method of claim 12, wherein the particulate carbon is present in an amount of from 2.5% to 50%, or 5% to 20%, based on the combined weight of pitch and particulate carbon. 14.The method according to any preceding claim, wherein the heating step b) comprises heating at a first temperature sufficient to melt the pitch and heating at a secondtemperature sufficient to convert the pitch to carbon, optionally wherein the firsttemperature is in the range of 50 °C to 250 °C and wherein the second temperature isin the range of 300 °C to 1500 °C.15.The method according to any preceding claim, wherein the pitch is selected from coal tar pitch, bitumen, asphalt, or combinations thereof.16.The method according to claim 14 or 15, wherein at least part of the pitch is convertedto elemental carbon during heating at the second temperature, optionally, wherein atleast part of the pitch is converted to sp2 carbon.17.The method according to any preceding claim, wherein the pitch is selected from coal pitch, petroleum pitch, or a combination thereof.18.The method according to any preceding claim, wherein the pitch is soluble in a solvent,optionally wherein the method comprises mixing the pitch in a solvent, followed byevaporating the solvent prior to or during heating.19.The method according to any preceding claim, further comprising contacting themixture with a reducing gas during heating step b), optionally wherein the reducinggas is selected from CO, H2, and combinations thereof. 20.The method according to any preceding claim, wherein the carbon-coated metal- containing compound has a total carbon content of from 1 to 5% by weight carbon.21.Use of pitch in a carbothermal reduction reaction of a metal precursor compound toproduce a carbon coated metal-containing compound, wherein at least a portion of the carbon coating comprises sp2carbons.22.The use according to claim 21, further comprising using particulate carbon in thecarbothermal reduction reaction.23.An electrode active material made according to the method of any one of claims 1 to20. 24.A composition comprising LiFePO4in particulate form prepared according to the method of any one of claims 1 to 20, wherein the particles are at least partially coated with a carbon coating, and wherein at least a portion of the carbon coating comprises sp2carbons. 25.A battery comprising an electrode comprising a carbon-coated metal-containing compound produced according to the method of any one of claims 1 to 20, optionally wherein the battery is a rechargeable battery, optionally wherein the battery is an alkali metal ion battery, such as a lithium ion battery. 26.Use of a carbon-coated metal-containing compound produced according to the method of any one of claims 1 to 20 as an electrode in a rechargeable battery, optionallywherein the battery is an alkali metal ion battery, optionally wherein the battery is alithium ion battery.

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