Method for producing a metal-carbon composite

Abstract

A method for producing a metal-carbon composite comprising a metal-containing compound and carbon, the method comprising the steps of: a) forming a mixture comprising: i) a carbon source comprising a carbon-containing polymer, pitch, a hydrocarbon, biomass, or combinations thereof; ii) one or more alkali metal precursor compound(s); 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 iv) elemental iron and / or Fe-P waste slag; b) heating the mixture under an inert atmosphere to produce a reaction product comprising the metal-carbon composite; wherein during heating step b) the initial average oxidation state of the one or more metals in the metal precursor compound is reduced; and often wherein the metal-containing compound has the formula: AaMb(XcYd)eZf wherein: A is an alkali metal selected from one or more of lithium, sodium and potassium; M comprises iron and optionally one or more additional metals selected from transition metals, non-transition metals, and metalloids; (XcYd)e is 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. Often wherein at least a portion of the carbon coating comprises sp2 carbons. Also, electrode active material made according to the method; batteries comprising an electrode comprising a metal-carbon composite produced according to the method; the use of a metal-carbon composite produced according to the method as an electrode in a rechargeable battery, the use of a carbon source comprising a carbon- containing polymer, pitch, particulate carbon, a hydrocarbon, or combinations thereof, and elemental iron and / or Fe-P waste slag in a ferrothermal assisted carbothermal reduction reaction of a metal precursor compound to produce a metal-carbon composite; and 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.

Description

[0001] METHOD FOR PRODUCING A METAL-CARBON COMPOSITE

[0002] The present invention relates to methods for producing metal-carbon composites comprising a metal-containing compound and carbon, which can be used as electrode materials for batteries, capacitors, or other energy storage devices.

[0003] Metal-containing compounds, such as alkali metal phosphates, have attracted considerable attention in recent years due to their high capacity, good rate performance, and improved stability as electrode materials for various energy storage devices.

[0004] One well-established approach for synthesising electrode materials is the carbothermal reduction (CTR) process. In this process, a metal precursor compound is heated at an elevated temperature in the presence of an alkali metal precursor compound and an excess of particulate carbon under an inert or reducing atmosphere to form a compound containing a reduced metal or metal alloy (e.g. Fe2+) and carbon monoxide or carbon dioxide as byproducts. The reaction temperature, time, and atmosphere can be adjusted to control the size, morphology, composition, and phase purity of the product.

[0005] 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, and US10050271B2, which is also incorporated herein by reference, and which describes methods for performing carbothermal reduction of metal precursor compounds in the presence of elemental phosphorus.

[0006] The conventional carbothermal reduction processes used for the production of high-quality electroactive materials face several significant challenges. Primarily, the high cost of metal precursors is a considerable economic burden. Additionally, the high temperatures necessary for these reactions, typically exceeding 1000°C, result in substantial energy consumption, further increasing operational costs.

[0007] Given these challenges, there is a pressing need for more cost-effective and environmentally sustainable processes for the production of high-quality electroactive materials, which can be easily scaled up using industry standard equipment. There is also a need for processes that operate at lower temperatures while still yielding high-purity, high-performance electrode active materials.Accordingly, in a first aspect of the invention, there is provided a method for producing a metal-carbon composite comprising a metal-containing compound and carbon, the method comprising the steps of:

[0008] a) forming a mixture comprising:

[0009] i) a carbon source comprising a carbon-containing polymer, pitch, particulate carbon, a hydrocarbon, biomass, or combinations thereof;

[0010] ii) one or more alkali metal precursor compound(s);

[0011] 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 iv) elemental iron and / or Fe-P waste slag;

[0012] b) heating the mixture under an inert atmosphere to produce a reaction product comprising the metal-carbon composite;

[0013] wherein during heating step b) the initial average oxidation state of the one or more metals in the metal precursor compound is reduced.

[0014] The present invention provides a new, scalable method for producing a metal-carbon composite comprising a metal-containing compound and carbon, which can be used as an electrode material for various types of batteries, such as alkali metal-ion batteries (e.g. lithium-ion batteries and sodium-ion batteries). In the method according to the first aspect of the invention, the carbon source defined herein (i.e. component (i)), alkali metal precursor compound defined herein (i.e. component (ii)), metal precursor compound defined herein (i.e. component (iii)), and elemental iron and / or Fe-P waste slag (i.e. component (iv)) react to form particles of a carbon-containing alkali metal-metal composite product. Without being bound by theory, during heating, the precursor materials predominantly react with the elemental iron and / or Fe-P waste slag to form a reduced metal-containing compound, without full reduction of the metal in the metal precursor to an elemental state. The presence of carbon from the carbon-source within the composite enhances the electronic conductivity of the material and may also react with the precursor materials and assist in the formation of a reduced metalcontaining compound.

[0015] As used herein, the term “metal-carbon composite” refers to a composite material comprising carbon and a metal-containing compound as described herein. The carbon source can be integrated within the metal-containing compound. For instance, forming an electrically conductive carbon matrix between the metal-containing particles. Additionally, or alternatively, the carbon source can form an external coating on a surface of particles of the metalcontaining compound or agglomerates formed from two or more particles of the metal-containing compound. The presence of carbon within the metal-carbon composite (i.e. integrated within the metal-containing compound and / or forming an external coating) provides composite materials with high electronic conductivity, which has advantageous properties when used to form an electrode, such as a cathode, of a battery, capacitor, or other energy storage device.

[0016] As used herein, the term “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.

[0017] The carbon source comprises one or more of a carbon-containing polymer, pitch, particulate carbon, a hydrocarbon, biomass, or combinations thereof. Alternatively, the carbon source may comprise one or more of a carbon-containing polymer, pitch, particulate carbon, a hydrocarbon, or combinations thereof.

[0018] Use of a carbon source as defined herein enhances the electronic conductivity of the resultant composite. Carbon sources produced from carbohydrates, such as monosaccharides (e.g. glucose) and disaccharides (e.g. sucrose) have been studied previously in the art. However, these sources have relatively low conductivity, resulting in composite materials having poor suitability for use in electrode active materials. As such, metal-carbon composites generated using the method according to a first aspect of the invention have a high electronic conductivity and are suitable for use as electrode active materials with superior properties to composite materials using mono- and disaccharides.

[0019] The quantity of the carbon source used in the method may be sufficient to provide a stoichiometric molar excess of carbon with respect to the metal precursor compound. This is so that sufficient carbon is present to enhance the resultant electronic conductivity. The molar equivalents of carbon can be calculated based on the weight per gram-mole of carbon atoms. Further, it has been found that where the molar excess of carbon is in the range 0 - 100% assuming a carbon monoxide carbothermal reduction mechanism (equating to 0 - 3.5 wt% carbon excess (Cexcesswt%)), a good density and high discharge capacity are observed.

[0020] For particulate carbons such as carbon black, graphite, and so on, the equivalent weight can be about 12 g / equivalent, whereas for carbon-containing polymers, the equivalent weight per gram-mole of carbon atoms is higher. For example, polymers containing predominantly or entirely carbon and hydrogen in the polymer chain have an equivalent weight of about 14 g / equivalent. Depending on the degree of unsaturation and non-carbon atoms, the equivalent weight of the carbon-containing polymer may be slightly above or below 14. When pitch isused in the method, the quantity may be sufficient to provide a stoichiometric molar excess of carbon with respect to the metal precursor compound. This is so that sufficient carbon is present to contribute to the overall reduction of the metal precursor compound and ensure that carbon is present in the resultant composite material produced. The molar equivalents of carbon can be calculated based on the weight per gram-mole of carbon atoms.

[0021] It may be the case that the carbon source comprises a carbon-containing polymer, pitch, a hydrocarbon, biomass, or combinations thereof. In the event that the carbon source comprises a carbon-containing polymer, pitch, a hydrocarbon, or combinations thereof, it may be the case that the metal-carbon composite formed is a carbon-coated metal-containing compound. In other words, the metal-carbon composite is in the form of a carbon-coated metal-containing compound.

[0022] According to a second aspect of the invention, there is provided a method for producing a metal-carbon composite comprising a carbon-coated metal-containing compound, the method comprising the steps of:

[0023] a) forming a mixture comprising:

[0024] i) a carbon source comprising a carbon-containing polymer, pitch, a hydrocarbon, biomass, or combinations thereof;

[0025] ii) one or more alkali metal precursor compound(s);

[0026] 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 iv) elemental iron and / or Fe-P waste slag;

[0027] b) heating the mixture under an inert atmosphere to produce a reaction product comprising the carbon-coated metal-containing compound;

[0028] wherein during heating step b) the initial average oxidation state of the one or more metals in the metal precursor compound is reduced. It may be the case that at least a portion of the carbon coating comprises sp2carbons.

[0029] In the method according to the second aspect of the invention, the carbon source comprising a carbon-containing polymer, pitch, a hydrocarbon, biomass, or combinations thereof (i.e. component (i)), alkali metal precursor compound defined herein (i.e. component (ii)), metal precursor compound defined herein (i.e. component (iii)), and elemental iron and / or Fe-P waste slag (i.e. component (iv)) react to form particles of a carbon-containing alkali metalmetal composite product. Without being bound by theory, during heating, the precursor materials react with the elemental iron and / or Fe-P waste slag to form a reduced metal-containing compound, without full reduction of the metal in the metal precursor to an elemental state and the carbon source is decomposed in an inert atmosphere (pyrolyzed) and may form a carbon coating on the particles. It may be the case that some of the carbon source may also form an electrically conductive carbon matrix between the carbon-coated metal particles, resulting in a highly electrically conductive composite material which has advantageous properties when used to form an electrode, such as a cathode, of a battery, capacitor, or other energy storage device. The carbon source may also react with the precursor materials and assist in the formation of a reduced metal-containing compound.

[0030] As used herein, the term “carbon-coated” will be understood to refer to a layer of carbon deposited on the surface of the particles of the metal-containing compound or agglomerates formed from two or more particles of the metal-containing compound. It may be the case that at least 50% of the surface of the particles of the metal-containing compound or agglomerates formed from two or more particles of the metal-containing compound is covered. It may be the case that at least 70% of the surface of the particles of the metal-containing compound or agglomerates formed from two or more particles of the metal-containing compound is covered. It may be the case that at least 80% of the surface of the particles of the metal-containing compound or agglomerates formed from two or more particles of the metal-containing compound is covered. It may be the case that at least 90% of the surface of the particles of the metal-containing compound or agglomerates formed from two or more particles of the metal-containing compound is covered. It may be the case that at least 99% of the surface of the particles of the metal-containing compound or agglomerates formed from two or more particles of the metal-containing compound is covered. The percentage surface coverage of the particles of the metal-containing compound or agglomerates formed from two or more particles of the metal-containing compound can be determined using any known technique. Examples of techniques include, but are not limited to, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM).

[0031] It may be the case that the carbon-coated metal-containing compound comprises a carbon coating, wherein at least a portion of the carbon coating comprises sp2carbons. As used herein, the term “sp2carbon” may also be referred to as “sp2graphitic carbon” or “networked sp2hybridised carbon", and refers to the situation where a carbon atom forms three sigma (o) bonds with other carbon atoms in the plane, creating a hexagonal lattice, and a pi (TT) bond above and below the plane, which provides delocalised electrons that contribute to the electrical conductivity and stability of the carbon-coated metal-containing compound. In other words, the carbon atoms are in a sp2hybridised state, similar to those found in graphite and include regions of honeycomb arrangements of sp2carbon atoms.It may be the case that at least 5% of the carbon atoms in the carbon coating may be sp2hybridised carbon, often at least 10%, often at least 20%, often at least 30%, often at least 40%, often at least 50%, often at least 60%, often at least 70%, often at least 80%, often at least 90%, more often at least 95%. It may be the case that the percentage of carbon atoms in the carbon coating are sp2hybridised in a range between any two of the aforementioned percentage values. The presence of sp2hybridised carbon atoms in the coating at these levels ensures high conductivity while minimising the amount of carbon needed.

[0032] The thickness of the carbon coating on a particle of the metal-containing compound or an agglomerate formed from two or more particles of the metal-containing compound may be less than 100 nm. It may be the case that the thickness of the carbon coating is less than 75 nm. It may be the case that the thickness of the carbon coating is less than 50 nm. It may be the case that the thickness of the carbon coating is less than 20 nm. It may be the case that the thickness of the carbon coating is less than 10 nm. It may be the case that the thickness of the carbon coating is in the range 1 nm to 20 nm, often in the range 1 nm to 15 nm, often in the range 1 nm to 10 nm, often in the range 1 nm to 8 nm, often in the range 1 nm to 5 nm. Measurement of the thickness can be performed by any known technique. Examples of techniques that can be used include, but are not limited to, Scanning Electron Microscopy (SEM) by visual analysis of a SEM image, Transmission Electron Microscopy (TEM) by visual analysis of a TEM image, and Atomic Force Microscopy (AFM). Often, the thickness of the coating is measured by Transmission Electron Microscopy (TEM).

[0033] The carbon source may comprise a carbon-containing polymer. As used herein, the term “carbon-containing polymer” takes its usual meaning in the art and refers to a polymer that includes carbon atoms in its molecular structure. It has been discovered that carbon-containing polymers are especially useful as the carbon source for the method according to the first aspect and second aspect of the invention. During the heating step, the carbon-containing polymer may initially flow (when the temperature of the step is preferably above or close to its melt temperature) and can coat the metal precursor particles and is then decomposed in situ to elemental carbon. It may be the case that the carbon-containing polymer also produces reducing gases (such as CH4, H2and combinations thereof) during decomposition. The reducing gases may contribute to the reduction of the metal in the metal precursor compounds (for example, reducing Fe3+to Fe2+). During the heating step of the method according to the first aspect and second aspect of the invention, the carbon-containing polymer may form a carbon coating on the surface of the metal-containing compound, which can improve the conductivity, stability, and performance of the material when used as anelectrode material. Advantageously, the carbon-containing polymer also assists in compaction / pelletisation of the mixture prior to heating by acting as a binder. This enhanced compaction minimises gaps between the reactant particles, aids the kinetics of the solid-state carbothermal reaction that takes place, and generally improves product formation. Finally, carbon-containing polymers are also relatively low cost in comparison to other carbon sources, which will lower the overall cost expenditure.

[0034] When the carbon source comprises a carbon-containing polymer, it may be the case that at least part of the carbon-containing polymer may be converted to sp2hybridized carbon. Conversion of the carbon-containing polymer to sp2carbon may result in graphitisation of the carbon, particularly in the presence of iron (for instance, elemental iron present in component (iv) described herein, or wherein the metal precursor (i.e. component (iii)) comprises iron). This enhances the electrical conductivity. Iron compounds advantageously catalyse the graphitisation process at relatively low reaction temperatures.

[0035] The carbon-containing polymer used in the method according to the first and the second aspects of the invention can be any polymer that contains carbon atoms in its backbone or side chains and that can decompose under heat to form carbon and volatile products. The carbon-containing polymer may be selected from the group consisting of polyethylene (PE), high modulus polyethylene (HMPE), high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), high modulus polypropylene (HMPP), high density polypropylene (HDPP), low density polypropylene (LDPP), 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 (PCs), polyamides (such as nylon), or a combination thereof. It may be the case that the carbon-containing polymer is selected from the group high modulus polyethylene (HMPE), high density polyethylene (HDPE), low density polyethylene (LDPE), high density polypropylene (HDPP), low density polypropylene (LDPP), polyethylene terephthalate (PET), or a combination thereof.

[0036] Preferably, the carbon-containing polymer has a high carbon content. It may be the case that the carbon-containing polymer is selected from polyethylene, polypropylene, high modulus polyethylene, and high modulus polypropylene.

[0037] It may be the case that the carbon-containing polymer comprises an elastomer. As used herein, the term “elastomer” takes its usual meaning in the art and refers to a polymer thatexhibits elastic properties and can be stretched or deformed and return to its original shape. Examples of elastomers include, but are not limited to, natural rubber, synthetic rubber, silicone, and polyurethane. An advantage of using an elastomer as the carbon-containing polymer is that it can form a conformal and uniform coating on the metal precursor particles due to its flexibility and viscosity. Moreover, an elastomer can decompose under heat to form carbon and volatile products that can assist in the reduction of the metal precursor compounds. The elastomer may comprise rubber, which is a natural or synthetic material that contains polymers of isoprene or other dienes. Rubber can pose a significant environmental problem due to its non-biodegradability and accumulation in landfills. Therefore, using rubber as the carbon-containing polymer can provide a beneficial way of recycling and reusing waste rubber materials, such as discarded tyres, and converting them into valuable electrode materials. The rubber can be tyre rubber, which is a type of rubber that is used for making tyres for vehicles. Tyre rubber typically comprises natural or synthetic rubber, carbon black, sulphur, and other additives. By containing a combination of elastomer and carbon black, tyre rubber provides a useful input material as it contains both a meltable polymer and particulate carbon. The tyre rubber can be de-vulcanized prior to or during the heating process. As used herein, the term “vulcanization” takes its usual meaning in the art and refers to a chemical process that involves cross-linking the rubber molecules with sulphur or other agents to improve the strength and durability of the rubber. De-vulcanization is a process that reverses vulcanization and breaks the cross-links between the rubber molecules, resulting in a softer and more flexible rubber product. De-vulcanization can be achieved by various known methods, such as thermal, mechanical, chemical, or biological methods, or any combination thereof. By using de-vulcanized tyre rubber as the carbon-containing polymer, the method of the invention can reduce the amount of sulphur and other impurities in the final product and thereby enhance its electrical performance. It may be the case that the carbon-containing polymer comprises an elastomer obtained from rubber.

[0038] The carbon-containing polymer may comprise a halogen selected from Cl, Br, F, or I. The carbon-containing polymer comprising a halogen can be any polymer that contains one or more of Cl, Br, F, or I atoms in its backbone or side chains. Examples of halogenated carbon-containing polymers include, but are not limited to, polyvinylchloride (PVC), polyvinylidene fluoride (PVdF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), poly(chlorotrifluoroethylene) (PCTFE), poly(tetrafluoroethylene) (PTFE), poly(vinyl fluoride) (PVF), poly(vinylidene chloride) (PVDC), poly(vinyl bromide) (PVB), poly(vinylidene bromide) (PVDB), poly(ethylene-co-tetrafluoroethylene) (ETFE), poly(fluoroethylene propylene) (FEP), poly(ethylene chlorotrifluoroethylene) (ECTFE), poly(tetrafluoroethylene-co-perfluoromethyl vinyl ether) (MFA), poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA),polyperfluoroalkoxy alkanes (PFAAs), perfluoropolyether (PFPE), polyhexafluoropropylene (PHFP), polytrifluorochloroethylene (PTFCE), polyvinylidene fluoride-co-trifluoroethylene (PVDF-TrFE), polychloroprene, polybromostyrene, poly(fluoroalkyl acrylate), poly(fluoroalkyl methacrylate), poly(chloroalkyl acrylate), poly(chloroalkyl methacrylate), poly(bromoalkyl acrylate), poly(bromoalkyl methacrylate), or any combination thereof.

[0039] The halogenated carbon-containing polymer may be selected from polyvinylidene fluoride (PVdF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), poly(chlorotrifluoroethylene) (PCTFE), poly(tetrafluoroethylene) (PTFE), polyvinylchloride (PVC), or a combination thereof. The halogenated carbon-containing polymer may be selected from polyvinylidene fluoride (PVdF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), polyvinylchloride (PVC), or a combination thereof.

[0040] The halogen may dope the metal-carbon composite and thereby enhance its electrical performance. A carbon-containing polymer comprising a halogen selected from Cl, Br, F, or I can provide additional benefits for the method of the invention. For example, the halogen atoms can be incorporated into the metal-containing compound as dopants or intercalants, which can modify the electrochemical properties of the metal-containing compound and improve its performance as an electrode material. For example, fluorine or chlorine doping or intercalation can increase the specific capacity, rate capability, and cycling stability of metal precursor materials. Additionally, the halogen atoms can react with other elements in the metal precursor compound or the carbon-containing polymer to form volatile compounds, such as hydrogen halides or carbon halides, that can be removed from the system during the heating process. This can reduce the amount of impurities and byproducts in the final product.

[0041] The carbon-containing polymer can be used in any form, such as particulate form (i.e. a powder or a granule), pellet form, a film, a fiber, a fabric, or a foam. For example, the carbon-containing polymer can be prepared by cryomilling. It may be the case that the carbon-containing polymer is in particulate form. It may be the case that the average particle size (i.e. the number average diameter) of the carbon-containing polymer is less than 20 µm. It may be the case that the average particle size (i.e. the number average diameter) of the carbon-containing polymer is in the range 1 µm to 20 µm, often 1 µm to 10 µm, often 1 µm to 5 µm. The average particle size (i.e. the number average diameter) can be determined using any known technique. Examples of techniques used to determine average particle size include, but are not limited to, Laser Diffraction, Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM), and Sieve Analysis.The carbon-containing polymer(s) can be derived from various sources, such as virgin polymer materials, recycled polymer materials, waste polymer materials, or biomass-derived polymer materials. It may be the case that the carbon-containing polymer(s) is derived from waste polymer materials, such as plastic waste (e.g. waste PET, PS, PE, PP etc collected from waste products), packaging waste, textile waste, or tyre waste, which can reduce the cost and environmental impact of the method of the invention.

[0042] The carbon-containing polymer may be soluble in a polar solvent. Optionally, the solvent may be acetone or water (or another polar solvent). Optionally, the method may comprise mixing the carbon-containing polymer in the solvent and evaporating the solvent prior to or during heating. The solvent may improve mixing of the precursors and the carbon-containing polymer. The method can include a step of dissolving the carbon-containing polymer in a polar solvent to facilitate the dispersion and mixing of the carbon-containing polymer with the metal precursor particles. The solvent can be evaporated prior to or during the heating process, leaving behind a heterogeneous mixture of the carbon-containing polymer and the metal precursor particles. The evaporation of the solvent can also generate gas that can assist in the reduction of the metal precursor compounds and contribute to the formation of a carbon coating. The use of a polar solvent can improve the quality and uniformity of the electrode material produced by the method of the invention. Including a step of dissolving the carbon-containing polymer in a polar solvent may result in a metal-carbon composite which, when used as an electrode material, produces a higher specific capacitance and lower resistance than electrode materials prepared without the dissolution step.

[0043] It may be the case that the carbon-containing polymer may be replaced or supplemented in the mixture by phytic acid (CeHisC^Pe, also referred to as inositol hexaphosphate, inositol hexakisphosphate (IP6) or inositol polyphosphate), which may act as both a phosphorus and carbon source. The phytic acid may be pyrolyzed to form a carbon coating on the particles and agglomerates of the metal compound in the same manner as the polymer.

[0044] As used herein, the term “pitch” takes its usual meaning in the art and refers to highly viscous liquids, which may in some cases appear solid, obtained from petroleum, coal or plant sources. Pitch is a viscoelastic polymer.

[0045] The carbon source may comprise pitch. In the event that the carbon source comprises pitch, it can be derived from any suitable source (including petroleum, coal and plant matter), provided that it can decompose under heat to 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. Pitch sourced from petroleum 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 sourced from petroleum or coal may be characterised as including at least two of the above-listed PAHs, but preferably at least 3, 4, 5, 67, 8, 9, 10, 11, 12, 13, 14, 15, or all, of the above-listed PAHs.

[0046] As used herein, the term “asphalt” refers to a sticky, black and highly viscous liquid or semi solid that is present in crude oil and in some natural deposits sometimes termed asphaltum. Asphalt is a type of pitch derived from crude petroleum. Asphalt contains, among other hydrocarbon components, asphaltenes, which have a C: H ratio of approximately 1:1.2 and a distribution of molecular masses in the range of 400 u to 1500 u. As used herein, the term “bitumen” refers to a sticky, black, and highly viscous liquid or semi-solid form of petroleum, which is a component of asphalt. In US terminology, asphalt (or asphalt cement) is the carefully refined residue from the distillation process of selected crude oils. Outside of the US, asphalt and bitumen are sometimes used interchangeably; however, as noted above, bitumen is a component of asphalt. Asphalt comprises other aggregate materials (e.g. sand or gravel) in addition to bitumen.

[0047] As used herein, the term “tar” refers to a black thermoplastic type of pitch produced by the destructive distillation of coal - sometimes referred to as coal tar, or coal tar pitch. Tar is also a residue in the manufacture of coal gas and coke. It may also be derived from plants such as pine trees.

[0048] It may be the case that the carbon source comprises pitch selected from coal tar pitch, asphalt, bitumen, or combinations thereof. It may be the case that the pitch is selected from coal tar pitch.

[0049] Where the carbon source is derived from biomass, this may be unprocessed biomass, processed biomass, or a combination thereof. As used herein, the term “unprocessed biomass" takes its usual meaning in the art and refers to raw biological material derived from plant or organic sources that has not undergone any chemical, thermal, or mechanical transformation beyond basic physical preparation (e.g., drying, grinding, or sieving). Examples include, but are not limited to, untreated nut shells, sawdust, rice husks, straw, and coffee grounds. The term “processed biomass" takes its usual meaning in the art and refers tobiomass that has been subjected to one or more chemical, thermal, or mechanical treatments to alter its composition, structure, or physical state. This includes, for example, materials such as bio-oil obtained via pyrolysis, liquefaction, or alcoholysis; fractions derived from bio-oil; and chemically modified biomass derivatives such as polymerised derivatives. Carbon sources derived from biomass, in both processed and unprocessed forms, offer distinct advantages when applied in carbothermal reduction and ferrothermal-assisted carbothermal reduction processes. These materials typically contain significantly lower levels of sulphur and other heteroatoms compared to petrochemical-derived carbons, thereby reducing the risk of impurity incorporation into the final product. Furthermore, carbon derived from biomass exhibits physical and chemical characteristics that can improve carbon-metal interactions, enhance dispersion, and contribute to the formation of a more uniform and conductive matrix. These properties result in composites with improved purity, and which exhibit suitable conductivity and electrochemical stability.

[0050] It may be the case that the one or more materials derived from biomass are selected from biooil, at least one fraction derived from bio-oil, agricultural waste or forestry waste, or a combination thereof.

[0051] As used herein, the term “bio-oil” refers to any liquid derived from biomass, including but not limited to thermochemical conversion products (such as pyrolysis oil, liquefaction oil, alcoholysis oil, or acidolysis oil), as well as naturally occurring or extracted bio-based liquids such as vegetable oil, glycerol, or nut shell-derived oils. Bio-oils that are thermochemical conversion products typically comprise a mixture of oxygenated organic compounds, including phenolics, aldehydes, ketones, acids, and hydrocarbons, and may vary in composition depending on the biomass feedstock and processing conditions.

[0052] As used herein, the term “bio-based liquid” refers to any liquid material derived wholly or predominantly from renewable biological sources, including but not limited to plant, algal, or microbial biomass. Bio-based liquids may be obtained from renewable biological sources by direct extraction, mechanical processing, chemical conversion, or fermentation.

[0053] Examples of bio-oil include, but are not limited to bio-based liquids such as vegetable oils (such as soybean oil, canola oil, sunflower oil, palm oil, and corn oil), glycerol (a polyol byproduct of biodiesel production or fat hydrolysis), plant-derived oils and extracts (such as cashew nut shell liquid, tall oil, or citrus oils), fermentation-derived liquids such as bio-based alcohols or organic acids; and bio-oils produced by the thermochemical conversion of biomass(including wood oil, straw-derived bio-oil, and nut shell-derived oil). These bio-oils may be used as received or subjected to further purification, fractionation, or chemical modification.

[0054] As used herein, the term “fractions derived from bio-oil” refers to components or sub-products obtained from bio-oil through physical or chemical separation techniques, such as distillation, solvent extraction, phase separation, or chemical modification. These fractions may include, but are not limited to, bioasphaltene, biomaltene, bio-bitumen, a bio-binder, heavy bio-oil fractions, hydrothermal liquefaction residues, lignin-rich pyrolysis products, and pitch-like biomass derivatives.

[0055] As used herein, the term “agricultural and forestry waste” refers to biomass residues generated from agricultural and forestry activities that are not primarily intended for food, fuel, or timber production. These materials are typically by-products or discarded components of crop cultivation, harvesting, or wood processing. Agricultural waste may include, but is not limited to, nut shells, coffee grounds, rice husks, rice straw, corn stover, furfural residues, and other plant-derived residues. Forestry waste may include sawdust, bark, wood chips, lignin, and other non-commercial wood fractions. Such materials may be used in unprocessed or processed form and are valued for their carbon content and availability.

[0056] It may be the case that the one or more materials derived from biomass comprise agricultural waste or forestry waste. The agricultural or forestry waste may be selected from nut shells (such as cashew nut shells, pistachio nut shells, walnut shells, almond nut shells, Brazil nut shells, or combinations thereof), coffee grounds, sawdust, lignin, biochar, humins, tannin-based compounds, rice husks, rice straw, corn stover, furfural residues, or a combination thereof. The agricultural or forestry waste may be selected from cashew nut shells, pistachio nut shells, coffee grounds, sawdust, or a combination thereof. The agricultural or forestry waste may be selected from cashew nut shells, sawdust, or a combination thereof.

[0057] It may be the case that the one or more materials derived from biomass comprise a bio-oil. It may be the case that the bio-oil is obtained from biomass through pyrolysis, alcoholysis, acidolysis, or liquefaction. As used herein, the term “pyrolysis” takes its usual meaning in the art, and involves the thermal decomposition of biomass in the absence of oxygen, typically at temperatures between 400 °C and 600 °C. This process typically yields a liquid bio-oil phase, along with solid char and gaseous products. The composition of the resulting bio-oil depends on the feedstock and process parameters, and typically includes phenolics, aldehydes, ketones, acids, and other volatile organics. As used herein, the term “alcoholysis” takes its usual meaning in the art, and refers to a solvolysis process in which biomass is reacted withan alcohol (e.g., methanol or ethanol) under elevated temperature and pressure, often in the presence of a catalyst. This process breaks down lignocellulosic structures and produces a bio-oil rich in alkylated phenolic and ester compounds. As used herein, the term “acidolysis” takes its usual meaning in the art, and involves the depolymerisation of biomass using an acid catalyst, typically under mild to moderate thermal conditions. This method can selectively cleave ether and ester linkages in lignin and hemicellulose, typically yielding a biooil phase enriched in aromatic and furanic compounds. As used herein, the term “liquefaction” takes its usual meaning in the art, and refers to the conversion of biomass into a liquid phase using heat and pressure, often in the presence of a solvent and / or catalyst. Hydrothermal liquefaction, for example, uses water at subcritical or supercritical conditions to convert wet biomass into bio-crude, which can be further refined into bio-oil. The resulting biooil may be used directly or subjected to further processing (e.g., distillation, extraction, or chemical modification) to isolate specific fractions or improve stability and performance. It may be the case that the bio-oil is obtained or extracted from a bio-based liquid.

[0058] It may be the case that the bio-oil is selected from wood oil, straw-derived bio-oil, bagasse-derived bio-oil, peat-derived bio-oil, nut shell-derived oil, glycerol, a vegetable oil, or a combination thereof. The nut shell-derived oil may be selected from cashew nut shell-derived oil, pistachio nut shell-derived oil, walnut shell-derived oil, almond shell-derived oil, or a combination thereof. It may be the case that the cashew nut shell-derived oil is selected from cashew nut shell liquid (CNSL) or a derivative thereof, polymerized cashew nut shell liquid (CNSL), refluxed cashew nut shell liquid (CNSL), or a combination thereof. As used herein, “cashew nut shell liquid” (CNSL) refers to a non-edible, phenolic-rich oil obtained as a byproduct from the processing of cashew nuts.

[0059] As is understood in the art, CNSL is a complex mixture primarily comprising anacardic acid, cardanol, cardol, and 2-methylcardol, with the precise composition depending on the extraction and processing method employed (e.g., hot oil bath, solvent extraction, roasting, or pyrolysis). CNSL may be used in its raw or technical grade, or may be subjected to further chemical or thermal modification, such as polymerisation, refluxing, or fractionation, to tailor its viscosity, reactivity, or carbon yield. Owing to its high carbon content, aromatic structure, and natural abundance, CNSL provides a sustainable, renewable, and cost-effective alternative to petroleum-derived carbon sources. The use of CNSL as a carbon precursor is further advantageous in that it is compatible with scalable manufacturing processes. Cashew nut shell liquid (CNSL) is an advantageous carbon source for the preparation of electrode materials due to its renewable and high availability as a byproduct of the cashew industry. It is rich in phenolic compounds with aromatic structures, enabling efficient carbonisation andthe formation of conductive, graphitic carbon. CNSL’s chemical properties can be tailored through various modifications, allowing for the production of carbon materials with optimized conductivity and morphology. For instance, through polymerisation or reflux.

[0060] It may be the case that the one or more materials derived from biomass comprise at least one fraction derived from bio-oil, optionally wherein the at least one fraction derived from bio-oil is selected from bioasphaltene, biomaltene, a bio-binder, bio-bitumen, heavy bio-oil fractions, hydrothermal liquefaction residues, lignin-rich pyrolysis products, pitch-like biomass derivatives, or a combination thereof. It may be the case that the at least one fraction derived from bio-oil comprises bioasphaltene, biomaltene, or a combination thereof.

[0061] As used herein, the terms “bioasphaltene’’ and “biomaltene" refer to distinct fractions derived from bio-oil, typically obtained through solvent separation based on solubility characteristics. Bioasphaltene is defined as the fraction of bio-oil that is insoluble in light aliphatic solvents such as n-heptane or hexane, whereas biomaltene is the soluble fraction in those same solvents. These fractions are analogous to petroleum-derived asphaltenes and maltenes but are produced from renewable biomass sources. Bioasphaltene generally comprises high molecular weight, aromatic-rich compounds with low volatility and high carbon content, making it suitable for use as a carbon source, binder, or structural additive in thermal processing applications. Biomaltene typically contains lower molecular weight compounds, including oxygenated aromatics, phenolics, and aliphatics, and may contribute to flowability, dispersion, and carbon matrix formation. These fractions can be obtained from bio-oil produced via pyrolysis, liquefaction, or other thermochemical conversion processes applied to biomass such as wood, straw, nut shells, or agricultural residues. The bioasphaltene and / or biomaltene may be derived from nut shell-derived oil. The bioasphaltene and / or biomaltene may be derived from cashew nut shell-derived oil. The bioasphaltene and / or biomaltene may be derived from cashew nut shell liquid (CNSL).

[0062] Separation is typically achieved by dissolving the bio-oil in a non-polar solvent, precipitating the bioasphaltene, and recovering the biomaltene from the filtrate. Both fractions may be used individually or in combination, depending on the desired thermal behaviour, carbon yield, and functional properties in the target application.

[0063] Use of a bio-binder is advantageous as it can also assist in compaction / pelletisation of the mixture prior to heating by acting as a binder. This enhanced compaction minimises gaps between the reactant particles, aids the kinetics of the carbothermal reaction according to the first aspect of the invention and the ferrothermal assisted carbothermal reaction according tothe second aspect of the invention, and generally improves product formation. It may be the case that the bio-binder is obtained from bio-oil or a fraction thereof through one or more of distillation, extraction oxidation, or polymer modification.

[0064] As used herein, the term “bio-bitumen" refers to a carbon-rich, viscous material derived from biomass, which serves as a renewable alternative to petroleum-based bitumen. Bio-bitumen may be produced from bio-oil obtained via the thermochemical conversion of biomass, and can comprise bioasphaltene, biomaltene, and other heavy fractions or residues. Bio-bitumen typically exhibits high carbon content, adhesive properties, and thermal stability. It may be the case that the bio-bitumen is obtained from bio-oil or a fraction thereof through one or more of distillation, extraction oxidation, or polymer modification.

[0065] It may be the case that the carbon source comprises bioasphaltene, biomaltene, cashew nut shell liquid (CNSL), sawdust, pistachio shells, wood-oil, glycerol, vegetable oil, or a combination thereof. It may be the case that the carbon source comprises bioasphaltene, biomaltene, cashew nut shell liquid (CNSL), sawdust, or a combination thereof. It may be the case that the carbon source comprises bioasphaltene, biomaltene, or a combination thereof. These carbon sources, especially bioasphaltene and biomaltene, offer safer material handling, and fewer impurities in the resulting composites compared to petroleum-based sources.

[0066] It may be the case that the carbon source comprises one or more materials derived from biomass which are either a liquid at room temperature; soften or melt when subjected to heating step b) under an inert, reducing or low partial pressure atmosphere, optionally at a temperature in the range 50 °C to 1500 °C, often in the range 50 °C to 250 °C; or decompose when subjected to heating step b) under an inert, reducing or low partial pressure atmosphere, optionally at a temperature in the range 50 °C to 1500 °C, often in the range 50 °C to 250 °C, to form a flowable pyrolysis product(s). Such materials can facilitate the formation of at least a partial carbonaceous layer (also referred to as a carbon coating) on the surface of metalcontaining particles during heating step b) of the method according to the first and second aspects of the invention. This behaviour enables more uniform distribution of carbon, improved contact between carbon and active material, and enhanced electrical conductivity in the resulting composite. Additionally, the flowable nature of these materials during heating may promote better surface encapsulation, contributing to improved structural integrity and electrochemical performance of the final product.

[0067] Examples of materials derived from biomass which are either a liquid at room temperature; soften or melt when subjected to heating step b) under an inert, reducing or low partialpressure atmosphere, optionally at a temperature in the range 50 °C to 1500 °C, often in the range 50 °C to 250 °C; or decompose when subjected to heating step b) under an inert, reducing or low partial pressure atmosphere, optionally at a temperature in the range 50 °C to 1500 °C, often in the range 50 °C to 250 °C, to form a flowable pyrolysis product(s) include, but are not limited to one or more of bio-oil, optionally selected from wood oil, straw-derived bio-oil, nut shell-derived oil, glycerol, vegetable oil or a combination thereof; at least one fraction derived from bio-oil, optionally selected from bioasphaltene, biomaltene, bio-bitumen, or a combination thereof; and agricultural waste or forestry waste, optionally selected from cashew nut shells, pistachio nut shells, coffee grounds, sawdust, or a combination thereof.

[0068] During the heating stage of the method according to the first aspect and second aspect of the invention, the pitch may be decomposed in an inert atmosphere (pyrolyzed) to form a carbon coating on the particles. Some of the pitch may also form an electrically conductive carbon matrix between the carbon-coated metal particles, resulting in a highly electrically conductive composite material which has advantageous properties when used to form an electrode, such as a cathode of a battery, capacitor, or other energy storage device. Additionally, pitch has a high percentage carbon content and therefore also has a high carbon to oxygen ratio. This produces a high carbon content coating during pyrolysis. The high C to O ratio also results in the formation of graphitic sp2carbon during pyrolysis, particularly in the presence of iron (for instance, elemental iron present in component (iv) described herein, or wherein the metal precursor (i.e. component (iii) comprises iron)). Iron compounds advantageously catalyse the graphitisation process at relatively low reaction temperatures. Furthermore, pitch (including coal tar pitch, bitumen, asphalt etc.) can help in the precursor compaction process prior to heating and can assist in the reduction of other transition metals e.g. Mn3+.

[0069] 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 dispersion and mixing of the pitch with the metal precursor particles. The solvent can be evaporated prior to or during the heating process, leaving behind a uniform heterogeneous mixture of the pitch and the metal precursor particles. The evaporation of the solvent can also generate gas that can assist in the reduction of the metal precursor compounds and contribute to the formation of a carbon coating. The use of a solvent can improve the quality and uniformity of the electrode material produced by the method of the invention. Including a step of dissolving thepitch in a solvent can result in a metal-carbon composite, which, when used as an electrode material, produces a higher specific capacitance and lower resistance than an electrode material prepared without the dissolution step.

[0070] The carbon source may comprise a hydrocarbon. As used herein, the term “hydrocarbon” takes its usual meaning in the art and relates to compounds that consist solely of hydrogen and carbon atoms. It may be the case that the hydrocarbon is selected from methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), ethene (C2H4), propene (C3H6), butene (C4H8), benzene, or a combination thereof. It may be the case that the hydrocarbon is selected from methane (CH4), ethane (C2H6), propane (C3H8), or a combination thereof. Preferably, the hydrocarbon is methane. It may be the case that the hydrocarbon is a gas at room temperature.

[0071] According to the method of the first aspect of the invention, it may be the case that the carbon source comprises particulate carbon. According to the method of the second aspect of the invention, it may be the case that the carbon source further comprises particulate carbon. Without being bound by theory, particulate carbon can form an electrically conductive carbon matrix between the metal particles of the metal-containing compound, resulting in a highly electrically conductive composite material which has advantageous properties when used to form an electrode, such as a cathode of a battery, capacitor, or other energy storage device. The particulate carbon may be any form of carbon that has a small size and a high surface area. The particulate carbon may have an average particle size (i.e. the number average diameter) of less than 1 µm, such as less than 500 nm, less than 200 nm, less than 100 nm, or less than 50 nm. The average particle size (i.e. the number average diameter) can be determined using any known technique. Examples of techniques used to determine average particle size include, but are not limited to, Laser Diffraction, Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM), and Sieve Analysis.

[0072] The particulate carbon may have a Brunauer-Emmett-Teller (BET) surface area of greater than 5 m2 / g, such as greater than 10 m2 / g, greater than 50 m2 / g, greater than 100 m2 / g, greater than 200 m2 / g, greater than 500 m2 / g, greater than 1000 m2 / g, or a combination thereof, or in a range between any two of the aforementioned values. Brunauer-Emmett-Teller (BET) surface area analysis is a multi-point measurement 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 selected from carbon black (e.g. conductive carbon black, furnace black, thermal black, channel black, acetylene black, and lamp black), hard carbon, activated carbon, charcoal, coke, graphite, graphene, carbon nanotubes (e.g. Single-Walled Carbon Nanotubes (SWCNTs), Multi-Walled Carbon Nanotubes (MWCNTs), and Double-Walled Carbon Nanotubes (DWCNTs)), carbon nanofibers, or combinations thereof.

[0073] When the particulate carbon comprises carbon black, it may be selected from conductive carbon black, furnace black, thermal black, channel black, acetylene black, lamp black, or a combination thereof. It may be the case that the carbon black is conductive carbon black, such as C65, which has a surface area of around 65 m2 / g, or C45, which has a surface area of around 45 m2 / g. When the carbon source comprises carbon black, it may be the case that the average particle size (i.e. number average diameter) is in the range 10 µm to 40 µm, often in the range 20 µm to 70 µm, often in the range 30 µm to 50 µm. The average particle size (i.e. the number average diameter) can be determined using any known technique described herein.

[0074] When the carbon source comprises graphite, it may be the case that the average particle size (i.e. number average diameter) is in the range 10 µm to 100 µm, often in the range 20 µm to 70 µm, often in the range 30 µm to 50 µm. The average particle size (i.e. the number average diameter) can be determined using any known technique described herein.

[0075] When the carbon source comprises graphene, it may be the case that the average particle size (i.e. the number average diameter) is in the range 30 nm to 200 nm, often 50 nm to 150 nm, often 70 nm to 120 nm. The average particle size (i.e. the number average diameter) can be determined using any known technique described herein.

[0076] When the carbon source comprises carbon nanotubes, the carbon nanotubes may comprise Single-Walled Carbon Nanotubes (SWCNTs), Multi-Walled Carbon Nanotubes (MWCNTs), Double-Walled Carbon Nanotubes (DWCNTs), or combinations thereof. The carbon nanotubes may have an average particle size (i.e. the number average diameter) in the range 0.5 nm to 20 nm.

[0077] Where the carbon nanotubes consist of Single- Walled Carbon Nanotubes (SWCNTs), it may be the case that the average particle size (i.e. the number average diameter) is in the range 0.5 nm to 2.0 nm, often in the range 0.75 nm to 1.5 nm. Where the carbon nanotubes consist of Multi-Walled Carbon Nanotubes (MWCNTs), it may be the case that the average particle size (i.e. the number average diameter) is in the range 5 nm to 20 nm, often in the range 8 nmto 15nm. Where the carbon nanotubes consist of Double-Walled Carbon Nanotubes (DWCNTs), it may be the case that the average particle size (i.e. the number average diameter) is in the range 10 nm to 20 nm, often in the range 12 nm to 18 nm. The average particle size (i.e. the number average diameter) can be determined using any known technique described herein.

[0078] When the carbon source comprises carbon nanofibers, it may be the case that the average length of the nanofibers is in the range 5 µm to 100 µm and the average diameter of the nanofibers is in the range 5 nm to 100 nm. The average fibre length and average fibre diameter can be determined using any known technique. An example of a technique used to determine average fibre length and average fibre diameter includes, but is not limited to, Atomic Force Microscopy (AFM).

[0079] The particulate carbon may be selected from carbon black, carbon nanotubes, graphite, graphene, carbon nanofibers, or a combination thereof. It may be the case that the particulate carbon is selected from carbon black, carbon nanotubes, graphene, graphite, or combinations thereof.

[0080] The carbon source may be selected from polyethylene (PE), high modulus polyethylene, (HMPE), high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), high modulus polypropylene (HMPP), high density polypropylene (HDPP), low density polypropylene (LDPP), polyethylene terephthalate (PET), coal tar pitch, asphalt, bitumen, carbon black (e.g. conductive carbon black), carbon nanotubes, graphene, graphite, methane, or a combination thereof.

[0081] The carbon source may be selected from high modulus polyethylene (HMPE), high density polyethylene (HDPE), low density polyethylene (LDPE), high modulus polypropylene (HMPP), high density polypropylene (HDPP), low density polypropylene (LDPP), polyethylene terephthalate (PET), coal tar pitch, carbon nanotubes, carbon black (e.g. conductive carbon black), or combinations thereof.

[0082] The carbon source may be selected from polyethylene (PE) high modulus polyethylene, (HMPE), high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), high modulus polypropylene (HMPP), high density polypropylene (HDPP), low density polypropylene (LDPP), polyethylene terephthalate (PET), coal tar pitch, asphalt, bitumen, methane, or a combination thereof.The carbon source may comprise coal tar pitch and high modulus polyethylene. The carbon source may comprise particulate carbon and high modulus polyethylene. The carbon source may comprise coal tar pitch and high modulus polypropylene. The carbon source may comprise bitumen and high modulus polyethylene. The carbon source may comprise bitumen and high modulus polypropylene. The carbon source may comprise coal tar pitch, particulate carbon, and high modulus polyethylene. The carbon source may comprise coal tar pitch, particulate carbon, and high modulus polypropylene. The carbon source may comprise bitumen, particulate carbon, and high modulus polypropylene.

[0083] When the carbon source comprises particulate carbon (such as carbon black, conductive carbon, graphite, or carbon nanotubes) and a carbon-containing polymer (such as PE, HMPE, or HMPP), for instance, HMPE and carbon nanotubes, the particulate carbon and carbon-containing polymer 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.

[0084] When the carbon source comprises pitch (such as coal tar pitch or bitumen) and a carbon-containing polymer (such as PE, HMPE, or HMPP), 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.

[0085] The method according to the first and second aspects of the invention may provide a metal-carbon composite having a total carbon content in the range 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 metal-carbon composite has a total carbon content in the range 1 to 5% by weight carbon.

[0086] The method according to the second aspect of the invention may provide a carbon-coated metal-containing compound having a total carbon content in the range 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 in the range 1 to 5% by weight carbon. The total carbon content includes both the carbon present in the carbon coating and any carbon within the metal-containing compound.

[0087] The mixture comprises one or more alkali metal precursor compound(s). As used herein, the term “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 thereaction of the method. The metal may be in ionic form or neutral form and may be selected from Li, Na, K, Rb, Cs or Fr, preferably, Li, K or Na. The alkali metal precursor compound contributes an alkali metal atom to the metal-containing compound produced by the method according to the first and second aspects of the invention.

[0088] The alkali metal precursor compound used in the method according to the first and second aspects of the invention can be any compound that contains one or more alkali metals, such as lithium, sodium, potassium, rubidium, caesium, or francium; preferably, lithium, sodium or potassium; preferably, lithium or sodium; and more preferably, lithium. Examples of suitable alkali metal 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 any combination thereof. The alkali metal precursor compound may be selected 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 may comprise one or more compound(s) or hydrate(s) thereof selected from lithium dihydrogen phosphate (LiH₂PO₄), lithium phosphate (Li₃PO₄), lithium metaphosphate (LiPO₃), lithium carbonate (Li₂CO₃), lithium sulfate (Li₂SO₄), lithium hydrogen phosphate (Li₂HPO₄), and lithium hydroxide (LiOH). Preferably, the alkali metal precursor compound comprises LiH₂PO₄ or Li₂CO₃.

[0089] The metal precursor compound(s) used in the method according to the first and second aspects of the invention can be any compound that contains one or more metals, such as transition metals, non-transition metals, or metalloids, in their chemical structure. The metal in the metal precursor compound can have an initial average oxidation state, which can be zero or a positive integer. 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 any combination thereof. The metal precursor compound can provide the metal element for the metalcontaining compound produced by the method according to the first and second aspects of the invention, which can act as an active material for the electrode material. The metal precursor compound(s) may 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.It may be the case that the one or more metal precursor compound(s) comprises iron and / or manganese. Both iron and manganese compounds contribute to the development of more sustainable, cost-effective, and high-performing battery technologies.

[0090] It may be the case that the one or more metal precursor compound(s) comprises iron. Iron is plentiful and cost-effective when compared to metals like cobalt. Use of iron helps minimise the environmental impact linked to the extraction and processing of rarer metals. Additionally, iron-based materials, such as lithium iron phosphate, are recognized for their thermal stability and safety. They also offer good energy density and long cycle life.

[0091] It may be the case that the one or more metal precursor compound(s) comprises manganese. Manganese is more plentiful and cost-effective compared to other transition metals. Additionally, manganese-based materials can be used in both lithium-ion and sodium-ion batteries, offering flexibility in battery design.

[0092] The one or more metal precursor compound(s) may be selected from one or more of iron (III) oxide (Fe2O3), iron (11,111) oxide (FesC ), iron (III) oxyhydroxide (FeOOH), hydrated iron (III) phosphate (FePC>4.xH2O), iron (III) phosphate (FePC ), iron (II) phosphate (Fes(PO4)2), hydrated iron (II) sulfate (FeSC>4.xH2O), iron (III) nitrate (Fe(NOs)3), iron (II) acetate (Fe(CH3CC>2)2), iron (III) 2,4-pentanedionate (Fe(C5H? O2)3 wherein x, y are >0), manganese(ll) carbonate (MnCCh), manganese(lll) oxide (Mn2Os), manganese(IV) oxide (MnC>2), and manganese(ll) hydroxide (Mn(OH)2).

[0093] Both the carbon source (i) and elemental iron and / or Fe-P waste slag may function as a reducing agent. Without being bound by theory, elemental iron and / or Fe-P waste slag typically function as reducing agents through a ferrothermal reduction pathway and the carbon source typically functions as a reducing agent via a carbothermal reduction pathway. As used herein, the term “reducing agent” refers to a substance that donates electrons to another substance in a chemical reaction, thereby reducing the oxidation state of that substance. In this process, the reducing agent itself becomes oxidized. During the heating process of the method according to the first and second aspects of the invention, the initial average oxidation state of the metal in the metal precursor compound is reduced. Without being bound by theory, the reducing agent primarily drives the reduction of the metal in the metal precursor compound. The incorporation of elemental iron and / or Fe-P waste slag provides for a ferrothermal assisted carbothermal reduction, permitting the use of low cost and readily available metal precursors. Moreover, it ensures complete utilisation of elemental iron in the reaction andallows for excess carbon to be used to provide excellent compressed density and so to render a highly conductive composite product. As a result, the phase pure carbon-coated metal containing composite products produced by the method of the invention have superior electrochemical performance. As used herein, the term “ferrothermal assisted carbothermal reduction” is intended to refer to reduction mechanisms comprising a blend of ferrothermal and carbothermal reduction routes. It is believed that in the presence of the elemental iron and / or Fe-P waste slag, the ferrothermal reduction pathway is favoured, with the carbothermal pathway acting to reduce any remaining iron oxides in the mixture from iron (III) to iron (II).

[0094] It will often be the case that the ferrothermal assisted carbothermal reduction reaction will comprise in the range 30% - 90%, often 40% - 80% or 50% - 70% carbothermal contribution to the reduction mechanism. Therefore, it may be the case that the reduction reaction mechanism comprises a blend of carbothermal and ferrothermal reduction, but not ferrothermal reduction only, and not carbothermal reduction only. At these ranges it has been found that the optimal balance between density and discharge capacity can be provided, this is believed to be, at least in part, as particle morphology changes with the amount of ferrothermal reduction in the reduction mechanism, promoting the production of larger particles with particle size distributions which pack more efficiently. In addition, when ferrothermal assisted carbothermal reaction mechanisms are employed in combination with the carbon excesses described above, the density and discharge capacities are yet further enhanced.

[0095] As used herein, the term “Fe-P waste slag” refers to a by-product generated during the steelmaking process, specifically from the dephosphorization of hot metal. It primarily consists of iron (Fe), phosphorus (P), and iron phosphides. In addition, other elements may be present, such as calcium (Ca), magnesium (Mg), zinc (Zn), and copper (Cu). The slag can be either air-cooled, forming a dense, crystalline product, or water-cooled, resulting in a glassy, amorphous material. The use of Fe-P waste slag is advantageous, as it provides a source of both iron and phosphorous in the final metal-carbon composite. Moreover, iron and phosphorous can both act as reducing agents.

[0096] The mixture comprises elemental iron and / or Fe-P waste slag (i.e. component (iv)). It may be the case that component (iv) of the mixture comprises elemental iron. Elemental iron (i.e. iron metal) acts as an effective reducing agent in the synthesis reaction and allows the use of low cost and readily available iron precursors to be employed.Component (iv) may further comprise elemental manganese. Not only would manganese act as an effective reducing agent, but it would also provide a source of manganese in the metalcontaining product. Lithium Manganese Iron Phosphate provides high energy density and improved performance while maintaining cost-effectiveness and good thermal stability, making it suitable for applications requiring more power, such as electrode active materials.

[0097] The elemental iron may be selected from iron powder, scrap iron, Direct Reduced Iron (DRI), or a combination thereof. It may be the case that the elemental iron is selected from iron powder and / or Direct Reduced Iron. Direct Reduced Iron may also be referred to as sponge iron and is used in green blast furnace technology. Elemental iron is abundant, and readily accessible. Moreover, scrap iron and Direct Reduced Iron in particular are very low cost, and may sometimes even includes a small amount of carbon, enhancing the conductivity of the resultant product.

[0098] The elemental iron and / or Fe-P waste slag may be in particulate form. It may be the case that the average particle size (i.e. the number average diameter) of elemental iron and / or Fe-P waste slag is in the range 1 pm to 1000 pm. It may be the case that the average particle size (i.e. the number average diameter) of elemental iron and / or Fe-P waste slag is in the range 1 pm to 500 pm. It may be the case that the average particle size (i.e. the number average diameter) of elemental iron and / or Fe-P waste slag is in the range 1 pm to 300 pm. It may be the case that the average particle size (i.e. the number average diameter) of elemental iron and / or Fe-P waste slag is in the range 1 pm to 150 pm. The average particle size (i.e. the number average diameter) of elemental iron and / or Fe-P waste slag can be determined using any known technique described herein. Examples of techniques used to determine average particle size include, but are not limited to, Laser Diffraction, Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM), and Sieve Analysis.

[0099] If the elemental iron is selected from DRI in agglomerate form, the method may include an additional step of pulverising the DRI into particles before forming the mixture.

[0100] When component (iv) further comprises manganese, it may be in particulate form. It may be the case that the average particle size (i.e. the number average diameter) of manganese is in the range 1 pm to 1000 pm. It may be the case that the average particle size (i.e. the number average diameter) of manganese is in the range 1 pm to 500 pm. It may be the case that the average particle size (i.e. the number average diameter) of manganese is in the range 1 pm to 300 pm. It may be the case that the average particle size (i.e. the number average diameter) of manganese is in the range 1 pm to 150 pm. The average particle size (i.e. the numberaverage diameter) of manganese can be determined using any known technique described herein. Examples of techniques used to determine average particle size of manganese include, but are not limited to, Laser Diffraction, Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM), and Sieve Analysis.

[0101] The method according to the first and second aspects of the invention includes heating the mixture under an inert atmosphere to produce a reaction product comprising the metal-carbon composite described herein. During heating step b), the initial average oxidation state of the one or more metals in the metal precursor compound is reduced. Without being bound by theory, elemental iron and / or Fe-P waste slag primarily drives the reduction of the metal in the metal precursor compound. Heating the mixture under an inert atmosphere is advantageous due to the prevention of oxidation of the metal precursor being reduced, ensuring a cleaner and more efficient process. It also allows for precise control over the chemical environment, reducing unwanted side reactions. The method according to the first aspect and second aspect of the invention enhances the quality of the final product by minimising impurities, and producing phase pure metal-carbon composites comprising metal-containing products and carbon. It is also more energy-efficient, often requiring lower temperatures. It may be the case that heating the mixture in step b) takes place under nitrogen gas and / or argon gas.

[0102] It may be the case that heating step b) takes place at a temperature in the range 200 °C to 1500 °C, often in the range 300 °C to 1000 °C, often in the range 450 °C to 900 °C, often in the range 500 °C to 800 °C. The temperature may be maintained for a period in the range 240 minutes (i.e. 4 hours) to 600 minutes (i.e. 10 hours), often for a period in the range 300 minutes (i.e. 5 hours) to 540 minutes (i.e. 9 hours). The heating may comprise a ramped increase in temperature, for example, at a heating rate of 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, after which the heating may be maintained at that temperature. Ramping the temperature in this manner can result in a more uniform carbon coating on the metal-containing compound.

[0103] When the carbon source comprises pitch and / or a carbon-containing polymer, it may be the case that heating step b) is a multi-step heating step. For instance, the heating step b) may include heating the mixture at a first temperature proximate to or above the melting point of the pitch and / or carbon-containing polymer. This may permit the pitch and / or carbon-containing polymer to melt over and coat the metal particles. After heating at the first temperature, the mixture can be heated at a second temperature that is sufficient to convert the pitch and / or carbon-containing polymer to carbon (i.e. pyrolysis).The temperature of the first step (i.e. the first temperature) may be selected to correspond to the softening and / or melting point of the pitch and / or carbon-containing polymer, and the temperature of the second step may be selected to correspond to the temperature of pyrolysis. The first temperature (i.e. the temperature proximate to or above the melting point of the pitch and / or carbon-containing polymer) can vary depending on the type and composition of the pitch and / or carbon-containing polymer used. With regard to the type of pitch selected, depending on its composition and viscosity, the first temperature can be in the range of 50 °C to 250 °C, such as 70 °C to 100 °C, or 100 °C to 200 °C. With regard to the carbon-containing polymer selected, if the carbon-containing polymer is a polyethylene (PE), the first temperature can be in the range of 120 °C to 130 °C. If the carbon-containing polymer is a polyethylene glycol (PEG), the first temperature can be in the range of 50 °C to 70 °C, depending on the length of the carbon-containing polymer. If the carbon-containing polymer is a polypropylene (PP), the first temperature can be in the range of 160 °C to 171 °C. If the carbon-containing polymer is a polyvinyl alcohol (PVA), the first temperature can be in the range of 150 °C to 200 °C. The temperature of this first aspect of the heating step can be in the range of 50 °C to 250 °C. The first temperature may be maintained for a period 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.

[0104] Optionally, the second temperature can be in the range of 300 °C to 1500 °C, depending on the type and composition of the pitch and / or carbon-containing polymer and precursor material. The second temperature range may be from 300 °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. Heating to the second temperature may comprise a ramped increase in temperature, for example, at a heating rate of 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 second temperature may be ramped until the desired temperature is reached, after which the heating may be maintained at that temperature. The duration of heating at the second temperature can vary depending on the amount and size of the particles in the mixture but can be in the range of 1 to 500 minutes. The second temperature may be maintained for a period of 1 to 500 minutes, such as 10 to 450 minutes, 50 to 400 minutes, 100 to 350 minutes, 200 to 350 minutes, 250 to 350 minutes, or in a range constituted by any two of the aforementioned minute values.

[0105] Improved coating of the metal particles may be achieved by having a two-step heating process, wherein the particles can be coated with molten pitch and / or carbon-containing polymer in the first heating step, and then the pitch and / or carbon-containing polymer ispyrolyzed to form a carbon coating on the particles in the second step. This two-step heating can ensure a uniform distribution of the molten pitch and / or carbon-containing polymer on the surface of the particles and prevent agglomeration.

[0106] At least part of the pitch and / or carbon-containing polymer is converted to elemental carbon during heating at the second temperature. For example, at least part of the pitch and / or carbon-containing polymer is converted to sp2hybridized carbon, which can have a higher electrical conductivity and a lower resistance than other forms of carbon. The conversion of the pitch and / or carbon-containing polymer to sp2carbon can be influenced by the temperature and duration of heating at the second temperature. At least part of the sp2carbon can be graphitic, in which it can be described as “graphitic sp2hybridised carbon” or “networked sp2hybridised carbon". At least part of the pitch and / or carbon-containing polymer can be converted to a graphite-like honeycomb network.

[0107] It may be the case that at least part of the pitch and / or carbon-containing polymer is converted to elemental carbon during heating at the second temperature. It may be the case that at least part of the carbon source is converted to sp2carbon.

[0108] Where the carbon source comprises pitch and / or a carbon-containing polymer, the method may further comprise contacting the mixture with a reducing gas during heating step b). Optionally, the reducing gas may be selected from CO, H2, and combinations thereof. The reducing gas may assist in reducing the metal precursor compound and thereby accelerate the reaction. Advantageously, the reducing gas may be generated in situ during pyrolysis of the pitch and / or a carbon-containing polymer. Alternatively, the reducing gas may be added to the reaction mixture prior to or during heating.

[0109] The method according to the first and second aspects of the invention may further comprise the step of pelletising the mixture prior to the heating step b). Pelletisation offers several advantages, such as improved handling, transportation, and storage due to the uniform shape and size of the pellets. It also reduces dust generation, enhancing workplace safety and cleanliness.

[0110] It may be the case that the method according to the first and second aspects of the invention described herein includes an additional step prior to formation of the mixture, the additional step comprising drying the one or more alkali metal precursor(s) and the one or more metal precursor(s). This additional step ensures that moisture content of the mixture is as low as possible, enhancing the efficiency of the method. It may be the case that the drying step takesplace at a temperature in the range 100 °C to 300 °C, often in the range 150 °C to 250 °C. It may be the case that the drying stage takes place under vacuum. In the event that the drying stage takes place under vacuum, the temperature may be in the range 100°C to 200 °C. The duration of the drying stage may be in the range 45 minutes to 90 minutes, often 60 minutes.

[0111] It may be the case that the method according to the first and second aspects of the invention described herein includes an additional step after heating step b), the step comprising pulverising the sample. Finely pulverised materials mix more uniformly with other components in preparation of an electrode for example, resulting in a consistent and homogeneous end product.

[0112] The metal-containing compound produced by the method according to the first and second aspects of the invention may have the formula:

[0113] AaMb(XcYd)eZf

[0114] wherein:

[0115] A is an alkali metal selected from one or more of lithium, sodium and potassium;

[0116] M comprises iron and optionally one or more additional metals selected from transition metals, non-transition metals, and metalloids;

[0117] (XcYd)e is at least one first anion; and

[0118] Z is at least one second anion;

[0119] wherein a >0; b >0; c >0; d >0; e >0 and f >0;

[0120] wherein a, b, c, d, e and f are chosen to maintain electroneutrality;

[0121] 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.

[0122] Compounds of this formula are ideally suitable for use as electrode materials, and particularly as cathode materials in alkali metal batteries, such as Li-ion, Na-ion and K-ion batteries.

[0123] In the above formula, M comprises iron, and optionally one or more additional metals selected from titanium, vanadium, niobium, tantalum, hafnium, chromium, molybdenum, tungsten, manganese, 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.

[0124] In the above formula, f may be 0 and Z may be absent. Alternatively, it may be the case that Z is selected from one or more halides, hydroxide-containing groups and mixtures thereof.

[0125] In the above formula, X may comprise phosphorus.

[0126] In the above formula, (XcYd)e may be PO4 and / or a P2O7 moiety.

[0127] The metal-containing compound may be selected from one or more of the group consisting of LiFeP04, NaFeP04, LiMno.5Feo.2Mgo.3P04, LiFe0.iMn0.gPO4, LiFe0.2Mn0.8PO4, LiFe0.3Mn0.7PO4, LiFeo.4Mno.eP04, LiFeo.5Mno.5PO4, LiFeo.9sMgo osP04, LiFeo.9Mgo.1PO4, LiFeo.iMgo.osMno.8sP04, LiFeo.2Mgo.osMno.7sP04, Na4Fe3(PO4)2P2O7, LiMno.5Feo.5PO4, Na2Fe(SO4)2, Fe3(PO4)2, Na2FeP2O7, NaFeS04F, LiFeS04F, Li2Fe2(SO4)3, Li2Fe(SO4)2, Na2FePO4F, KFeP04.

[0128] It may be the case that the metal-containing compound has have the formula: LiMPC, where M comprises iron, and optionally one or more additional metals selected from manganese, cobalt, nickel, copper, zinc, magnesium, calcium and combinations thereof. It may be the case that the metal-containing compound has the formula: LiMPC, where M comprises iron and manganese. It may be the case that the metal-containing compound has the formula: LiMPCU, where M comprises iron, magnesium and manganese.

[0129] It may be the case that the metal-containing compound is selected from LiFePCU, LiFei.xMnxPCU, LiFei-xMgxPCU and UFe1-x-yMnxMgyPCU, wherein 0<x<1 and 0<y<1. If magnesium is included, it may often be present at less than 10 wt%, preferably less than 5 wt%.

[0130] Lithium Iron Phosphate (LFP) and Lithium Manganese Iron Phosphate (LMFP), along with Lithium Iron Manganese Magnesium Phosphate, are all prominent materials in battery technology, each offering unique benefits. Lithium Iron Phosphate is highly valued for its exceptional safety, long lifespan, low maintenance needs, and eco-friendliness, making it ideal for a wide range of applications. Lithium Manganese Iron Phosphate provides high energy density and improved performance while maintaining cost-effectiveness and good thermal stability, making it suitable for applications requiring high power. Lithium Iron Manganese Magnesium Phosphate, enhances structural stability and cycling performance while combining the benefits of both LFP and LMPF, thus providing an optimal balance of safety,energy density, and longevity. Each of these materials contribute to the development of safe, efficient, and sustainable battery solutions.

[0131] The metal-containing compound may include particulate carbon described herein. It may be the case that the metal-containing compound includes particulate carbon in addition to a carbon coating. This particulate carbon can act as a conductive filler, enhancing the electrical conductivity and stability of the electrode material. By connecting the metal-containing compound particles into an interconnected network, particulate carbon facilitates electron transport. Additionally, particulate carbon boosts the mechanical strength and integrity of the electrode material by bridging gaps between particles and reducing stress concentrations. It further increases the specific capacity and rate performance of the electrode material.

[0132] The present invention extends to an electrode active material containing the metal-carbon composite described herein. In a third aspect of the invention there is provided an electrode active material made according to the method according to the first aspect and second aspect of the invention.

[0133] In a fourth aspect of the invention there is provided a composition comprising LiFePO₄ in particulate form made according to the method according to the second aspect of the invention, wherein the particles are at least partially coated with a carbon coating, and wherein at least a portion of the carbon coating comprises sp2carbons. The LiFePC particles produced by the methods described have been found to have good morphology, and particle size distributions, allowing excellent packing and so high compression densities; together with excellent electrochemical properties. In addition, the methods described provide for high phase purity in the particles. This combination of features provides for a unique LiFePO₄ product.

[0134] In a fifth aspect of the invention, there is provided a composition comprising LiFe₁₋ₓMnₓPO₄ in particulate form made according to the method according to the second aspect of the invention, wherein the particles are at least partially coated with a carbon coating, and wherein at least a portion of the carbon coating comprises sp2carbons. This composition, comprising LiFe₁₋ₓMnₓPO₄ particles which have, by virtue of the methods used to prepare them, excellent phase purity and electrochemical properties, provides for a unique LiFe₁₋ₓMnₓPO₄ product.

[0135] In a sixth aspect of the invention, there is provided a battery comprising an electrode comprising a metal-carbon composite made according to the method according to the first aspect and second aspect of the invention. It may be the case that the battery is arechargeable battery. It may be the case that the battery is an alkali metal ion battery, such as a lithium-ion battery. Batteries according to the sixth aspect of the invention are sustainable, cost-effective, and high-performing.

[0136] 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. Preferably, the alkali metal ion battery is a lithium-ion battery.

[0137] Rechargeable batteries typically comprise an anode, a cathode, a separator, and an electrolyte. The anode is the negative electrode that releases electrons to an external circuit during discharge and the cathode is the positive electrode that receives electrons from the external circuit during discharge. The separator is typically a porous membrane that prevents direct contact between the anode and the cathode while allowing the passage of ions therebetween. The electrolyte is a liquid, solid, or gel medium that facilitates the transport of ions between the anode and the cathode.

[0138] 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.

[0139] 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 bondedto 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.

[0140] 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 a protective layer on the electrode surface. The amount of the solvent, the salt, and the additive can vary depending on the desired viscosity, conductivity, and electrochemical properties of the electrolyte.

[0141] In a seventh aspect of the invention, there is provided a use of a metal-carbon composite made according to the method according to the first aspect and second aspect of the invention as an electrode in a rechargeable battery. It may be the case that the battery is an alkali metal ion battery. It may be the case that the battery is a lithium-ion battery. Use of metal-carbon composites produced by the method according to the first aspect and second aspect of the invention contribute to the development of more sustainable, cost-effective, and high-performing battery technologies.

[0142] In an eighth aspect of the invention, there is provided a use of a carbon source comprising a carbon-containing polymer, pitch, particulate carbon, a hydrocarbon, or combinations thereof,and elemental iron and / or Fe-P waste slag in a ferrothermal assisted carbothermal reduction reaction of a metal precursor compound to produce a metal-carbon composite. As noted above, it will often be the case that the ferrothermal assisted carbothermal reduction reaction will comprises in the range 30% - 90% often 40% - 80% or 50% - 70% carbothermal contribution to the reduction mechanism.

[0143] In a nineth aspect of the invention, there is provided a use of a carbon source comprising a carbon-containing polymer, pitch, a hydrocarbon, biomass, or combinations thereof, and elemental iron and / or Fe-P waste slag in a ferrothermal assisted 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 sp2carbons.

[0144] Use of the carbon source as defined herein in combination with elemental iron and / or Fe-P waste slag provides a ferrothermal assisted carbothermal reduction, permitting the use of low cost and readily available metal precursors. Moreover, it ensures complete utilisation of elemental iron in the reaction and allows for excess carbon to be used to render a highly conductive composite product. In particular, use of a carbon source comprising a carbon-containing polymer, pitch, a hydrocarbon, biomass, or combinations thereof, with elemental iron and / or Fe-P waste slag provides phase pure carbon-coated metal containing composite products having superior electrochemical performance.

[0145] The advantages of the second, third, fourth, fifth, sixth, seventh, eighth, and nineth aspects may correspond to those of the first aspect where applicable.

[0146] 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, although all aspects of the invention preferably “comprise” the features described in relation to that aspect, it is specifically envisaged that they may “consist” or “consist essentially” of those features outlined in the claims. In addition, all terms, unless specifically defined herein, are intended to be given their commonly understood meaning in the art.

[0147] 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 imply the 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 composition or 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.

[0148] 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.

[0149] 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±9 wt%, 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.

[0150] In order that the invention may be more readily understood, it will be described further with reference to the figures and to the specific examples hereinafter.

[0151] In the accompanying Figures:

[0152] Figure 1A is an XRD diagram of a sample prepared according to Comparative Example 1 (ID: R1002). The intensity in arbitrary units (AU) can be found along the y-axis, which refers to the relative measure of the strength of the diffracted X-ray signal, and two-theta (20) can be found along the x-axis, which represents the angle between the incident X-ray beam and the diffracted beam.

[0153] Figure 1B shows the constant current data for the LiFePO₄ cathode active material of Comparative Example 1 (made using LiH₂PO₄, Fe₂O₃ and C65 particulate carbon). Specifically, Figure 1 B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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 2A is an XRD diagram of a sample prepared according to Comparative Example 2 (ID: R1241). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0154] Figure 2B shows the constant current data for the LiFePO₄ cathode active material of Comparative Example 2 (made using LiH₂PO₄, Fe₂O₃ and iron metal powder). Specifically, Figure 2B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0155] Figure 3A is an XRD diagram of a sample prepared according to Comparative Example 3 (ID: R1115). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0156] Figure 3B shows the constant current data for the LiFePO₄ cathode active material of Comparative Example 3 (made using LiH₂PO₄, Fe₂O₃ and iron metal powder). Specifically, Figure 3B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0157] Figure 4 is an XRD diagram of a sample prepared according to Comparative Example 4 (ID: R1118). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0158] Figure 5A is an XRD diagram of a sample prepared according to Comparative example 5 (ID: R1769). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0159] Figure 5B shows the constant current data for the LiFePO₄ cathode active material of Comparative example 5 (made using LiH₂PO₄, Fe₂O₃, iron metal powder, and HMPE). Specifically, Figure 5B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). The current density was set to an equivalent rate of C / 10assuming 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).

[0160] Figure 6A is an XRD diagram of a sample prepared according to Comparative example 6 (ID: R1513). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0161] Figure 6B shows the constant current data for the LiFePO₄ cathode active material of Comparative example 6 (made using LiH₂PO₄, Fe₂O₃, iron metal powder, and HMPE). Specifically, Figure 6B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0162] Figure 7A is an XRD diagram of a sample prepared according to Comparative example 7 (ID: R1511). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0163] Figure 7B shows the constant current data for the LiFePO₄ cathode active material of Comparative example 7 (made using LiH₂PO₄, Fe₂O₃, iron metal powder, and HMPE). Specifically, Figure 7B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0164] Figure 8A is an XRD diagram of samples prepared according to Examples 1a, 1b and 1c (ID: R1254, R1691 and R1707). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0165] Figure 8B shows the constant current data for the LiFePO₄ cathode active material of Example 1 (made using LiH₂PO₄, Fe₂O₃, iron metal powder, and high modulus polyethylene powder (HMPE)). Specifically, Figure 8B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). The current density was set to an equivalent rateof 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).

[0166] Figure 9A is an XRD diagram of a sample prepared according to Example 2 (ID: R1243). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0167] Figure 9B shows the constant current data for the LiFePO₄ cathode active material of Example 2 (made using LiH₂PO₄, Fe₂O₃, iron metal powder, and coal tar pitch (CTP)). Specifically, Figure 9B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0168] Figure 10 is an XRD diagram of a sample prepared according to Example 3 (ID: R1116). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0169] Figure 11 A is an XRD diagram of a sample prepared according to Example 4 (ID: R1117). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0170] Figure 11 B shows the constant current data for the LiFePO₄ cathode active material of Example 4 (made using LiH₂PO₄, Fe₂O₃, atomised iron metal, and high modulus polyethylene powder (HMPE)). Specifically, Figure 11B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0171] Figure 12 shows the constant current data for the LiFePO₄ cathode active material of Example 5 (ID: R1270) (made using LiH₂PO₄, Fe₂O₃, iron metal powder, high modulus polyethylene powder (HMPE), and Multi-Walled Carbon Nanotubes). Specifically, Figure 12 shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAhg-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). The current density was set to an equivalent rate of C / 10 assuming a reversible specific capacityof 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).

[0172] Figure 13A is an XRD diagram of a sample prepared according to Example 6 (ID: R1280). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0173] Figure 13B shows the constant current data for the LiFePO₄ cathode active material of Example 6 (made using LiH₂PO₄, Fe₂O₃, iron metal powder, and coal tar pitch (CTP)). Specifically, Figure 13B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0174] Figure 14 is an XRD diagram of a sample prepared according to Example 7 (ID: M1025). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0175] Figure 15 is an XRD diagram of a sample prepared according to Example 8 (ID: M1026). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0176] Figure 16 is an XRD diagram of a sample prepared according to Example 9 (ID: M1027). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0177] Figure 17 is an XRD diagram of a sample prepared according to Example 10 (ID: M1059). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0178] Figure 18A is an XRD diagram of a sample prepared according to Example 11 (ID: R1266). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0179] Figure 18B shows the constant current data for the LiFePO₄ cathode active material of Example 11 (made using LiH₂PO₄, Fe₂O₃, iron metal powder, and petroleum pitch).Specifically, Figure 18B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0180] Figure 19A is an XRD diagram of a sample prepared according to Example 12 (ID: R1773). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0181] Figure 19B shows the constant current data for the LiFePO₄ cathode active material of Example 12 (made using LiH₂PO₄, Fe₂O₃, iron metal powder, and HMPE). Specifically, Figure 19B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0182] Figure 20A is an XRD diagram of a sample prepared according to Example 13 (ID: R1787). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0183] Figure 20B shows the constant current data for the LiFePO₄ cathode active material of Example 13 (made using LiH₂PO₄, Fe₂O₃, iron metal powder, and HMPE). Specifically, Figure 20B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0184] Figure 21A is an XRD diagram of a sample prepared according to Example 14. The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0185] Figures 21 B and 21 C show the constant current data for the LiFePO₄ cathode active material of the samples of Example 14 (made using LiH₂PO₄, Fe₂O₃, iron metal powder, and HMPE at various CTFT ratios). Specifically, Figures 21B and 21C show the voltage profile (electrodepotential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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). In Figure 21 B the ferrothermal route is indicated by a solid line, 10% CT by a dashed line, 20% CT by a dotted line, and 30% CT by a combination of dots and dashes. In Figure 21C, 40% CT is indicated by a solid line, 50% by a dashed line, 70% by a dotted line, and 90% by a combination of dots and dashes.

[0186] Figure 22A is an XRD diagram of a sample prepared according to Example 15. The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0187] Figures 22B and 22C show the constant current data for the LiFePO₄ cathode active material of Example 15 (made using UH2PO4, Fe2Os, iron metal powder, and HMPE at various CT: FT ratios). Specifically, Figures 22B and 22C show the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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). In Figure 22B the ferrothermal route is indicated by a solid line, 10% CT by a dashed line, and 30% CT by a dotted line. In Figure 22C, 50% CT is indicated by a solid line, 70% by a dashed line, and 90% by a dotted line.

[0188] Figure 23A is an XRD diagram of a sample prepared according to Example 16. The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0189] Figures 23B and 23C show the constant current data for the LiFePO₄ cathode active material of Example 16 (made using UH2PO4, Fe2Os, iron metal powder, and HMPE at various CT: FT ratios). Specifically, Figures 23B and 23C show the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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). In Figure 23B the ferrothermal route is indicated by a solid line, 10% CT by a dashed line, and30% CT by a dotted line. In Figure 23C, 50% CT is indicated by a solid line, 70% by a dashed line, and 90% by a dotted line.

[0190] Figure 24A is an XRD diagram of a sample prepared according to Example 17 (ID: R1695). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0191] Figure 24B shows the constant current data for the LiFePO₄ cathode active material of Example 17 (made using UH2PO4, Fe2Os, iron metal powder, and HMPE). Specifically, Figure 24B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0192] Figure 25A is an XRD diagram of a sample prepared according to Example 18 (ID: R1776). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0193] Figure 25B shows the constant current data for the LiFePO₄ cathode active material of Example 18 (made using UH2PO4, Fe2Os, iron metal powder, and HMPE). Specifically, Figure 25B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0194] Figure 26A is an XRD diagram of a sample prepared according to Example 19 (ID: R1777). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0195] Figure 26B shows the constant current data for the LiFePO₄ cathode active material of Example 19 (made using UH2PO4, Fe2Os, iron metal powder, and HMPE). Specifically, Figure 26B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). The current density was set to an equivalent rate of C / 10 assuming areversible 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).

[0196] Figure 27A is an XRD diagram of a sample prepared according to Example 20 (ID: R1778). The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.

[0197] Figure 27B shows the constant current data for the LiFePO₄ cathode active material of Example 20 (made using UH2PO4, Fe2Os, iron metal powder, and HMPE). Specifically, Figure 27B shows the voltage profile (electrode potential [V vs. Li / Li+] along the y axis versus specific capacity [mAh g-1] along the x axis) for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0198] Figure 28 shows the constant current data for the LiFePO₄ cathode active material of samples made under ferrothermal reduction mechanisms. Specifically, Figure 28 shows the tap density (g / cm³) along the y axis versus the specific capacity [mAhg⁻¹] along the x axis for cycle 2 (i.e. following one complete charge and discharge cycle). 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).

[0199] Figure 29 shows the constant current data for the LiFePO₄ cathode active material of samples made under carbothermal reduction. Specifically, Figure 29 shows the specific capacity [mAhg⁻¹] along the y axis for cycle 2 (i.e. following one complete charge and discharge cycle) versus C molexcess. 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).

[0200] Figures 30A, 30B and 30C show the XRD data for a test series based on the cathode active materials of carbothermal-ferrothermal blend samples in the series of Example samples 14, 15 and 16, and comparative examples 5, 6 and 7 where CT% is 100% (Figure 30A for CT: FT 0.00 Cexcesswt%, Figure 30B for CT: FT 1.58 Cexcesswt% and Figure 30C for CT:FT 3.16 Cexcess wt%) The intensity in arbitrary units (AU) can be found along the y-axis, and two-theta (20) can be found along the x-axis.Figure 31 shows the constant current data for the LiFePO₄ cathode active material of samples made under carbothermal-ferrothermal reduction mechanisms (Example samples 14, 15 and 16, and comparative examples 4, 5 and 6 where CT% is 100%). Specifically, Figure 31 shows the specific capacity [mAhg⁻¹] along the y axis for cycle 2 (i.e. following one complete charge and discharge cycle) versus CT% across the range 0% to 100% for pure FT - 0 Cexcess wt% (diamonds) together with blend reactions at 0 Cexcess wt% (dots), 1.58 Cexcess wt% (squares) and 3.16 Cexcesswt% (triangles). 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).

[0201] Figure 32 shows the compressed density for the samples of Figure 31, specifically, CT% across the range 0% to 100% for pure FT - 0 Cexcess wt% (diamonds) together with blend reactions at 0 Cexcess wt% (dots), 1.58 Cexcess wt% (squares) and 3.16 Cexcess wt% (triangles).

[0202] Figure 33 shows the tap density for the samples of Figures 31 and 32, specifically, CT% across the range 0% to 100% for pure FT - 0 Cexcess wt% (diamonds) together with blend reactions at 0 Cexcesswt% (dots), 1.58 Cexcess wt% (squares) and 3.16 Cexcess wt% (triangles).

[0203] Figures 34A and 34B are scanning electron microscope images (10kx magnification) providing a comparison between the particle sizes produced by ferrothermal reduction mechanisms (34A) and 50:50 CT: FT mechanisms (34B) at 0 Cexcess wt% ■

[0204] Figure 35 shows a plot of particle size (D50) on the y axis against reduction mechanism by %CT, together with scanning electron microscope images (10kx magnification) providing a comparison between the particle sizes produced by ferrothermal reduction mechanism (top middle), 50:50 (top right), 70:30 (bottom left), 90:10 (bottom middle) CT: FT mechanisms and a sample produced entirely by carbothermal reduction (1.58 Cexcess wt%) (bottom right).

[0205] Figure 36 shows the particle size distribution for the samples of Figure 33, plotting probability density against particle diameter in pm. The boxplot below the probability density profile shows spans between the 5th to 95th percentile (D5 to D95), the box extent between the 25th to 75th percentile, the median line (D50) and datapoints outside the span denoted by circles for the samples of Figure 35. In Figure 36, sample R1773 is shown as a solid line, R1776 as a dashed line formed of short dashes, R1777 as a dotted line, R1778 as a combination of dots and dashes, and R1513 as a dashed line formed of long dashes with wide gaps.EXAMPLES

[0206] General Method

[0207] 1. The starting materials were intimately mixed in the correct stoichiometric proportions and pressed into a pellet.

[0208] 2. The resulting pelletized mixture was placed inside a furnace under an inert atmosphere at a furnace temperature of between 300°C and 900°C until a product was formed. 3. The product were allowed to cool under an inert atmosphere before grinding to a powder.

[0209] Abbreviations

[0210] RMM = relative molecular mass

[0211] Product Analysis using powder X-ray Diffraction (XRD)

[0212] 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.

[0213] The XRD operating conditions are as follows:

[0214] X-ray source: CuKα

[0215] X-ray wavelength: 1.5418 angstroms (A)

[0216] Typical 20 range: 20 = 10 to 65°

[0217] Product Analysis using Scanning Electron Microscopy (SEM)

[0218] Analysis by SEM was conducted using a Zeiss Evo MA10. The electron beam accelerating voltage was 10kV. The images were taken at 10kx magnification. Particle diameter values from SEM images were measured from segmented particles within the field of view.

[0219] Electrochemical Results

[0220] The target materials were tested in metallic lithium half cells which can be made using the following procedure. The materials synthesized (active materials) were made into positive electrodes. The positive electrode was prepared by solvent casting a slurry of the activematerial, conductive carbon, binder and binder solvent. The conductive carbon used was C65 (Imerys). PVdF-HFP co-polymer (Sigma-Aldrich) was used as the binder and acetone was employed as the binder solvent. The slurry was then cast into a glass plate and a free-standing electrode was formed as the solvent evaporated. The electrode was then dried further at 80 °C 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 be used as the contact to the active material. Metallic lithium was used as the negative electrode material. Optionally a copper current collector may be used as the contact to the lithium material. The electrolyte comprised 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 negative electrodes.

[0221] The cells were tested as follows. The cells were tested at room temperature. For constant current cycling, the cell was cycled at a given (low rate) current density between pre-set voltage 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. This method provided a voltage (versus the Li reference potential) versus specific capacity profile for the active material under investigation. This approach can be extended over multiple charge-discharge cycles to provide a long-term cycle stability test.

[0222] 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 incorporated herein by reference. EVS is a voltage step method which provides a high-resolution approximation to the open circuit voltage curve (versus the Li reference potential) for the electrochemical system under investigation. Similarly to the constant current testing, this EVS method provided a voltage (versus the Li reference potential) versus specific capacity profile for the active material under investigation. The complementary differential capacity data 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 customsoftware and commercial voltage generator (Advantest) and current monitoring equipment (Hewlett Packard).

[0223] Reaction Mechanisms

[0224] Carbothermal reaction

[0225] There are two carbothermal reaction mechanisms, one where the byproduct is carbon monoxide and one where the byproduct is carbon dioxide. It is possible that many carbothermal reduction mechanisms combine a mixture of both mechanisms. However, for the purposes of the calculations in this document it is assumed that only the carbon monoxide producing mechanism is followed.

[0226] A carbothermal reaction, where all carbon produces CO, is given by:

[0227] 0.5Fe2O3+ LiH2PO4+ 0.5C → LiFePO4+ H2O + 0.5CO

[0228] This reaction has a 0% carbon (C) molar excess percent. The carbon molar excess percent, Cmoiexcess%, in the carbothermal reaction is given by

[0229] Cmolexcess% = ((molc - molFe2O3) / molFe2O3) * 100

[0230] Cmolexcess% = * 100

[0231]

[0232] motFe2O3

[0233] Ferrothermal reaction in the presence of carbon

[0234] A ferrothermal reaction in the presence of carbon, assuming that all carbon forms carbon monoxide is given by:

[0235] 0.4Fe2O3+ 0.2Fe + LiH2PO4+ 0.2C → LiFePO4+ H2O + 0.2CO

[0236] This ferrothermal reaction has a 0% carbon (C) molar excess percent (Cmoiexcess %).

[0237] Blended reaction pathways and CT: FT ratio

[0238] Where both ferrothermal (FT) and carbothermal (CT) reduction mechanisms are in operation, these can be defined by relative ratios of activity (the CT: FT ratio). As the ferrothermal reduction is preferred, it will generally go to completion with the carbothermal reduction mechanism commencing when the iron is depleted. The CT: FT ratio is the proportion of iron oxide which is reduced by the carbon via the carbothermal reduction mechanism. For instance, a 0% CT: FT ratio equates to complete reduction via the ferrothermal mechanism; a 100%CT: FT ratio equates to complete reduction via the carbothermal mechanism. A calculation of a 50:50 CT: FT is provided below:

[0239] 0.4444Fe2O3+ 0.1112Fe + 1.0000LiH2PO4+ 0.3333C → 1LiFePO4+ H2O + 0.3333CO

[0240] Mol Fe2O3reduced to Fe2+by:

[0241] Fe° 0.1112 *2 = 0.2223 mol

[0242] C 0.4444- 0.2223 = 0.2221 mol

[0243] CT: FT proportion is (0.2221 / (0.2221 +0.2223))*100

[0244] CT: FT ratio is 50%

[0245] Calculation of Carbon (C) Weight and Molar Percentage Excess

[0246] Carbon excess can be expressed in two ways. The first is based on the carbon molar percent excess. The second on a carbon weight percent excess as a proportion of all the reactants in the blended reaction.

[0247] For any blended reaction, assuming all Fe° is consumed in ferrothermal reduction of Fe3+to Fe2+(from Fe2O3) before any carbothermal reduction, the carbon molar excess, Cmolexcess, is given by:

[0248] C

[0249]

[0250] molexcess = molc— molFe— (molFeO— molFe* 2)

[0251] The carbon weight percent excess is then given by:

[0252] Cexcess wt%

[0253] Cmolexcess * RMMC

[0254]

[0255] molLHP* RMMLHP+ molFeO* RMMFeO+ molFe* RMMFe+ (molCtotal— Cmolexcess) * RMMC* 100

[0256] Synthetic Examples and Electrochemistry

[0257] Comparative Example 1 - LHP in the presence of iron (III) oxide, and Carbon (no elemental iron and / or Fe-P waste slag present) - R1002

[0258] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, and particulate carbon (C65)Synthesis Stoichiometric Reaction: LiH2PO4+ 0.5 Fe2O3+ 0.5 C → LiFePO4+ H2O + 0.5 CO2

[0259] Synthesis Precursor Recipe:

[0260] LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0261] Fe2O3[RMM = 159.7 g / mol] (g): 0.7985 g

[0262] Carbon: C65; 0.12 g

[0263] Synthesis Conditions:

[0264] Mixing Conditions: McCrone Micronizer, 20 mins Agate Media; sample pelletized Furnace Ramp rate: 5°C / min

[0265] Temperature: 725 °C

[0266] Dwell: 5 hours

[0267] Ambient gas: N2

[0268] By design, an excess of the carbon source (in this case, particulate carbon C65) was used to ensure that a composite material product was formed comprising the active material and the excess carbon.

[0269] Figure 1A shows the XRD data for the sample of Comparative example 1. From inspection it was detected that the sample was close to phase pure LiFePC.

[0270] Figure 1B shows the constant current data for the LiFePO4cathode active material of Comparative example 1. As shown in Figure 1B, 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 the LiFePO4) corresponded to a reversible material specific capacity of 107 mAh / g, indicating a reasonable lithium insertion / extraction cycle. The theoretical specific capacity for LiFePO4is approximately 170 mAh / g (assuming cycling of one lithium ion per LiFePO4formula 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.

[0271] Comparative Example 2 - LHP in the presence of iron (III) oxide and Iron Powder (no Carbon Source) - R1241

[0272] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, and iron metal (Hdganas AHC300)

[0273] Synthesis Stoichiometric Reaction: LiH2PO4+ 0.333 Fe2O3+ 0.333 Fe → LiFePO4+ H2OSynthesis Precursor Recipe:

[0274] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0275] 0.333 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.533 g

[0276] 0.333 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.18 g

[0277] Synthesis Conditions:

[0278] Mixing Conditions: MM 500 ball mill, 30 mins at a frequency of 30 Hz

[0279] Furnace Ramp rate: 5°C / min

[0280] Temperature: 725 °C

[0281] Dwell: 5 hours

[0282] Ambient gas: N2

[0283] Figure 2A shows the XRD data for Comparative example 2. From inspection, it was detected that the sample is close to phase pure LiFePO4.

[0284] Figure 2B shows the constant current data for the LiFePO4cathode active material of Comparative example 2. As shown in Figure 2B, during the charge process (lithium extraction from the LiFePO4) a charge equivalent to 5.7 mAh / g was obtained for the cathode active material. The subsequent discharge process (lithium re-insertion into the LiFePO4) corresponds to a reversible material specific capacity of 4.1 mAh / g, indicating a very poor lithium insertion / extraction cycle. The theoretical specific capacity for LiFePO4is 170 mAh / g (assuming cycling of one lithium ion per LiFePO4formula unit). This the 4.1 mAh / g corresponds to (4.1 / 170) x 100 % (i.e. an active material utilization of about 2 %). This represents a poor overall performance for this LiFePO4active material.

[0285] Comparative Example 3 - LHP in the presence of iron (III) oxide and Iron Powder (no Carbon Source) - R1115

[0286] Comparative example 2 was repeated with an alternative source of elemental iron.

[0287] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, and iron metal (Inoxia Limited)

[0288] Synthesis Stoichiometric Reaction: LiH2PO4+ 0.333 Fe2O3+ 0.333 Fe

[0289]

[0290] e → LiFePO4+ H2O

[0291] Synthesis Precursor Recipe:

[0292] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g0.333 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.533 g

[0293] 0.333 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.18 g

[0294] Synthesis Conditions’, as outlined above for Comparative example 2

[0295] Figure 3A shows the XRD data for Comparative example 3. From inspection, it was detected that the sample is close to phase pure LiFePC.

[0296] Figure 3B shows the constant current data for the LiFePC cathode active material of Comparative example 3. As shown in Figure 3B, during the charge process (lithium extraction from the LiFePC ) a charge equivalent to 3.3 mAh / g was obtained for the cathode active material. The subsequent discharge process (lithium re-insertion into the LiFePC ) corresponds to a reversible material specific capacity of 2.2 mAh / g, indicating a very poor lithium insertion / extraction cycle. The theoretical specific capacity for LiFePC is 170 mAh / g (assuming cycling of one lithium ion per LiFePC formula unit). This the 2.2 mAh / g corresponds to (2.2 / 170) x 100 % (i.e. an active material utilization of about 1 %). This represents a poor overall performance for this LiFePC active material.

[0297] Comparative Example 4 - lithium phosphate in the presence of iron (III) oxide and Iron Powder (no Carbon Source) - R1118

[0298] Mixture: Lithium phosphate, iron (III) oxide, and atomised iron metal (Inoxia Limited)

[0299] S

[0300]

[0301] ynthesis Stoichiometric Reaction: Li₃PO₄ + Fe + 2 FePO₄ → 3 LiFePO₄

[0302] Synthesis Precursor Recipe:

[0303] 1.000 equivalent Li₃PO₄ [RMM = 115.8 g / mol] (g): 1.158 g

[0304] 2.000 equivalent FePO₄ [RMM = 150.8 g / mol] (g): 3.016 g

[0305] 1 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.559 g

[0306] Synthesis Conditions: as outlined above for Comparative example 2

[0307] Figure 4 shows the XRD data for Comparative example 4. From inspection, it was detected that the sample is close to phase pure LiFePC.

[0308] Comparative Example 5 - LHP in the presence of iron (III) oxide and carbon (HMPE) (no elemental iron and / or Fe-P waste slag present) - R1769Comparative example 5 was prepared via the carbothermal reduction mechanism using 0 wt.% excess C.

[0309] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0310] Synthesis Stoichiometric Reaction: LiH₂PO₄ + 0.5 Fe₂O₃ + 0.5 C → LiFePO₄ + H₂O + 0.5 CO

[0311] Synthesis Precursor Recipe:

[0312] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0313] 0.5 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.7985 g

[0314] 0.5 mol C from HMPE [RMM = 12 g / mol] (where proportion of C in HMPE is 0.86) = 0.0698 g

[0315] Pellet mix 4.5 g: LiH2PO4= 2.4730 g, Fe2O3= 1.8998 g, HMPE = 0.1661 g

[0316] Synthesis Conditions:

[0317] Mixing Conditions: MM 500 ball mill, 30 mins at a frequency of 30 Hz

[0318] Furnace Ramp rate: 5°C / min

[0319] Temperature: 725°C

[0320] Dwell: 5 hours

[0321] Ambient gas: N2

[0322] Figure 5A shows the XRD data for Comparative example 5 (ID: R1769). From inspection, it was detected that the sample is close to phase pure LiFePC, with the addition of low-level impurities.

[0323] Figure 5B shows the constant current data for the LiFePC cathode active material for Comparative example 5. As shown in Figure 5B, the second cycle discharge process (lithium re-insertion into the LiFePC ) corresponds to a reversible material specific capacity of 97 mAh / g. The theoretical specific capacity for LiFePC is 170 mAh / g (assuming cycling of one lithium ion per LiFePC formula unit). Thus the 97 mAh / g corresponds to (97 / 170) x 100 % (i.e. an active material utilization of about 57%).

[0324] Comparative Example 6 - LHP in the presence of iron (III) oxide and carbon (HMPE) (no elemental iron and / or Fe-P waste slag present) - R1513Comparative example 6 was prepared via the carbothermal reduction mechanism using 1.58 wt% excess C.

[0325] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0326] Synthesis Stoichiometric Reaction: LiH₂PO₄ + 0.5 Fe₂O₃ + 0.75 C

[0327]

[0328] LiFePO₄ + H₂O + 0.5 CO Where C is in 50% molar excess (1.58 wt.% excess)

[0329] Synthesis Precursor Recipe:

[0330] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0331] 0.5 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.7985 g

[0332] 0.75 mol C from HMPE [RMM = 12 g / mol] (where proportion of C in HMPE is 0.86) = 0.1047 g

[0333] Pellet mix 4.5 g: LiH2PO4= 2.4791 g, Fe2O3= 1.9011 g, HMPE = 0.2491 g

[0334] Synthesis Conditions: as outlined above for Comparative example 5

[0335] Figure 6A shows the XRD data for Comparative example 6 (ID: R1513). From inspection, it was detected that the sample is close to phase pure LiFePC, with the addition of low-level impurities.

[0336] Figure 6B shows the constant current data for the LiFePC cathode active material for Comparative example 6. As shown in Figure 6B, the second cycle discharge process (lithium re-insertion into the LiFePC ) corresponds to a reversible material specific capacity of 161 mAh / g. The theoretical specific capacity for LiFePC is 170 mAh / g (assuming cycling of one lithium ion per LiFePC formula unit). Thus the 161 mAh / g corresponds to (161 / 170) x 100 % (i.e. an active material utilization of about 95%).

[0337] Comparative Example 7 - LHP in the presence of iron (III) oxide and carbon (HMPE) (no elemental iron and / or Fe-P waste slag present) - R1511

[0338] Comparative example 7 was prepared via the carbothermal reduction mechanism using 3.16 wt.% excess C.Mixture: Lithium dihydrogen phosphate, iron (III) oxide, and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0339] Synthesis Stoichiometric Reaction: LiH₂PO₄ + 0.5 Fe₂O₃ + 1 C → LiFePO₄ + H₂O + 0.5 CO Where C is in 100% molar excess (3.16 wt.% excess)

[0340] Synthesis Precursor Recipe:

[0341] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0342] 0.5 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.7985 g

[0343] 1 mol C from HMPE [RMM = 12 g / mol] (where proportion of C in HMPE is 0.86) = 0.1395 g

[0344] Pellet mix 4.5 g: LiH2PO4= 2.4737 g, Fe2O3= 1.9004 g, HMPE = 0.0.3323 g

[0345] Synthesis Conditions: as outlined above for Comparative example 5

[0346] Figure 7A shows the XRD data for Comparative example 7 (ID: R1511). From inspection, it was detected that the sample is close to phase pure LiFePC, with the addition of low-level impurities.

[0347] Figure 7B shows the constant current data for the LiFePC cathode active material for Comparative example 7. As shown in Figure 7B, the second cycle discharge process (lithium re-insertion into the LiFePC ) corresponds to a reversible material specific capacity of 150 mAh / g. The theoretical specific capacity for LiFePC is 170 mAh / g (assuming cycling of one lithium ion per LiFePC formula unit). Thus the 150 mAh / g corresponds to (150 / 170) x 100 % (i.e. an active material utilization of about 88%).

[0348] Example 1 - LHP in the presence of iron (III) oxide, elemental iron and carbon (HMPE) -R1254

[0349] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, iron metal (Hdganas AHC300), and high modulus polyethylene powder (HMPE) (HMPE35A, Goonvean Fibres Ltd)

[0350] Synthesis Stoichiometric Reaction: LiH₂PO₄ + 0.4 Fe₂O₃ + 0.2 Fe + 0.2 C → LiFePO₄ + H₂O + 0.2 CO

[0351] Synthesis Precursor Recipe:1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0352] 0.4 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.639 g

[0353] 0.2 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.112 g

[0354] 0.2 mol Carbon from HMPE [RMM = 12 g / mol] (where the proportion of C in HMPE is 0.86) = 0.0279 g

[0355] Pellet mix 4.5 g: LiH2PO4= 2.572 g, Fe2O3= 1.582 g, Fe = 0.277 g, HMPE = 0.069 g

[0356] Synthesis Conditions’, as outlined above for Comparative example 2

[0357] Example 1 was repeated three times, and is reported below as Examples 1a, 1b and 1c.

[0358] Figure 8A shows the XRD data for Examples 1a (R1254), 1b (R1691) and 1c (R1707). From inspection, it was detected that the sample is close to phase pure LiFePC.

[0359] Figure 8B shows the constant current data for the LiFePC cathode active material for Example 1a. As shown in Figure 11 B, the discharge process (lithium re-insertion into the LiFePC ) corresponds to a reversible material specific capacity of 132 mAh / g, indicating a good lithium insertion / extraction cycle. The theoretical specific capacity for LiFePC is 170 mAh / g (assuming cycling of one lithium ion per LiFePC formula unit). Thus the 132 mAh / g corresponds to (132 / 170) x 100 % (i.e. an active material utilization of about 77 %). This represents a good overall performance for this LiFePC active material.

[0360] However, the reproducibility proved unsatisfactory, with discharge capacities on the second cycle of 85 mAh / g (Example 1b) and 125 mAh / g (Example 1c) obtained. Given the theoretical specific capacity for LiFePC is 170 mAh / g, these values correspond to active material utilisations of 50% and 74%).

[0361] Example 2 - LHP in the presence of iron (III) oxide, elemental iron and carbon (coal-tar pitch) - R1243

[0362] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, iron metal (Hdganas AHC300), and coal tar pitch (CTP)

[0363] Synthesis Stoichiometric Reaction: LiH₂PO₄ + 0.4 Fe₂O₃ + 0.2 Fe + 0.26 C

[0364]

[0365] LiFePCU + H2O + 0.2 CO

[0366] Synthesis Precursor Recipe:1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0367] 0.4 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.639 g

[0368] 0.2 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.112 g

[0369] 0.26 mol Carbon CTP [RMM = 12 g / mol] (30% molar C excess) = 0.0312 g Pellet mix 4.5 g: LiH2PO4= 2.581 g, Fe2O3= 1.588 g, Fe = 0.278 g, CTP = 0.0775 g

[0370] Synthesis Conditions’, as outlined above for Comparative example 2

[0371] Figure 9A shows the XRD data for Example 2. From inspection, it was detected that the sample is close to phase pure LiFePCU.

[0372] Figure 9B shows the constant current data for the LiFePCU cathode active material. As shown in Figure 9B, during the charge process (lithium extraction from the LiFePCU) a charge equivalent to 117 mAh / g was obtained for the cathode active material. The subsequent discharge process (lithium re-insertion into the LiFePCU) corresponds to a reversible material specific capacity of 116 mAh / g, indicating a good lithium insertion / extraction cycle. The theoretical specific capacity for LiFePCU is 170 mAh / g (assuming cycling of one lithium ion per LiFePC formula unit). Thus the 116 mAh / g corresponds to (116 / 170) x 100 % (i.e. an active material utilization of about 68 %). This represents good overall performance for this LiFePC active material.

[0373] Example 3 - LHP in the presence of iron (III) oxide, elemental iron and carbon (particulate) - R1116

[0374] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, atomised iron metal (Inoxia Limited), and particulate carbon (Enasco carbon, Imerys)

[0375] Synthesis Stoichiometric Reaction: LiH₂PO₄ + (1.25 x 0.333) Fe₂O₃ + (0.75 x 0.333) Fe + xC

[0376]

[0377] LiFePO₄ + H₂O + 0.25CO | LiH₂PO₄ + 0.417Fe₂O₃ + 0.242Fe + 0.499C → LiFePO₄ + H₂O + 0.25CO

[0378] Synthesis Precursor Recipe:

[0379] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0380] 1.25 x 0.333 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.666 g

[0381] 0.75 x 0.333 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.139 g

[0382] 0.5 mol Carbon ENSACO 250 G [RMM = 12 g / mol] = 0.06 g (where Cmoiexcess is 100%)Pellet mix 4.5 g: LiH₂PO₄ = 2.4607 g, Fe₂O₃ = 1.577 g, Fe = 0.320 g, Ensaco 250G = 0.142 g

[0383] Synthesis Conditions’, as outlined above for Comparative example 2

[0384] Figure 10 shows the XRD data for Example 3. From inspection, it was detected that the sample is close to phase pure LiFePC.

[0385] Example 4 - LHP in the presence of iron (III) oxide, elemental iron and carbon (HMPE) - R1117

[0386] Examples 1 and 2 (prepared with 100% molar excess carbon following the ferrothermal reaction equation above) were repeated with a different balance of elemental iron, iron oxide and carbon.

[0387] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, atomised iron metal (Inoxia Limited), and high modulus polyethylene powder (HMPE) (HMPE35A, Goonvean Fibres Ltd)

[0388] Synthesis Stoichiometric Reaction: LiH₂PO₄ + (1.25 x 0.333) Fe₂O₃ + (0.75 x 0.333) Fe + xC

[0389]

[0390] LiFePO4+ H2O + 0.25CO

[0391] Synthesis Precursor Recipe:

[0392] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0393] 1.25 x 0.333 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.666 g

[0394] 0.75 x 0.333 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.139 g

[0395] 0.5 mol Carbon [RMM = 12 g / mol] as HMPE = 0.07 g (where Cmolexcess is 100%) Pellet mix 4.5 g: LiH2PO4= 2.448 g, Fe2O3= 1.569 g, Fe = 0.318 g, HMPE = 0.165 g

[0396] Synthesis Conditions: as outlined above for Comparative example 2

[0397] Figure 11 A shows the XRD data for Example 4. From inspection, it was detected that the sample is close to phase pure LiFePO4.

[0398] Figure 11 B shows the constant current data for the LiFePO4 cathode active material. As shown in Figure 11 B, during the charge process (lithium extraction from the LiFePO4) a charge equivalent to 138 mAh / g was obtained for the cathode active material. The subsequent discharge process (lithium re-insertion into the LiFePO4) corresponds to a reversible materialspecific capacity of 136 mAh / g, indicating a good lithium insertion / extraction cycle. The theoretical specific capacity for LiFePCU is 170 mAh / g (assuming cycling of one lithium ion per LiFePC formula unit). Thus the 136 mAh / g corresponds to (136 / 170) x 100 % (i.e. an active material utilization of about 80 %). This represents good overall performance for this LiFePC active material.

[0399] Example 5 - LHP in the presence of iron (III) oxide, elemental iron and carbon (blend of HMPE and mwCNT) - R1270

[0400] Example 1 was repeated but with 0.13 mol HMPE and 0.13 mol multi-walled carbon nanotubes, as opposed to 0.26 mol HMPE.

[0401] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, iron metal (Hdganas AHC300), high modulus polyethylene powder (HMPE) (HMPE35A, Goonvean Fibres Ltd), and Multi-Walled Carbon Nanotubes (NC7000)

[0402] Synthesis Stoichiometric Reaction: LiH₂PO₄ + 0.4 Fe₂O₃ + 0.2 Fe + 0.26 C

[0403]

[0404] LiFePCU + H2O + 0.2 CO

[0405] Synthesis Precursor Recipe:

[0406] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0407] 0.4 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.639 g

[0408] 0.2 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.112 g

[0409] 0.26 mol carbon where Cmolexcess is 30%, of which:

[0410] - 0.13 mol Carbon NC7000 [RMM = 12 g / mol] = 0.0156g

[0411] - 0.13 mol Carbon HMPE [RMM = 12 g / mol] (proportion of C in HMPE is 0.86) = 0.0182 g

[0412] Pellet mix 4.5 g: LiH2PO4= 2.564 g, Fe2O3= 1.577 g, Fe = 0.276 g, HMPE = 0.0450 g, NC7000 = 0.0385

[0413] Synthesis Conditions: as outlined above for Comparative example 2

[0414] Figure 12 shows the constant current data for the LiFePCU cathode active material. As shown in Figure 12, during the charge process (lithium extraction from the LiFePCU) a charge equivalent to 132 mAh / g was obtained for the cathode active material. The subsequent discharge process (lithium re-insertion into the LiFePCU) corresponds to a reversible material specific capacity of 132 mAh / g, indicating a good lithium insertion / extraction cycle. Thetheoretical specific capacity for LiFePCU is 170 mAh / g (assuming cycling of one lithium ion per LiFePCU formula unit). Thus the 136 mAh / g corresponds to (132 / 170) x 100 % (i.e. an active material utilization of about 78 %). This represents good overall performance for this LiFePC active material.

[0415] Example 6 - Lithium phosphate in the presence of iron (III) phosphate, elemental iron and carbon (petroleum pitch) - R1280

[0416] Comparative example 4 was repeated with the addition of carbon.

[0417] Mixture: Lithium phosphate, iron (III) phosphate, iron metal (Hbganas AHC300), and petroleum pitch (LIONCOAT, RAIN Carbon)

[0418] Synthesis Stoichiometric Reaction: Li₃PO₄ + Fe + 2 FePO₄ + C → 3 LiFePO₄ + C

[0419] Synthesis Precursor Recipe:

[0420] 1.000 equivalent Li₃PO₄ [RMM = 115.8 g / mol] (g): 1.158 g

[0421] 2.000 equivalent FePO4 [RMM = 150.8 g / mol] (g): 3.016 g

[0422] 1.000 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.559 g

[0423] 1.000 equivalent Carbon (Lioncoat LM) [atomic mass = 12 g / mol] (g) = 0.12 g Pellet mix: Li₃PO₄ = 1.0737g, FePO₄ = 2.7966 g, Fe = 0.5183g, Lioncoat LM = 0.111g

[0424] Synthesis Conditions: as outlined above for Comparative example 2

[0425] Figure 13A shows the XRD data for Example 6. From inspection, it was detected that the sample is close to phase pure LiFePC.

[0426] Figure 13B shows the constant current data for the LiFePCU cathode active material. As shown in Figure 13B, during the charge process (lithium extraction from the LiFePCU) a charge equivalent to 114 mAh / g was obtained for the cathode active material. The subsequent discharge process (lithium re-insertion into the LiFePCU) corresponds to a reversible material specific capacity of 111 mAh / g, indicating a reasonable lithium insertion / extraction cycle. The theoretical specific capacity for LiFePCU is 111 mAh / g (assuming cycling of one lithium ion per LiFePCU formula unit). Thus the 111 mAh / g corresponds to (111 / 170) x 100 % (i.e. an active material utilization of about 65 %). This represents a reasonable overall performance for this LiFePCU active material.Example 7 - LHP in the presence of iron (III) oxide, elemental iron, manganese carbonate and carbon (petroleum pitch) - M 1025

[0427] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, atomised iron metal (Hoganas AHC300), manganese(ll) carbonate, and petroleum pitch (LIONCOAT, RAIN Carbon)

[0428] Synthesis Stoichiometric Reaction: LiH₂PO₄ + 0.2 Fe₂O₃ + 0.1 Fe + 0.50 M

[0429]

[0430] nCO₃ + 0.1 C → LiFe₀.₅Mn₀.₅PO₄ + H₂O + 0.5 CO₂ + 0.1 CO

[0431] Synthesis Precursor Recipe:

[0432] 0.01 ml LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g (Sigma)

[0433] 0.002 mol Fe₂O₃ [RMM = 159.7 g / mol] (g): 0.31992 g (Lanxess)

[0434] 0.001 mol Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.05585 g (Hoganas AHC300 Fe Powder)

[0435] 0.005 mol MnCO3[RMM = 88.95 g / mol] (g): 0.5748 g (Arxo)

[0436] 0.001 mol Carbon [RMM = 12 g / mol] (% mass excess = 75% -> 0.00175 mol) Lioncoat LM (100 wt% carbon) = 0.00175 x 12 = 0.0470 g

[0437] Pellet mix 4.5 g: LiH₂PO₄ = 2.3258 g, Fe₂O₃ = 0.7159 g, MnCO₃ = 1.2862 g, Lioncoat petroleum pitch = 0.047 g

[0438] Synthesis Conditions:

[0439] Mixing Conditions: MM 500 ball mill, 30 mins at a frequency of 30 Hz

[0440] Furnace Ramp rate: 5°C / min

[0441] Temperature: 675 °C

[0442] Dwell: 5 hours

[0443] Ambient gas: N2

[0444] Figure 14 shows the XRD data for Example 7. From inspection, it was detected that the sample is close to phase pure LiFeMnPC, with the addition of low-level impurities.

[0445] Example 8 - LHP in the presence of iron (III) oxide, elemental iron, manganese carbonate and carbon (petroleum pitch) - M 1026

[0446] Example 7 was repeated with different stoichiometries.

[0447] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, atomised iron metal (Hoganas AHC300), manganese(ll) carbonate, and petroleum pitch (LIONCOAT, RAIN Carbon)Synthesis Stoichiometric Reaction: UH2PO4 + 0.1667 Fe2O3+ 0.1667 Fe + 0.50 MnCO3+ x C

[0448]

[0449] LiFe₀.₅Mn₀.₅PO₄ + H₂O + 0.5 CO₂ + x CO

[0450] Synthesis Precursor Recipe:

[0451] 0.01 ml LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g (Sigma)

[0452] 0.0016667 mol Fe2O3[RMM = 159.7 g / mol] (g): 0.2666 g (Lanxess)

[0453] 0.0016667 mol Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.09308 g (Hoganas AHC300 Fe Powder)

[0454] 0.005 mol MnCO3[RMM = 88.95 g / mol] (g): 0.5748 g (Arxo)

[0455] x mol Carbon [RMM = 12 g / mol] (% mass excess = 75% equivalent. -> 0.001875 mol) Lioncoat LM (100 wt% carbon) = 0.001875 x 12 = 0.0225 g

[0456] Pellet mix 4.5 g: UH2PO4 = 2.3428 g, Fe2O3= 0.6010 g, Fe powder = 0.2098 g, MnCO3= 1.2956 g, Lioncoat petroleum pitch = 0.0507 g

[0457] Synthesis Conditions: as outlined above for Example 7

[0458] Figure 15 shows the XRD data for Example 8. From inspection, it was detected that the sample is close to phase pure LiFeMnPC, with the addition of low-level impurities.

[0459] Example 9 - LHP in the presence of iron (III) oxide, elemental iron, manganese hydroxide and carbon (HMPE) - M1027

[0460] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, atomised iron metal (Hoganas AHC300), manganese (II) hydroxide, and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0461] Synthesis Stoichiometric Reaction: UH2PO4 + 0.2 Fe2O3+ 0.1 Fe + 0.50 M

[0462]

[0463] n(OH)2 + 0.1 C LiFe₀.₅Mn₀.₅PO₄ + 2H₂O + 0.5 CO₂ + 0.1 CO

[0464] Synthesis Precursor Recipe:

[0465] 0.01 ml LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g (Sigma)

[0466] 0.002 mol Fe2O3[RMM = 159.7 g / mol] (g): 0.31992 g (Lanxess)

[0467] 0001 mol Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.5585 g (Hoganas AHC300 Fe Powder)

[0468] 0.005 mol Mn(OH)2[RMM = 88.95 g / mol] (g): 0.4448 g (Arxo)0.001 mol Carbon [RMM = 12 g / mol] (% mass excess = 75% -> 0.00175 mol) HMPE (86 wt% carbon) = 0.00175 x (12 / 0.86) = 0.0244 g

[0469] Pellet mix 4.5 g: LiH2PO4= 2.4821 g, Fe2O3= 0.7640 g, Fe Metal = 0.1334 g, Mn(OH)2= 1.0657 g, HMPE = 0.0583 g

[0470] Synthesis Conditions’, as outlined above for Example 7

[0471] Figure 16 shows the XRD data for Example 9 (ID: M1027). From inspection, it was detected that the sample is close to phase pure LiFeMnPO₄, with the addition of low-level impurities.

[0472] Example 10 - LHP in the presence of iron (III) oxide, elemental iron, manganese oxide and carbon (HMPE) - M 1059

[0473] Example 9 was repeated using manganese oxide as opposed to manganese (II) hydroxide.

[0474] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, atomised iron metal (Höganäs AHC300), manganese (III) oxide, and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0475] Synthesis Stoichiometric Reaction: LiH2PO4+ 0.2 Fe2O3+ 0.1 Fe + 0.25 M

[0476]

[0477] n2O3+ 0.35 C LiFe₀.₅Mn₀.₅PO₄ + H₂O + 0.35 CO

[0478] Synthesis Precursor Recipe:

[0479] 0.01 ml LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g (Sigma)

[0480] 0.002 mol Fe2O3[RMM = 159.7 g / mol] (g): 0.31992 g (Lanxess)

[0481] 0001 mol Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.5585 g

[0482] 0.005 mol Mn2O3[RMM = 88.95 g / mol] (g): 0.3947 g (Sigma)

[0483] 0.0035 mol Carbon [RMM = 12 g / mol] HMPE (86 wt% carbon) = 0.0035 x (12 / 0.86) = 0.0488 g

[0484] Pellet mix 4.5 g: LiH2PO4= 2.5163 g, Fe2O3= 0.7746 g, Fe Metal = 0.1352 g, Mn2O3= 0.9556 g, HMPE = 0.1182 g

[0485] Synthesis Conditions: as outlined above for Example 7

[0486] Figure 17 shows the XRD data for Example 10 (ID: M1059). From inspection, it was detected that the sample is close to phase pure LiFeMnPC, with the addition of low-level impurities.Example 11 - LHP in the presence of iron (III) oxide, elemental iron, and carbon (petroleum pitch) - R1266

[0487] Example 11 was prepared via the ferrothermal reduction mechanism using 0 wt.% excess C from a petroleum pitch source.

[0488] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, iron metal (Hoganas AHC300), and petroleum pitch (LIONCOAT, RAIN Carbon)

[0489] Synthesis Stoichiometric Reaction: LiH₂PO₄ + 0.4 Fe₂O₃ + 0.2 Fe + 0.2 C → LiFePO₄ + H₂O + 0.2 CO

[0490] Synthesis Precursor Recipe:

[0491] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0492] 0.4 equivalent Fe2Os [RMM = 159.7 g / mol] (g): 0.639 g

[0493] 0.2 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.112 g

[0494] 0.2 mol Lioncoat petroleum pitch [RMM = 12 g / mol] = 0.0279 g

[0495] Pellet mix 4.5 g: LiH₂PO₄ = 2.5770 g, Fe₂O₃ = 1.5850 g, Fe = 0.2780 g, Lioncoat = 0.0595 g

[0496] Synthesis Conditions:

[0497] Mixing Conditions: MM 500 ball mill, 30 mins at a frequency of 30 Hz

[0498] Furnace Ramp rate: 5°C / min

[0499] Temperature: 725°C

[0500] Dwell: 5 hours

[0501] Ambient gas: N2

[0502] Figure 18A shows the XRD data for Example 11 (ID: R1266). From inspection, it was detected that the sample is close to phase pure LiFePO₄, with the addition of low-level impurities.Figure 18B shows the constant current data for the LiFePO₄ cathode active material for Example 12. As shown in Figure 18B, the second cycle discharge process (lithium re-insertion into the LiFePC ) corresponds to a reversible material specific capacity of 62 mAh / g. The theoretical specific capacity for LiFePC is 170 mAh / g (assuming cycling of one lithium ion perLiFePO₄ formula unit). Thus the 62 mAh / g corresponds to (62 / 170) x 100 % (i.e. an active material utilization of about 41 %).

[0503] Example 12 - LHP in the presence of iron (III) oxide, elemental iron, and carbon (HMPE) - R1773

[0504] Example 12 was prepared via the ferrothermal reduction mechanism using 1.58 wt.% excess C from a polymer source.

[0505] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, iron metal (Hdganas AHC300), and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0506] Synthesis Stoichiometric Reaction: UH2PO4 + 0.4 Fe2O3+ 0.2 Fe + 0.4386 C

[0507]

[0508] LiFePCU + H2O + 0.2 CO

[0509] Synthesis Precursor Recipe:

[0510] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0511] 0.4 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.6388 g

[0512] 0.2 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.1117 g

[0513] 0.4386 mol C from HMPE [RMM = 12 g / mol] (where proportion of C in HMPE is 0.86) = 0.0612 g

[0514] Pellet mix 5.5 g: LiH2PO4= 3.0914 g, Fe2O3= 1.9000 g, Fe = 0.3332 g, HMPE = 0.1822 g

[0515] Synthesis Conditions: as outlined above for Example 11

[0516] Figure 19A shows the XRD data for Example 12 (ID: R1773). From inspection, it was detected that the sample is close to phase pure LiFePO₄, with the addition of low-level impurities.Figure 19B shows the constant current data for the LiFePO₄ cathode active material for Example 13. As shown in Figure 19B, the second cycle discharge process (lithium re-insertion into the LiFePO₄) corresponds to a reversible material specific capacity of 131 mAh / g. The theoretical specific capacity for LiFePO₄ is 170 mAh / g (assuming cycling of one lithium ion per LiFePO₄ formula unit). Thus the 131 mAh / g corresponds to (131 / 170) x 100 % (i.e. an active material utilization of about 77 %). This represents a good overall performance for this LiFePO₄ active material.Example 13 - LHP in the presence of iron (III) oxide, elemental iron and carbon (HMPE) - R1787

[0517] Example 13 was prepared via the ferrothermal reduction mechanism using 3.16 wt.% excess C from a polymer source.

[0518] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, iron metal (Hoganas AHC300), and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0519] Synthesis Stoichiometric Reaction: LiH₂PO₄ + 0.4 Fe₂O₃ + 0.2 Fe + 0.6769 C

[0520]

[0521] LiFePCU + H2O + 0.2 CO

[0522] Synthesis Precursor Recipe:

[0523] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0524] 0.4 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.6388 g

[0525] 0.2 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.1117 g

[0526] 0.4386 mol C from HMPE [RMM = 12 g / mol] (where proportion of C in HMPE is 0.86) = 0.0612 g

[0527] Pellet mix 5.5 g: LiH2PO4= 3.0914 g, Fe2O3= 1.9000 g, Fe = 0.3332 g, HMPE = 0.2812 g

[0528] Synthesis Conditions: as outlined above for Example 11

[0529] Figure 20A shows the XRD data for Example 13 (ID: R1787). From inspection, it was detected that the sample is close to phase pure LiFePO₄, with the addition of low-level impurities.Figure 20B shows the constant current data for the LiFePO₄ cathode active material for Example 13. As shown in Figure 20B, the second cycle discharge process (lithium re-insertion into the LiFePO₄) corresponds to a reversible material specific capacity of 136 mAh / g. The theoretical specific capacity for LiFePO₄ is 170 mAh / g (assuming cycling of one lithium ion per LiFePO₄ formula unit). Thus the 136 mAh / g corresponds to (136 / 170) x 100 % (i.e. an active material utilization of about 80 %). This represents a good overall performance for this LiFePO₄ active material.

[0530] Example 14 - LHP in the presence of iron (III) oxide, elemental iron, and carbon (HMPE)Samples of example 14 were prepared via the blended carbothermal-ferrothermal reduction mechanism (outlined in “Blended reaction pathways and CT: FT ratio”) using 0 wt.% excess C.

[0531] Mixture: Lithium dihydrogen phosphate, elemental iron, iron (III) oxide, and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0532] Synthesis Stoichiometric Reaction: LiH₂PO₄ + XFe₂O₃ + YFe + ZC → LiFePO₄ + H₂O + N CO

[0533] Synthesis Precursor Recipe:

[0534] Synthesis CT% Mol LiH₂PO₄ Mol. Fe₂O₃ Mol. Fe Mol. C no. (X) (Y) (Z) R1691 0 (FT) 1.0000 0.4000 0.2000 0.2001 R1692 10 1.0000 0.4082 0.1837 0.2245 R1693 20 1.0000 0.4166 0.1667 0.2500 R1694 30 1.0000 0.4255 0.1490 0.2766 R1770 40 1.0000 0.4348 0.1305 0.3046 R1695 50 1.0000 0.4444 0.1112 0.3333 R1771 70 1.0000 0.4651 0.0699 0.3953 R1772 90 1.0000 0.4878 0.0243 0.4627

[0535]

[0536] Pellet mix masses:

[0537] Synthesis CT% Mass Mass Fe2O3 Mass Fe [g] Mass C no. UH2PO4 [g] [g] (HMPE) [g] R1691 0 (FT) 3.0914 1.9000 0.3323 0.0831 R1692 10 3.0296 1.9000 0.2991 0.0914 R1693 20 2.9680 1.9000 0.2658 0.0997 R1694 30 2.9059 1.9000 0.2326 0.1080 R1770 40 2.8442 1.9001 0.1995 0.1164 R1695 50 2.7823 1.9000 0.1662 0.1246 R1771 70 2.6585 1.9000 0.0998 0.1412 R1772 90 2.5348 1.9000 0.0331 0.1576

[0538]

[0539] Synthesis Conditions: as outlined above for Example 11Figure 21A shows the XRD data for Example 14. From inspection, it was detected that the sample is close to phase pure LiFePO₄, with the addition of low-level impurities.Figures 21B and 21C show the constant current data for the LiFePO₄ cathode active material for Example 14. As shown in Figures 21B and 21C, the second cycle discharge process (lithium re-insertion into the LiFePO₄) corresponds to a reversible material specific capacity of 85 mAh / g, 113 mAh / g, 115 mAh / g, 122 mAh / g, 130 mAh / g, 138 mAh / g, 137 mAh / g, 134 mAh / g at respective CT-FT blend proportions of FT, 10%, 20%, 30%, 40%, 50%, 70%, 90%. The theoretical specific capacity for LiFePO₄ is 170 mAh / g (assuming cycling of one lithium ion per LiFePO₄ formula unit). Thus, the peak reversible material specific capacity in the series of 138 mAh / g at 50% CT reaction blend corresponds to (138 / 170) x 100 % (i.e. an active material utilization of about 81 %). This shows an improvement over 0.00 wt.% C excess 100% CT Comparative example 5 (R1769), which had an active material utilization of 57%.

[0540] Example 15 - LHP in the presence of elemental iron, iron (III) oxide and carbon (HMPE)

[0541] Samples of example 15 were prepared via the blended carbothermal-ferrothermal reduction mechanism (outlined in “Blended reaction pathways and CT: FT ratio”) using 1.58 wt.% excess C.

[0542] Mixture: Lithium dihydrogen phosphate, elemental iron, iron (III) oxide, and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0543] Synthesis Stoichiometric Reaction: LiH₂PO₄ + XFe₂O₃ + YFe + ZC → LiFePO₄ + H₂O + N CO

[0544] Synthesis Precursor Recipe:

[0545] Synthesis CT% Mol LiH₂PO₄ Mol. Fe₂O₃ Mol. Fe Mol. C no. (X) (Y) (Z) R1773 0 (FT) 1.0000 0.4000 0.2006 0.4386 R1774 10 1.0000 0.4082 0.1838 0.4645 R1775 30 1.0000 0.4255 0.1489 0.5173 R1776 50 1.0000 0.4442 0.1112 0.5767 R1777 70 1.0000 0.4651 0.0697 0.6405 R1778 90 1.0000 0.4878 0.0244 0.7116

[0546]

[0547] Pellet mix masses:

[0548] Synthesis CT% Mass Mass Fe₂O₃ Mass Fe [g] Mass C no. LiH₂PO₄ [g] [g] (HMPE) [g] R1773 0 (FT) 3.0914 1.9000 0.3332 0.1822 R1774 10 3.0296 1.9000 0.2992 0.1891 R1775 30 2.9060 1.9000 0.2325 0.2020 R1776 50 2.7822 1.8990 0.1662 0.2156 R1777 70 2.6586 1.9001 0.0996 0.2288 R1778 90 2.5350 1.9000 0.0332 0.2424

[0549]

[0550] Synthesis Conditions: as outlined above for Example 11

[0551] Figure 22A shows the XRD data for Example 15. From inspection, it was detected that the sample is close to phase pure LiFePO₄, with the addition of low-level impurities.Figures 22B and 22C show the constant current data for the LiFePO₄ cathode active material for Example 15. As shown in Figures 22B and 22C, the second cycle discharge process (lithium re-insertion into the LiFePO₄) corresponds to a reversible material specific capacity of 131 mAh / g, 130 mAh / g, 132 mAh / g, 128 mAh / g, 135 mAh / g, 130 mAh / g at respective CT-FT blend proportions of FT, 10%, 30%, 50%, 70%, 90%. The theoretical specific capacity for LiFePO₄ is 170 mAh / g (assuming cycling of one lithium ion per LiFePO₄ formula unit). Thus, the peak reversible material specific capacity in the blend reaction sample series is 135 mAh / g at 70% CT reaction blend corresponds to (135 / 170) x 100 % (i.e. an active material utilization of about 79%). This shows a decrease in specific capacity versus 1.58 wt.% C excess 100% CT Comparative example 6 (R1513), which had an active material utilization of 95%.

[0552] Example 16 - LHP in the presence of iron (III) oxide, elemental iron, and carbon (HMPE)

[0553] Samples of example 16 were prepared via the blended carbothermal-ferrothermal reduction mechanism (outlined in “Blended reaction pathways and CT: FT ratio”) using 3.16 wt.% excess C.

[0554] Mixture: Lithium dihydrogen phosphate, elemental iron, iron (III) oxide, and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0555] Synthesis Stoichiometric Reaction: LiH₂PO₄ + X Fe₂O₃ + Y Fe + Z C → LiFePO₄ + H₂O + NCOSynthesis Precursor Recipe:

[0556] Synthesis CT% Mol LiH₂PO₄ Mol. Fe₂O₃ Mol. Fe Mol. C no. (X) (Y) (Z) R1787 0 (FT) 1.0000 0.4000 0.2000 0.6769 R1779 10 1.0000 0.4081 0.1837 0.7033 R1780 30 1.0000 0.4255 0.1490 0.7593 R1781 50 1.0000 0.4444 0.1112 0.8198 R1782 70 1.0000 0.4652 0.0698 0.8868 R1783 90 1.0000 0.4878 0.0244 0.9594

[0557]

[0558] Pellet mix masses:

[0559] Synthesis CT% Mass Mass Fe₂O₃ Mass Fe [g] Mass C no. LiH₂PO₄ [g] [g] (HMPE) [g] R1787 0 (FT) 3.0914 1.9000 0.3323 0.2812 R1779 10 3.0296 1.8999 0.2991 0.2863 R1780 30 2.9059 1.8999 0.2326 0.2965 R1781 50 2.7824 1.9001 0.1663 0.3065 R1782 70 2.6585 1.9001 0.0997 0.3168 R1783 90 2.5350 1.8999 0.0333 0.3268

[0560]

[0561] Synthesis Conditions: as outlined above for Example 12

[0562] Figure 23A shows the XRD data for Example 16. From inspection, it was detected that the sample is close to phase pure LiFePO₄, with the addition of low-level impurities.Figures 23B and 23C show the constant current data for the LiFePO₄ cathode active material for Example 16. As shown in Figures 23B and 23C, the second cycle discharge process (lithium re-insertion into the LiFePO₄) corresponds to a reversible material specific capacity of 135 mAh / g, 126 mAh / g, 124 mAh / g, 129 mAh / g, 119 mAh / g, 132 mAh / g at respective CT-FT blend proportions of FT, 10%, 30%, 50%, 70%, 90%. The theoretical specific capacity for LiFePO₄ is 170 mAh / g (assuming cycling of one lithium ion per LiFePO₄ formula unit). Thus, the peak reversible material specific capacity of the blend reaction sample series is 132 mAh / g at 90% CT reaction blend corresponds to (132 / 170) x 100 % (i.e. an active material utilization of about 78%). This shows a decrease in specific capacity versus 3.16 wt.% C excess 100% CT Comparative example 7 (R1511), which had an active material utilization of 88%.Example 17 - LHP in the presence of iron (III) oxide, elemental iron, and carbon (HMPE) - R1695

[0563] Example 17 was prepared via the blended reaction mechanism at a ratio 50:50 using 0 wt.% excess C.

[0564] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, iron metal (Hoganas AHC300), and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0565] Synthesis Stoichiometric Reaction: LiH₂PO₄ + 0.4444 Fe₂O₃ + 0.1112 Fe + 0.3333

[0566]

[0567] C LiFePO4+ H2O + 0.3333 CO

[0568] Synthesis Precursor Recipe:

[0569] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0570] 0.4444 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.7097 g

[0571] 0.1112 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.0621 g

[0572] 0.3333 mol C from HMPE [RMM = 12 g / mol] (where proportion of C in HMPE is 0.86) = 0.0465 g

[0573] Pellet mix 5.5 g: LiH2PO4= 2.7823 g, Fe2O3= 1.9000 g, Fe = 0.1662 g, HMPE = 0.1246 g

[0574] Synthesis Conditions: as outlined above for Example 11

[0575] Figure 24A shows the XRD data for Example 17 (ID: R1695). From inspection, it was detected that the sample is close to phase pure LiFePO₄, with the addition of low-level impurities.Figure 24B shows the constant current data for the LiFePO₄ cathode active material for Example 17. As shown in Figure 24B, the second cycle discharge process (lithium re-insertion into the LiFePO₄) corresponds to a reversible material specific capacity of 138 mAh / g. The theoretical specific capacity for LiFePO₄ is 170 mAh / g (assuming cycling of one lithium ion per LiFePO₄ formula unit). Thus the 138 mAh / g corresponds to (138 / 170) x 100 % (i.e. an active material utilization of about 81%). This represents a good overall performance for this LiFePO₄ active material.Example 18 - LHP in the presence of iron (III) oxide, elemental iron, and carbon (HMPE) - R1776

[0576] Example 18 was prepared via the blended reaction mechanism at a ratio of 50:50 using 1.58 wt.% excess C.

[0577] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, iron metal (Hoganas AHC300), and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0578] Synthesis Stoichiometric Reaction: UH2PO4 + 0.4442 Fe2O3+ 0.1112 Fe + 0.5767

[0579]

[0580] C LiFePO4+ H2O + 0.3333 CO

[0581] Synthesis Precursor Recipe:

[0582] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0583] 0.4444 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.7097 g

[0584] 0.1112 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.0621 g

[0585] 0.5767 mol C from HMPE [RMM = 12 g / mol] (where proportion of C in HMPE is 0.86) = 0.0805 g

[0586] Pellet mix 5.5 g: LiH2PO4= 2.7822 g, Fe2O3= 1.8990 g, Fe = 0.1662 g, HMPE = 0.2156 g

[0587] Synthesis Conditions: as outlined above for Example 11

[0588] Figure 25A shows the XRD data for Example 18 (ID: R1776). From inspection, it was detected that the sample is close to phase pure LiFePC, with the addition of low-level impurities.

[0589] Figure 25B shows the constant current data for the LiFePC cathode active material for Example 18. As shown in Figure 25B, the second cycle discharge process (lithium re-insertion into the LiFePC ) corresponds to a reversible material specific capacity of 128 mAh / g. The theoretical specific capacity for LiFePC is 170 mAh / g (assuming cycling of one lithium ion per LiFePC formula unit). Thus the 128 mAh / g corresponds to (128 / 170) x 100 % (i.e. an active material utilization of about 75%). This represents a good overall performance for this LiFePC active material.

[0590] Example 19 - LHP in the presence of iron (III) oxide, elemental iron, and carbon (HMPE) - R1777Example 19 was prepared via the blended reaction mechanism at a ratio of 70:30 using 1.58 wt.% excess C.

[0591] Mixture: Lithium dihydrogen phosphate, iron (III) oxide, iron metal (Hdganas AHC300), and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0592] Synthesis Stoichiometric Reaction: UH2PO4 + 0.4651 Fe2O3+ 0.0697 Fe + 0.6405

[0593]

[0594] C LiFePO4+ H2O + 0.3953 CO

[0595] Synthesis Precursor Recipe:

[0596] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0597] 0.4651 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.7428 g

[0598] 0.0697 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.0389 g

[0599] 0.6405 mol C from HMPE [RMM = 12 g / mol] (where proportion of C in HMPE is 0.86) = 0.0894 g

[0600] Pellet mix 5 g: LiH2PO4= 2.6585 g, Fe2O3= 1.9001 g, Fe = 0.0996 g, HMPE = 0.2288 g

[0601] Synthesis Conditions: as outlined above for Example 11

[0602] Figure 26A shows the XRD data for Example 19 (ID: R1777). From inspection, it was detected that the sample is close to phase pure LiFePC, with the addition of low-level impurities.

[0603] Figure 26B shows the constant current data for the LiFePC cathode active material for Example 19. As shown in Figure 26B, the second cycle discharge process (lithium re-insertion into the LiFePC ) corresponds to a reversible material specific capacity of 135 mAh / g. The theoretical specific capacity for LiFePC is 170 mAh / g (assuming cycling of one lithium ion per LiFePC formula unit). Thus the 135 mAh / g corresponds to (135 / 170) x 100 % (i.e. an active material utilization of about 79%). This represents a good overall performance for this LiFePC active material.

[0604] Example 20 - LHP in the presence of iron (III) oxide, elemental iron, and carbon (HMPE) - R1778

[0605] Example 20 was prepared via the blended reaction mechanism at a ratio of 90:10 using 1.58 wt.% excess C.Mixture: Lithium dihydrogen phosphate, iron (III) oxide, iron metal (Hdganas AHC300), and high modulus polyethylene powder (HMPE) (Goonvean Fibres Ltd)

[0606] Synthesis Stoichiometric Reaction: UH2PO4 + 0.4878 Fe2O3+ 0.0244 Fe + 0.7116

[0607]

[0608] C LiFePO4+ H2O + 0.4627 CO

[0609] Synthesis Precursor Recipe:

[0610] 1.000 equivalent LiH2PO4[RMM = 103.9 g / mol] (g): 1.039 g

[0611] 0.4878 equivalent Fe2O3[RMM = 159.7 g / mol] (g): 0.7790 g

[0612] 0.0244 equivalent Fe metal [Atomic Mass = 55.85 g / mol] (g) = 0.0136 g

[0613] 0.7116 mol C from HMPE [RMM = 12 g / mol] (where proportion of C in HMPE is 0.86) = 0.0994 g

[0614] Pellet mix 4.5 g: LiH2PO4= 2.5350 g, Fe2O3= 1.9000 g, Fe = 0.0332 g, HMPE = 0.2424 g

[0615] Synthesis Conditions: as outlined above for Example 11

[0616] Figure 27A shows the XRD data for Example 20 (ID: R1778). From inspection, it was detected that the sample is close to phase pure LiFePC, with the addition of low-level impurities.

[0617] Figure 27B shows the constant current data for the LiFePC cathode active material for Example 20. As shown in Figure 27B, the second cycle discharge process (lithium re-insertion into the LiFePC ) corresponds to a reversible material specific capacity of 130 mAh / g. The theoretical specific capacity for LiFePC is 170 mAh / g (assuming cycling of one lithium ion per LiFePC formula unit). Thus the 130 mAh / g corresponds to (130 / 170) x 100 % (i.e. an active material utilization of about 76%). This represents a good overall performance for this LiFePC active material.

[0618] Ferrothermal Reduction Mechanism - Samples

[0619] Samples prepared using ferrothermal reduction only were tested to provide a frame of reference for subsequent research around the properties of materials produced using controlled blended ferrothermal and carbothermal reduction mechanisms.

[0620] As can be seen from Figure 28, the densities and electrochemical properties of the samples were highly variable.Ferrothermal and Carbothermal Blended Mechanisms - Optimal Carbon Excess

[0621] To determine the optimal carbon excess for methods where a blended carbothermal-ferrothermal (CT: FT) reduction mechanism is desired, the samples of Comparative examples 5 to 7 were prepared.

[0622] The results appear in Figure 29. As can be seen, discharge capacities generally increase with the percentage of excess (Cmoiexcess), showing good results in the range 20 - 100 mol%, with optimal results in the range 50 - 100 mol%.

[0623] The two highest values, 1.58 wt.% and 3.16 wt.% C excess were selected for further study, together with 0 wt% excess, under differing reduction mechanisms across a range of CT: FT ratios.

[0624] CT: FT Ratios Studied

[0625] As noted above, the following Cexcess wt% were taken forward for further study: 0 wt%, 1.58 wt% and 3.16 wt%. They were each tested under the following blended reduction mechanisms:

[0626] CT: FT 0.00 Cexcess wt% - example 14 (blend range 0-90% CT%) and Comparative example 5 (R1769, 100% CT%)

[0627] CT: FT 1.58 Cexcess wt% - example 15 (blend range 0-90% CT%) and Comparative example 6 (R1513, 100% CT%)

[0628] CT: FT 3.16 Cexcess wt% - example 15 (blend range 0-90% CT%) and Comparative example 7 (R1511, 100% CT%)

[0629] Figures 30A, 30B and 30C show the XRD data for the above test series (Figure 30A for CT: FT 0.00 Cexcess wt%, Figure 30B for CT: FT 1.58 Cexcess wt% and Figure 30C for CT: FT 3.16 C excess wt%), indicating that the samples are close to phase pure LiFePC.

[0630] Electrochemistry across CT: FT Ratios

[0631] Figure 31 shows the discharge capacity for the following samples:

[0632] CT: FT 0.00 Cexcess wt% - Example 14 (blend range 0-90% CT%) and Comparative example 5 (R1769, 100% CT%)CT: FT 1.58 Cexcess wt% - Example 15 (blend range 0-90% CT%) and Comparative example 6 (R1513, 100% CT%)

[0633] CT: FT 3.16 Cexcess wt% - Example 15 (blend range 0-90% CT%) and Comparative example 7 (R1511, 100% CT%)

[0634] As can be seen from Figure 31, for electrochemical performance the initial results indicate that the optimal CT: FT ratio is in the range 30 - 100%, with the highest individual values being at 50% and 100% (1.58 and 3.16 C excess wt%) ■

[0635] For blended samples at 0.00 Cexcess wt% (as illustrated by Example 14), there is a clear peak in discharge capacity at 50% CT, with good performance across the range 10% - 90% CT. For blended samples at 1.58 Cexcess wt% and 3.16 Cexcess wt% (as illustrated by Examples 15 and 16), the electrochemistry is consistently good across all CT percentages, although 100% CT% provides the best results (Comparative examples 6 and 7).

[0636] For samples prepared by pure ferrothermal reduction mechanisms (the multiple repeat “diamond” plots as 0 CT% on the x axis), there is a variance in discharge capacity which could be due to synthetic limitations which limit the ability to control the ratios of components. These issues are mitigated where the carbothermal reduction mechanism is present, in even small CT percentages.

[0637] Density across CT: FT Ratios

[0638] Compressed and tap density were measured, with a view to determining whether the observed densities correlated with electrochemical performance.

[0639] Figure 32 shows the compressed densities for the following samples, and Figure 33 the tap densities:

[0640] CT: FT 0.00 Cexcess wt% - Example 14 (blend range 0-90% CT%) and Comparative example 5 (R1769, 100% CT%)

[0641] CT: FT 1.58 Cexcess wt% - Example 15 (blend range 0-90% CT%) and Comparative example 6 (R1513, 100% CT%)

[0642] CT: FT 3.16 Cexcess wt% - Example 15 (blend range 0-90% CT%) and Comparative example 7 (R1511, 100% CT%)

[0643] Compressed DensityThe data shows that the highest densities can be obtained for samples prepared using blended mechanisms, as the results for carbothermal only (100%), are lower than the observed densities in the range 10% - 90% CT. Whilst the density observed for the pure ferrothermal mechanism, is comparable to the best results for the blended systems. However, as noted above the electrochemical behaviour is difficult to reproduce, making preparation using pure ferrothermal mechanisms less desirable than preparation comprising a blend of mechanisms (or that are 100% carbothermal).

[0644] In general, compressed density correlates with CT proportion, reducing gradually as the %CT in the reduction mechanism increases. This correlation is particularly clear for the results produced by 0.00 Cexcess wt% and 1.58 Cexcess wt% (as illustrated by Examples 14 and 15). This indicates that whilst some carbothermal component is desirable for consistency of electrochemical performance, that shifting to a carbothermal dominated mechanism may be undesirable.

[0645] It is also interesting to note that, whilst the samples of Comparative examples 6 and 7 (1.58 Cexcess wt% and 3.16 Cexcess wt%) have high discharge capacities they have poor compressed densities, for instance 2.14 g / cc (1.58 Cexcess wt%) and 2.12 g / cc (3.16 Cexcess wt%).

[0646] Tap Density

[0647] The tap density data confirms the findings with compressed density, in that there is a general correlation between %CT and density, with density reducing as the proportion of carbothermal reduction in the reaction mechanism increases.

[0648] Particle Size across CT: FT Ratios

[0649] Example 1b (R1691), as representative of a sample prepared by an entirely ferrothermal reduction mechanism, was compared to Example 17 (R1695), formed using a CT: FT 50:50 reduction mechanism (Cexcesswt%). The difference in particle size can be seen from Figures 34A and 34B, with smaller particles formed using the blended reduction mechanism, which provides for higher densities as a result of improved particle packing.

[0650] Similar results can be seen with the CT: FT 1.58 Cexcess wt% series (Example 15 0-90% CT% and Comparative example 6 at 100% CT%), as shown in Figure 35, which shows the relative particle sizes for Examples 12 (2.03 pm), 18 (1.99 pm), 19 (1.96 pm), 20 (1.92 pm) and 15 (1.32 pm). A plot is provided in the upper left-hand corner of Figure 35, the observed reduction and ‘knee point’ in particle size as the CT proportion increases reflects a reduction incompressed density as the CT proportion increases (Figure 35 plot) and indicates that a discharge capacity increase can be expected as the CT proportion increases.

[0651] Figure 36 shows the particle size distribution for these samples, indicating that, without being bound by theory, it may be that the blending of the CT: FT mechanisms provides for high polydispersity of particle size, improving packing efficiency and hence density.

[0652] Summary

[0653] In summary, based on electrochemical performance data and density studies, the preparation of materials using a method which provides a blend of carbothermal and ferrothermal reduction mechanisms is desirable to avoid the potential for unpredictable electrochemical performance that can be observed where the mechanism is purely ferrothermal, and the poor densities of high percentage (or even pure) carbothermal mechanisms. By optimising these blends to balance efficiency and performance, it is possible to deliver dense, high-capacity materials without undue narrowing of the process window, making them practical for scale-up.

[0654] Further, it has been observed that, in general, the phase purity of blended samples is superior to those of samples produced using ferrothermal reduction pathways alone. Making them more widely applicable in electrochemical applications with the anticipation of excellent performance.

[0655] Based on the optimisation above, the overall best performance - accounting for phase purity, density and electrochemical performance - appears to be where samples are produced by a method where the reduction mechanism is 30% - 90% (or 50% - 70%) carbothermal reduction, and where the carbon excess (Cexcess wt%) is in the range 0 - 2 (or 0 - 1.6) wt%. This balance outperforms the pure carbothermal samples (100%CT) in terms of density, and the pure ferrothermal samples (0%CT) in terms of electrochemical performance.

[0656] It will be appreciated that the methods, products and uses of the invention are capable of being implemented in a variety of ways, only a few of which have been illustrated and described above.

Claims

CLAIMS1. A method for producing a metal-carbon composite comprising a metal-containing compound and carbon, the method comprising the steps of:a) forming a mixture comprising:i) a carbon source comprising a carbon-containing polymer, pitch, a hydrocarbon, biomass, or combinations thereof;ii) one or more alkali metal precursor compound(s);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 iv) elemental iron and / or Fe-P waste slag;b) heating the mixture under an inert atmosphere to produce a reaction product comprising the metal-carbon composite;wherein during heating step b) the initial average oxidation state of the one or more metals in the metal precursor compound is reduced.

2. The method according to claim 1, wherein the metal-containing compound has the formula:AaMb(XcYd)eZfwherein:A is an alkali metal selected from one or more of lithium, sodium and potassium; M comprises iron and optionally one or more additional metals selected from transition metals, non-transition metals, and metalloids;(XcYd)e is at least one first anion; andZ 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; andwherein Y is selected from one or more halides, sulfur-containing groups, oxygencontaining groups and mixtures thereof.

3. The method according to claim 2, wherein M comprises iron, and optionally one or more additional metals selected from titanium, vanadium, niobium, tantalum, hafnium, chromium, molybdenum, tungsten, manganese, 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 claim 2 or claim 3, wherein f is 0 and Z is absent, or wherein Z is selected from one or more halides, hydroxide-containing groups and mixtures thereof.

5. The method according to any of claims 2 to 4, wherein X comprises phosphorus, optionally wherein (XcYd)e is a PO4 and / or a P2O7 moiety.

6. The method according to any preceding claim, wherein the metal-containing compound is selected from one or more of the group consisting of LiFeP04, NaFeP04, LiMno.5Feo.2Mgo.3PO4, LiFe0.iMn0.9PO4, LiFeo.2Mno.sPO4, LiFeo.3Mno.7PO4, LiFeo.4Mno.5PO4, LiFeo.5Mno.5PO4, LiFe0.95Mgo.o5P04, LiFeo.9Mgo.1PO4, LiFeo.iMgo.osMno.8sP04, LiFeo.2Mgo.osMno.7sP04, Na4Fe3(PO4)2P2O7, LiMno.5Feo.5PO4, Na2Fe(SO4)2, Fe3(PO4)2, Na2FeP2O7, NaFeS04F, LiFeS04F, Li2Fe2(SO4)3, Li2Fe(SO4)2, Na2FePO4F, KFeP04.

7. The method according to any preceding claim, wherein the metal-containing compound has the formula: LiMPO4, where M comprises iron, and optionally one or more additional metals selected from manganese, cobalt, nickel, copper, zinc, magnesium, calcium and combinations thereof.

8. The method according to any preceding claim, wherein the metal-containing compound is selected from LiFePC, LiFei.xMnxPO4, LiFei.xMgxPC>4 and LiFel-x-yMnxMgyPC, wherein 0<x<1 and 0<y<1.

9. The method according to any preceding claim, wherein the one or more metal precursor compound(s) comprises iron and / or manganese.

10. The method according to any preceding claim, wherein the one or more metal precursor compound(s) is selected from one or more of iron (III) oxide (Fe2Os), iron (II, III) oxide(FesC ), iron (III) oxyhydroxide (FeOOH), hydrated iron (III) phosphate (FePC.x W), iron (III) phosphate (FePC ), iron (II) phosphate (Fes(PO4)2), hydrated iron (II) sulfate (FeSC.xFW), iron (III) nitrate (Fe(NOs)3), iron (II) acetate (Fe(CH3CO2)2), iron (III) 2,4- pentanedionate (Fe CsHyC^h wherein x, y are >0), manganese(ll) carbonate (MnCCh), manganese(lll) oxide (M^ j), manganese(IV) oxide (MnC>2), and manganese(ll) hydroxide (Mn(OH)2).

11. The method according to any preceding claim, wherein the one or more alkali metal precursor compound(s) comprises one or more compounds selected from lithium dihydrogen phosphate (IJH2PO4), lithium phosphate (IJ3PO4), lithium metaphosphate (UPO3), lithium carbonate (Li₂CO₃), lithium sulfate (Li₂SO₄), lithium hydrogen phosphate (U2HPO4), and lithium hydroxide (LiOH), or a hydrate thereof, optionally wherein the one or more alkali metal precursor compound(s) further comprises H3PO4, (NF ^HPC, (NH4)H2PO4, or a hydrate thereof.

12. The method according to any preceding claim, wherein the elemental iron and / or Fe-P waste slag is in particulate form, preferably wherein the number average diameter is in the range 1 pm to 1000 pm.

13. The method according to any preceding claim, wherein component iv) comprises elemental iron, and optionally further comprises elemental manganese.

14. The method according to any preceding claim, wherein the elemental iron is selected from iron powder, scrap iron, Direct Reduced Iron (DRI), or a combination thereof.

15. The method according to any preceding claim, wherein the method further comprises the step of pelletising the mixture prior to the heating step b).

16. The method according to any preceding claim, wherein heating the mixture in step b) takes place under nitrogen gas or argon gas.

17. The method according to any preceding claim, wherein heating step b) takes place at a temperature in the range 200 °C to 1500 °C, optionally for a period in the range 240 minutes to 600 minutes.

18. The method according to any preceding claim, wherein the carbon source comprises a carbon-containing polymer, optionally wherein the carbon-containing polymer is selectedfrom polyethylene (PE), Polypropylene (PP), High-Modulus Polyethylene (HMPE), High- Density Polyethylene (HDPE), Low-Density Polyethylene (LDPE), High-Modulus Polypropylene (HMPP), High-Density Polypropylene (HDPP), Low-Density Polypropylene (LDPP), Polyvinyl Chloride (PVC), Polyethylene Terephthalate (PET), Polystyrene (PS), Polyethylene Glycol (PEG), Polyvinylidene Fluoride (PVdF), Polyvinylidene Fluoride-Hexafluoropropylene (PVdF-HFP), Polyacrylonitrile (PAN), Polyvinyl Alcohol (PVA), Polytetrafluoroethylene (PTFE), a polycarbonate, a polyamide, or combinations thereof.

19. The method according to any of claims 1 to 17, wherein the carbon-containing polymer comprises an elastomer obtained from rubber, optionally wherein the rubber is tyre rubber, such as de-vulcanized tyre rubber.

20. The method according to any preceding claim, wherein the carbon-containing polymer comprises a halogen selected from Cl, Br, F, or I.

21. The method according to claim 20, wherein the carbon-containing polymer is selected from the group consisting of PVdF, PVdF-HFP, PVC, or a combination thereof.

22. The method according to any preceding claim, wherein the carbon-containing polymer is in particulate form, preferably, wherein the number average diameter is less than 20 pm.

23. The method according to any preceding claim, wherein the carbon source comprises pitch, optionally wherein the pitch comprises coal tar pitch, asphalt, bitumen, or combinations thereof.

24. The method according to claim 23, wherein the pitch is soluble in a solvent, optionally wherein the method comprises mixing the pitch in a solvent, followed by evaporating the solvent prior to or during heating step b).

25. The method according to claim 24, wherein the solvent is a polar solvent, optionally selected from acetone or water.

26. The method according to any preceding claim, wherein the carbon source comprises biomass, optionally wherein the biomass comprises at least one fraction derived from bio-oil, wherein the at least one fraction derived from bio-oil comprises bioasphaltene, biomaltene, or a combination thereof.

27. The method according to any preceding claim, wherein the carbon source comprises particulate carbon, optionally wherein the particulate carbon is selected from carbon black, hard carbon, activated carbon, charcoal, coke, graphite, graphene, carbon nanotubes, carbon nanofibers, or combinations thereof.

28. The method according to any preceding claim, wherein the carbon source comprises a carbon-containing polymer, pitch, a hydrocarbon, or combinations thereof; and wherein the metal-carbon composite formed is a carbon-coated metal-containing compound.

29. The method according to claim 28, wherein at least a portion of the carbon coating comprises sp2carbons.

30. The method according to claim 28, wherein the carbon source comprises pitch and / or a carbon-containing polymer; and wherein heating step b) is a multi-step heating step comprising heating the mixture to a first temperature proximate to or above the melting point of the pitch and / or carbon-containing polymer, and heating at a second temperature sufficient to convert the pitch and / or carbon-containing polymer to carbon, optionally wherein the first temperature is in the range of 50 °C to 250 °C and wherein the second temperature is in the range of 300 °C to 1500 °C, and optionally wherein the first temperature is maintained for a period of 1 to 100 minutes and the second temperature is maintained for a period of 1 to 500 minutes.

31. The method according to claim 30, wherein at least part of the pitch and / or carbon- containing polymer is converted to elemental carbon during heating at the second temperature, optionally, wherein at least part of the pitch and / or carbon-containing polymer is converted to sp2carbon.

32. The method according to any preceding claim, wherein the metal-carbon composite has a total carbon content in the range 1 to 5% by weight carbon.

33. An electrode active material made according to the method of any one of claims 1 to 32.

34. A battery comprising an electrode comprising a metal-carbon composite produced according to the method of any one of claims 1 to 32, optionally wherein the battery is a rechargeable battery, optionally wherein the battery is an alkali metal ion battery, such as a lithium-ion battery.

35. Use of a metal-carbon composite produced according to the method of any one of claims 1 to 32 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.

36. Use of a carbon source comprising a carbon-containing polymer, pitch, particulate carbon, a hydrocarbon, or combinations thereof, and elemental iron and / or Fe-P waste slag in a ferrothermal assisted carbothermal reduction reaction of a metal precursor compound to produce a metal-carbon composite.

37. Use according to claim 36, wherein the ferrothermal assisted carbothermal reduction reaction will comprises in the range 30% - 90% carbothermal contribution to the reduction mechanism.

38. A composition comprising LiFePO₄ in particulate form prepared according to the method of any one of claims 28 to 32, wherein the particles are at least partially coated with a carbon coating, and wherein at least a portion of the carbon coating comprises sp2carbons.

39. A composition comprising LiFe₁₋ₓMnₓPO₄ in particulate form prepared according to the method of any one of claims 28 to 32, wherein the particles are at least partially coated with a carbon coating, and wherein at least a portion of the carbon coating comprises sp2carbons.

40. A method for producing a metal-carbon composite comprising a carbon-coated metalcontaining compound, the method comprising the steps of:a) forming a mixture comprising:i) a carbon source comprising a carbon-containing polymer, pitch, a hydrocarbon, or combinations thereof;ii) one or more alkali metal precursor compound(s);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 iv) elemental iron and / or Fe-P waste slag;b) heating the mixture under an inert atmosphere 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; andwherein at least a portion of the carbon coating comprises sp2carbons.

41. The method according to claim 41, wherein the carbon source further comprises particulate carbon.

42. Use of a carbon source comprising a carbon-containing polymer, pitch, a hydrocarbon, or combinations thereof and elemental iron and / or Fe-P waste slag in a ferrothermal assisted 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 sp2carbons.

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