Method for making lithium metal phosphate

Abstract

Formula Li x M 1-z D z 1. A method for making a material of formula (I), wherein M is one or more transition metals and D represents one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements, and 0.8≦x≦1.2 and 0≦z≦0.2, comprising the steps of: a) forming a mixture comprising a source of one or more transition metals, a source of phosphorus, a source of lithium, and a surfactant, and optionally a source of D; (i) forming a material having a ratio of Li:PO4:(M+D) relative to the stoichiometry required to form the material in the range of 1.04-1.10:1.00-1.05:1, or (ii) a ratio of (Li+PO4):(M+D) relative to the stoichiometry required to form the material greater than 2.05; b) drying the mixture from step (a) to form particles or powder; and c) heat treating the particles or powder from step (b) to form the material.

Description

[Technical Field]

[0001] The present invention relates to a method for making lithium metal phosphate. [Background technology]

[0002] Lithium metal phosphates, such as lithium iron phosphate, are widely used in the manufacture of lithium ion batteries due to their high energy density, good stability, ability to withstand many charge / discharge cycles, and relatively low cost.

[0003] Where a prior art publication is referenced herein, it is expressly understood that this reference does not constitute an acknowledgment that the publication forms part of the common general knowledge in the art in Australia or any other country. Summary of the Invention

[0004] In one aspect, the present invention provides a compound of formula Li x M 1-z D z 1. A method for making a material of PO4, wherein M is one or more transition metals and D represents one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements, and 0.8≦x≦1.2 and 0≦z≦0.2; a) forming a mixture comprising a source of one or more transition metals, a source of phosphorus, a source of lithium, and a surfactant, and optionally a source of D, wherein the mixture (i) has a ratio of Li:PO4:(M+D) relative to the stoichiometry required to form the material in the range of 1.04-1.10:1.00-1.05:1, or (ii) has a ratio of (Li+PO4):(M+D) relative to the stoichiometry required to form the material greater than 2.05; b) drying the mixture from step (a) to form particles or a powder; c) heat treating the particles or powder from step (b) to form the material.

[0005] In one embodiment, M is one or more transition metals selected from Fe, Mn, Ni, Co, Cr, or V. In one embodiment, M is Fe. In one embodiment, M comprises Fe and one or more of Mn, Ni, Co, Cr, or V. In one embodiment, M comprises two or more of Fe, Mn, Ni, Co, Cr, or V.

[0006] In one embodiment, the process comprises: d) mixing the material from step (c) with a liquid containing a carbon precursor; e) spray drying the mixture from step (d) to form particles of the carbon precursor coated material; f) converting the carbon precursor into carbon.

[0007] In one embodiment, the mixture formed in step (a) comprises a liquid. In one embodiment, the liquid comprises water. In one embodiment, the liquid comprises demineralized or deionized water.

[0008] In one embodiment, the mixture formed in step (a) comprises a solution in which one or more sources of transition metal, a source of phosphorus, and a source of lithium are dissolved, and, if present, a source of D.

[0009] In another embodiment, the mixture formed in step (a) comprises a slurry in which one or more of the source of transition metal, source of phosphorus, or source of lithium, or the source of D, if present, are present as particulate matter. In one embodiment, the source of one or more transition metals are present as particulate matter. In this embodiment, the particulate matter remains or remains as particulate matter during the mixing and drying steps. In one embodiment, the source of one or more transition metals is a source of iron, and the source of iron is present as particulate matter in the mixture. Prior art methods known to the inventors for forming lithium metal phosphate typically involve forming a solution in which all precursor compounds are dissolved. Some of the precursor compounds may be difficult to dissolve, and / or forming a solution may require additional reactants or additional processing steps. As a result, the inventors believe that a process according to the present invention in which the mixture of step (a) comprises a slurry is particularly advantageous because it may result in one or more of reduced processing steps, fewer reactants, or simple processing.

[0010] In embodiments in which one or more of the sources of transition metal, phosphorus, or lithium, or, if present, the source of D, are present as particulate matter, the particulate matter or slurry may be milled before drying. In one embodiment, the particulate matter or slurry is milled in a bead mill or a tumbling mill. Other milling processes may be used. The milling step may reduce the size of the particulate matter and may intimately and homogeneously mix the particulate matter with the other components of the slurry.

[0011] In one embodiment, the source of the one or more transition metals comprises one or more sources of Fe, Mn, Ni, Co, Cr, or V. In one embodiment, the source of the one or more transition metals comprises one or more compounds containing a transition metal, which may include M+2 salts such as chlorides and sulfates, M+3 salts such as chlorides, nitrates, sulfates, organic M salts such as M-oxalates, M-citrates, M-phosphates, M-oxides, metal M, or other M-containing compounds.

[0012] In one embodiment, the source of one or more transition metals includes a source of iron. In this embodiment, the source of iron can include an iron-containing compound. While any suitable iron-containing compound can be used, it is desirable that the iron-containing compound have iron in the form of iron(II). Iron(II) oxalate dihydrate is one example of a suitable iron-containing compound. The source of iron can be a mineral Fe+2 salt (e.g., FeCl2, FeSO4, etc.), a mineral Fe+3 salt (e.g., FeCl3, Fe(NO3)3, Fe2(SO4)3, etc.), an organic Fe salt (e.g., Fe oxalate, Fe citrate, etc.), an Fe phosphate (e.g., FePO4, Fe3(PO4)2), an Fe oxide (e.g., magnetite, hematite, etc.), metallic Fe, or other Fe-containing compounds.

[0013] In one embodiment, the phosphorus source comprises a phosphorus-containing compound or a phosphorus-containing acid. In one embodiment, the phosphorus source comprises phosphoric acid. The phosphorus source can be phosphoric acid, a lithium-containing phosphoric acid (e.g., LiPO, LiHPO, LiHPO), an organic phosphate (e.g., (NH)PO, (NH)HPO, NHHPO), or other phosphate-containing compounds.

[0014] The source of lithium can be a carbonate (e.g., Li2CO3, LiHCO3), a phosphate (e.g., Li3PO4, Li2HPO4, LiH2PO4), a hydroxide (e.g., LiOH), a mineral lithium salt (e.g., LiCl, LiNO3, Li2SO4, etc.), an organic mineral salt (e.g., Li acetate, lithium oxalate, etc.), metallic Li, or other lithium-containing compounds. In one embodiment, the source of lithium includes lithium carbonate.

[0015] In one embodiment, the source of D may include one or more water-soluble compounds containing D, or one or more water-insoluble compounds containing D (including oxides), or mixtures thereof.

[0016] The inventors have surprisingly found that when the amount of Li exceeds the stoichiometric amount and the amount of PO exceeds the stoichiometric amount but is less than the amount of Li, a better performing material, such as LiMPO, can be obtained when the amounts of Li and PO are expressed relative to the amounts of M or M+D. In other words, the ratios of Li, PO, and M or M+D in the mixture, when expressed in stoichiometric amounts, are such that the input ratio is Li > PO > M (or M+D). For example, Li can be present in a stoichiometric amount of about 1.04 to 1.10, PO can be present in a stoichiometric amount of about 1.00 to 1.05, and M (or M and D) can be present in a stoichiometric amount of about 1.00. PO in this context also refers to a PO precursor. In one embodiment, the ratios of each of Li, PO, and M (or M and N) in the mixture, when expressed as a stoichiometric ratio, are such that the input ratio is Li>PO>M, or Li is present in a stoichiometric amount of about 1.05, PO is present in a stoichiometric amount of about 1.02, and M (or M and N) is present in a stoichiometric amount of about 1.00.

[0017] In one embodiment, the ratio of Li:PO4:(M+D) relative to the stoichiometry required to form the material is in the range of 1.05-1.09:1.00-1.04:1. In one embodiment, the ratios of each of Li, PO4, and M (or M and D) in the mixture, when expressed as a ratio of stoichiometric amounts, are such that the input ratio is Li>PO4>M, or Li is present in a stoichiometric amount of about 1.07, PO4 is present in a stoichiometric amount of about 1.02, and M (or M and D) is present in a stoichiometric amount of about 1.00. In one embodiment, the ratios of each of Li, PO, and M (or M and D) in the mixture, when expressed as a stoichiometric ratio, are such that the input ratio is Li>PO>M, or Li is present in a stoichiometric amount of about 1.05, PO is present in a stoichiometric amount of about 1.02, and M (or M and D) is present in a stoichiometric amount of about 1.00.

[0018] In other embodiments, the ratio of (Li+PO4):(M+D) relative to the stoichiometry required to form the material is greater than 2.05, or more preferably in the range of 2.07 to 2.13.

[0019] In one embodiment, the present invention provides a method for making a lithium metal phosphate of formula LiMPO4, wherein M is one or more transition metals; a) forming a mixture comprising water, one or more sources of transition metals, a source of phosphorus, a source of lithium, and a surfactant, wherein the mixture formed in step (a) comprises a slurry in which one or more of the sources of transition metals, the source of phosphorus, or the source of lithium are present as particulate matter, the mixture having an amount of Li in excess of the stoichiometric amount, an amount of PO4 in excess of the stoichiometric amount but less than the amount of Li, the amounts of Li and PO4 being set forth relative to the amount of M; b) spray drying the mixture from step (a) to form particles or a powder; and c) heat treating the particles or powder from step (b) to form lithium metal phosphate.

[0020] In one embodiment, the mixture of step (a) comprises a solution, and forming the solution comprises mixing a solvent or reactant with water and particles of one or more of an iron source, a phosphorus source, or a lithium source, thereby dissolving the particles of the one or more of the iron source, the phosphorus source, or the lithium source. In one embodiment, one or more of the iron source, the phosphorus source, or the lithium source are sparingly soluble in water. In one embodiment, the iron source is sparingly soluble in water, and the solvent or reactant dissolves or reacts with the iron source, thereby placing the iron in solution.

[0021] In one embodiment, the mixture formed in step (a) further comprises oxalic acid, and the mixture of step (a) comprises a solution formed by mixing water and a source of oxalic acid and iron with a solvent or reactant that dissolves or reacts with the source of oxalic acid and iron, thereby solubilizing the source of oxalic acid and iron, adding a source of phosphorus, and then adding a source of lithium, thereby forming a solution. A surfactant may then be added to the solution to form the mixture of step (a) in liquid form.

[0022] In one embodiment, the mixture of step (a) comprises water present in an amount of 25% to 75% by weight of the total weight of the mixture.

[0023] In one embodiment, the surfactant is present in an amount of 0.05% to 10% by weight of the mixture, or 1% to 4% by weight of the total mixture, or about 1.4% to 2.8%.

[0024] In one embodiment, the one or more transition metal sources may comprise between 5% and 40% by weight of the mixture, or between 10% and 35% by weight of the mixture, or between 15% and 30% by weight of the mixture.

[0025] In one embodiment, the source of phosphorus is present in an amount from 5% to 30% by weight of the mixture, or from 5% to 25% by weight of the mixture, or from 9% to 20% by weight of the mixture.

[0026] In one embodiment, the source of lithium is present in an amount between 2% and 21% by weight of the mixture, or between 2% and 10% by weight of the mixture, or between 2.5% and 8% by weight of the mixture, or between about 3% and 7% by weight of the mixture.

[0027] When present, the source of D is typically present in an amount commensurate with the requirements of the final composition of matter.

[0028] In embodiments where the mixture contains other components, such as a solvent and / or other reactants or other materials, the other components may be present in an amount from 15% to 35% by weight of the mixture, or from 17% to 30% by weight, or from 20% to 30% by weight of the mixture.

[0029] In one embodiment, the mixture of step (a) comprises a solution of water, iron (II) oxalate dihydrate, oxalic acid dihydrate, hydrogen peroxide, phosphoric acid, and lithium carbonate, to which a surfactant has been added.

[0030] In one embodiment, the mixture of step (a) comprises a slurry containing particulate matter. In one embodiment, the slurry comprises iron(II) oxalate dihydrate particles, phosphoric acid, lithium carbonate, water, and a surfactant. In one embodiment, phosphoric acid is added to water, followed by lithium carbonate, which reacts / dissolves. Iron oxalate is then added to form a slurry, and the slurry is then subjected to milling. The surfactant is added during or after milling. In one embodiment, the surfactant is added after milling. In another embodiment, the slurry can be made by mixing iron(II) oxalate dihydrate particles with water in a milling mill, milling, adding lithium carbonate and phosphoric acid to the mill to form a slurry, and then mixing the slurry with a surfactant to form a mixture.

[0031] The surfactant may include a nonionic surfactant, an anionic surfactant, or a cationic surfactant. In one embodiment, the surfactant includes a nonionic surfactant. In one embodiment, the surfactant includes an ethoxylate surfactant or an alkoxylate surfactant. In one embodiment, the surfactant includes an alcohol ethoxylate or an ethoxylated lauryl alcohol surfactant. Other surfactants that may be used include polyoxyethylene (4) lauryl ether, octylphenol ethoxylate, and ethylene / propylene oxide-based block copolymers. Other surfactants, such as lipids, may also be used.

[0032] Step (b) of the present invention comprises drying the mixture from step (a). In one embodiment, step (b) comprises spray drying.

[0033] In one embodiment, a surfactant is added to form the mixture of step (a) in a tank prior to the dryer or spray dryer.

[0034] The spray dryer can be any spray dryer known to be suitable to one of ordinary skill in the art, hi one embodiment, the spray dryer comprises a rotating disk spray dryer or disk atomizer.

[0035] In one embodiment, the inlet gas temperature to the dryer has a temperature of 150°C to 500°C, or 175°C to 350°C, and the dryer outlet gas has a temperature of 50°C to 150°C, or 80°C to 120°C.

[0036] The spray drying process produces a dry, free-flowing powder with high product recovery. The inventors have found that including a surfactant in the mixture to be spray-dried in step (b) is essential, because tests performed without the surfactant produced a wet powder with poor product recovery due to the accumulation of sticky powder in the drying chamber of the spray dryer. The inventors have also used polyethylene glycol instead of a surfactant, but these tests did not produce satisfactory results.

[0037] In other embodiments, the dryer may include a fluidized bed dryer, a rotary dryer, a rotary bed dryer, a conduction dryer, a convection dryer, a toroidal bed dryer, a vacuum dryer, or a dispersion dryer.

[0038] In some embodiments, the mixture of step (a) is dried in step (b), and the dried product may need to be broken down into smaller particles or powder, such as by grinding or vibrating.

[0039] The powder produced in step (b) is a precursor powder or precursor particulate material. This precursor powder / particulate material is then heat treated to produce particles of a material having the formula Li x M 1-z D zPO4, where x and z are as defined herein above. The heat treatment of step (c) is suitably carried out in an oxygen-free atmosphere, such as a nitrogen atmosphere or an inert atmosphere. In some embodiments, step (c) can include passing the powder / particulate material from step (b) through an environment having a temperature of 400-600°C, or 450-500°C, or 450-480°C. The powder / particulate material can be heated long enough to ensure essentially complete conversion to the material. In some embodiments, the powder / particulate material can be treated in a reactor or furnace for 5 minutes to 6 hours, or 10 minutes to 3 hours, or 20 minutes to 2 hours, or 30 minutes to 1 hour, or about 45 minutes.

[0040] In embodiments in which one or more of the source of one or more transition metals, the source of phosphorus, or the source of lithium, or the source of D, if present, is present as particulate matter, the particulate matter remains particulate matter after the drying or spray drying step, and the particulate matter then participates in a reaction to form lithium metal phosphate.

[0041] The raw powder of material formed in step (c) may comprise particles formed as agglomerates of crystallites, the crystallites having particle sizes in the range of 10 to 200 nm, or 20 to 100 nm.

[0042] Preliminary tests conducted by the present inventors have shown that the crystallites formed in step (c) may have a particle size distribution with a primary particle (or crystallite) size in the range of 10 to 200 nm, or 20 to 100 nm, and the aggregates formed in step (c) may have a d of 1 to 10 μm. 10 , 5-50 μm d 50 , and d of 10 to 100 μm 90 It was shown that the particle size distribution was

[0043] In one embodiment, the present invention provides a compound of formula Li x M 1-z D z 1. A method for making a material of formula PO4, wherein M is one or more transition metals; a) forming a mixture comprising one or more sources of transition metals, a source of phosphorus, a source of lithium, optionally a source of D, and a surfactant, wherein the mixture comprises a slurry, and one or more of the one or more sources of transition metals, phosphorus, or lithium, or the source of D, if present, is present as a particulate material, and wherein (i) the ratio of Li:PO4:(M+D) to the stoichiometry required to form the material is within the range of 1.04-1.10:1.00-1.05:1, or (ii) the ratio of (Li+PO4):(M+D) to the stoichiometry required to form the material is greater than 2.05; b) drying the mixture from step (a) to form a powder; c) heat treating the powder from step (b) to form the material.

[0044] In this embodiment, the particles may persist in steps (a) and (b) and participate in a reaction to form a substance in step (c). In this embodiment, M, D, x, and z may be as described above.

[0045] In another embodiment, the present invention provides a compound of formula Li x M 1-z D z 1. A method for making a material of formula PO4, wherein M is one or more transition metals; a) forming a mixture comprising a source of one or more transition metals, a source of phosphorus, a source of lithium, optionally a source of D, and a surfactant, wherein the one or more transition metals, the source of phosphorus, the source of lithium, and, if present, the source of D, are dissolved in solution, and (i) the ratio of Li:PO4:(M+D) to the stoichiometry required to form the material is within the range of 1.04-1.10:1.00-1.05:1, or (ii) the ratio of (Li+PO4):(M+D) to the stoichiometry required to form the material is greater than 2.05; b) spray drying the mixture from step (a) to form a powder; c) heat treating the powder from step (b) to form the material.

[0046] In this embodiment, M, and D, and x, and z may be as described above.

[0047] The material produced in step (c) may require further densification and / or processing before end use. For example, lithium iron phosphate is known to have poor electrical conductivity. Therefore, it may be desirable to further process the material from step (c) to improve its electrical conductivity. In one embodiment, particles of the material from step (c) are (d) mixed with a liquid containing a carbon precursor, (e) the mixture is then spray-dried to form particles of lithium metal phosphate coated with the carbon precursor, and (f) the particles are subsequently treated to convert the carbon precursor to carbon.

[0048] In some embodiments, step (d) comprises mixing the material from step (c) with a liquid containing a carbon precursor. The liquid containing the carbon precursor may comprise a solvent containing a dissolved carbon precursor. In one embodiment, the liquid containing the carbon precursor comprises an aqueous solution containing a dissolved carbon precursor. The dissolved carbon precursor may comprise a sugar. The sugar may comprise sucrose, although other sugars such as fructose, glucose, and lactose may also be used. In other embodiments, other water-soluble carbon precursors may be used in place of or in addition to the sugar. Other carbon precursors that may be used in embodiments of the invention include starch, maltodextrin, gelatin, other sugars including mannose and galactose, and polymers of at least partially water-soluble monomers such as polyacrylates.

[0049] In other embodiments, an organic solvent may be used to dissolve a carbon precursor that is soluble in the organic solvent, such as a polymer or monomer, thereby coating particles of the material with the carbon precursor. However, the use of an aqueous solution containing a dissolved carbon precursor is preferred because aqueous solutions have easier handling and occupational health and safety requirements compared to organic solutions.

[0050] In some embodiments, the material produced in step (c) is milled in a liquid containing a carbon precursor to break down any large agglomerates, densify the material, and simultaneously coat the particles of the material with the carbon precursor. In some embodiments, the milling step involves milling a slurry containing 5-50 wt% solids, or 10-30 wt% solids, or 15-25 wt% solids, to produce particles with a diameter of 200 nm to 400 nm, or 250-350 nm. 50 This is done by reducing it to

[0051] In embodiments in which a sugar solution is used, the sugar solution may comprise between 2% and 10% sugar by weight, or between 3% and 7% sugar by weight, or between 4% and 6% sugar by weight.

[0052] Once the particles of material are coated with the carbon precursor, they are then spray dried to form agglomerates of the desired shape and particle size. The spray drying step can include transferring the slurry from step (d) to a feed tank of a spray dryer. The slurry can be diluted to a solids content of 5% to 30% by weight, or 7% to 25% by weight, or 10% to 20% by weight in the feed tank of the spray dryer or in a separate tank located upstream of the spray dryer.

[0053] In some embodiments, the slurry in the feed tank to the spray dryer is spray dried using an air atomizing nozzle operating at a pressure of 2-5 bar or 3-4 bar, an inlet gas temperature in the drying chamber in the range of 150°C-500°C or 175-245°C, or about 190°C, and an outlet temperature of 50-150°C, or 70-110°C, or 80-100°C, or about 90°C.

[0054] This spray drying process results in the formation of a free-flowing powder consisting of agglomerates of material coated with the carbon precursor. In embodiments where the carbon precursor comprises a sugar, a free-flowing powder consisting of agglomerates of material coated with the sugar is obtained.

[0055] The particles or aggregates formed in this step may have an average particle size of less than 10 μm, or from 2.5 μm to less than 10 μm, or from 5 to 8 μm, or from 6 to 7 μm. 10 is 2 to 4 μm, and d 50 is 5 to 10 μm, and d 90 The particle size distribution may be 10 to 20 μm.

[0056] The carbon precursor coating on the aggregates is then converted to carbon in step (f). The aggregates may be dried and then heated under a non-reactive or inert atmosphere, such as under a nitrogen or inert gas atmosphere, to carbonize the carbon precursor. For example, the aggregates may be placed in a furnace operated at a temperature of 500°C to 1000°C, or 600°C to 900°C, or 700°C to 800°C, or about 750°C, for a time long enough to carbonize the carbon precursor. In some embodiments, the aggregates may be held at an elevated temperature for 30 minutes to 6 hours, 45 minutes to 5 hours, or 1 hour to 4 hours, or 1.5 hours to 3 hours, or about 2 hours.

[0057] Step (f) converts the carbon precursor to carbon, resulting in the formation of particles of material having a coating of carbon thereon, or a uniform coating of carbon thereon. The particles can be packaged in sealed bags or containers under a dry atmosphere to avoid moisture absorption, and prepared for shipment to a customer.

[0058] Any of the features described herein may be combined in any combination with any one or more of the other features described herein within the scope of the present invention.

[0059] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or in any way an indication that the prior art forms part of the common general knowledge. DETAILED DESCRIPTION OF THE INVENTION

[0060] Example 1 - Generation of LFPs using the solution in step (a) The following general procedures were used in the examples:

[0061] (1) Preparation of precursor solution mixture The process used for the preparation of the precursor mixture is as follows: Weigh out the required mass of raw materials for the batch, including demineralized water, oxalic acid dihydrate, iron(II) oxalate dihydrate, phosphoric acid, lithium carbonate, hydrogen peroxide, and ethoxylated lauryl alcohol surfactant. Transfer the demineralized water to a mixing tank with a cooling jacket and start the tank agitator. Add oxalic acid to the mixing tank and continue to stir the mixture which forms a slurry at ambient temperature due to the low solubility of oxalic acid crystals. Add the iron(II) oxalate to the mixing tank while continuing to mix the slurry to keep the solid particles well suspended. Start the flow of cooling water through the mixing tank jacket and begin the controlled dosing of hydrogen peroxide to prevent the mixture temperature from rising above 70°C due to the exothermic reaction. Once the hydrogen peroxide dosage is complete, continue stirring the mixture until all of the iron(II) oxalate has dissolved, resulting in a particle-free coffee-colored solution. • Continue stirring and cooling the solution until the temperature drops below 50°C. Add phosphoric acid to the mixture and continue stirring until the color of the solution changes from coffee to green. Stop cooling when the solution temperature drops below 40°C. Add the lithium carbonate powder to the solution while continuing to stir and monitor the mixture until all the lithium carbonate is dissolved. Add the ethoxylated lauryl alcohol surfactant to the green precursor solution and continue stirring until thoroughly dispersed.

[0062] (2) Spray drying of the precursor mixture The precursor mixture obtained from step (1) is spray-dried to obtain a yellow precursor powder as follows: Transfer the precursor mixture to the feed tank of the spray dryer Heat the spray dryer to obtain stable operation at the required inlet and outlet gas temperatures using demineralized water as the liquid medium Switch the spray dryer feed from demineralized water to precursor mix and fine-tune the spray dryer operating conditions to maintain stable operation at the desired temperature setpoint Collect the separated spray-dried yellow precursor powder from the spray dryer exit gas stream and store it under a dry gas atmosphere to limit moisture absorption

[0063] (3) Formation of raw LFP The yellow precursor powder obtained from step (2) is heat-treated in an oxygen-free atmosphere to produce the starting LFP intermediate as follows: Heat the reactor to 480°C and purge the reactor with nitrogen to exclude oxygen. Transfer the precursor powder to the feed hopper of the thermal reactor and purge with nitrogen to exclude oxygen. Start the thermal reactor mixer and transfer the precursor powder from the feed hopper to the reactor The precursor powder is heated to 450°C, and then heated at 450-480°C for another 45 minutes until the powder is completely converted into raw LFP powder. • Transfer the raw LFP from the thermal reactor to an oxygen-free atmosphere until it cools to below 60°C, and then store the raw LFP.

[0064] (4) Densification of raw LFP, carbon coating, and spray drying The raw LFP is milled in a sucrose solution to break down spongy agglomerates and densify the LFP while simultaneously coating the milled particles with a carbon-rich precursor. The milled slurry is then spray-dried to form agglomerates of the desired shape and particle size. The process is as follows: Weigh out the required amounts of demineralized water, raw LFP, and sucrose. Transfer the demineralized water to the bead mill's supply tank and start the tank mixer. Add sucrose to the bead mill feed tank and continue mixing until the sucrose is dissolved. Start the pump that circulates the bead mill and sucrose solution from the supply tank to the bead mill, and establish stable circulation and grinding operation. • Begin adding raw LFP to the feed tank and continue dosing all of the LFP while maintaining a stable grinding operation, resulting in a slurry containing 20% ​​solids. Mill the slurry for 60-90 minutes until the particle size is reduced to D50 of 250-350 nm. Transfer the milled slurry to the spray dryer's feed tank Establish stable spray dryer operation at the required inlet and outlet temperatures of demineralized water before switching the spray dryer feed to milled slurry Collect the separated agglomerated sucrose-coated LFP from the spray dryer exit gas stream and store for further processing.

[0065] (5) Heating the spray-dried LFP in an oven The spray-dried LFP aggregates are heated in a furnace under a nitrogen atmosphere to carbonize the sucrose and form a conductive carbon network as follows: Place the spray dried LFP powder into ceramic and / or graphite trays with a maximum of 2.5 kg of LFP per tray and position in the central zone of the tube furnace and seal the furnace. The LFP was vacuum dried by drawing a vacuum of 30-50 mbar in the furnace and heating it to 160°C for 60 minutes. Once the drying process is complete, the furnace is refilled with dry nitrogen gas up to atmospheric pressure, and the heating cycle begins at a process temperature setpoint of 750°C. Purge with a small continuous stream of nitrogen gas throughout the heating cycle, which includes a 2-hour soak at 750°C followed by a cool down to below 60°C. The LFP is removed from the furnace and packed in sealed bags / containers under a dry atmosphere to avoid moisture absorption and ready for shipment to the customer.

[0066] The above general procedure was used in the following examples:

[0067] Example 1A Lithium iron phosphate (LFP) was prepared at pilot plant scale using the raw material formulation shown below, with a total mix mass of 204 kg.

[0068] Input chemicals Component % (weight %) Oxalic acid dihydrate 17.20 Demineralized water 26.80 Fe(II) oxalate 21.74 50% H2O2 13.03 85% H3PO413.97 Lithium carbonate 4.53 Ethoxylated Lauryl Alcohol Surfactant 2.73

[0069] Oxalic acid was added to demineralized water in a stirred tank to form a suspended slurry. Iron(II) oxalate was then added to the stirred slurry. Hydrogen peroxide was dosed at a controlled rate while cooling the jacketed tank to maintain the tank contents at 70°C. A mixture of soluble iron(III) oxalate was formed as a coffee-colored solution with excess oxalic acid chelating agent present. The mixture was cooled to 50°C, and then phosphoric acid was added, changing the solution color to green. When the temperature of the tank contents reached 40°C, cooling was discontinued and lithium carbonate powder was dosed into the stirred tank, where it completely dissolved in approximately 5 minutes.

[0070] The solution was pumped into the spray dryer's feed tank, where the ethoxylated lauryl alcohol surfactant was added and thoroughly dispersed using a tank mixer. The solution was spray-dried using a disk atomizer with a drying chamber inlet gas temperature of 300°C. The addition of the ethoxylated lauryl alcohol surfactant resulted in a dry, free-flowing yellow powder and high product recovery, in contrast to experiments without the ethoxylated lauryl alcohol surfactant, which produced a wet powder with approximately two-thirds of the product lost due to the buildup of sticky powder in the drying chamber. The dry, free-flowing powder was stored under a nitrogen atmosphere to prevent oxidation. The powder was heat-treated in a nitrogen-purged, mechanically fluidized reactor at 450°C for 45 minutes, producing an LFP with a crystallite size of approximately 50 nm and a phase purity of greater than 99%.

[0071] LFP was mixed with demineralized water to form a slurry with 25% (m / m) solids, and sucrose was added at a dosage of 4.2% of the LFP mass. The slurry was milled in a bead mill equipped with 0.5 mm beads for 110 minutes to reduce the LFP particle size to a D50 of 350 nm. The slurry was transferred to the feed tank of a spray dryer, where demineralized water was added to reduce the slurry to 13% (m / m) solids. The slurry was spray-dried using an air atomizing nozzle operating at a pressure of 3.2 bar, a drying chamber inlet gas temperature of 190°C, and an outlet temperature of 90°C. A free-flowing powder consisting of sucrose-coated LFP agglomerates was obtained.

[0072] The powder was placed in a graphite crucible in a pilot-scale tube furnace and dried under vacuum at 160°C for 60 minutes. After drying, the vacuum atmosphere was replaced with nitrogen gas (99.99%) and the furnace temperature was increased to 700°C over 60 minutes. The LFP was held under nitrogen and subjected to a 120-minute soak time at 700°C to convert the sucrose to carbon and sinter the LFP to a crystallite size of approximately 110 nm. The furnace was allowed to cool to below 60°C over 12 hours before the LFP was removed from the tray and packaged in sealed foil bags under a dry atmosphere.

[0073] The LFP was subjected to physical, chemical, and electrochemical characterization, and the results are tabulated below. Physical and chemical properties indicated that it provided satisfactory electrode fabrication properties, and electrochemical testing confirmed a capacity of 160 mAh / g and 75% retention at a charge / discharge rate of 5C. [Table 1] [Table 2]

[0074] Example 1B Lithium iron phosphate (LFP) was prepared at pilot plant scale using the raw material formulation shown below with a total mixed mass of 201 kg. The dosage of ethoxylated lauryl alcohol surfactant was reduced by half compared to Example 1.

[0075] Input chemicals Component % (weight %) Oxalic acid dihydrate 17.44 Demineralized water 27.17 Fe(II) oxalate 22.04 50% H2O2 13.03 85% H3PO414.16 Lithium carbonate 4.59 Ethoxylated Lauryl Alcohol Surfactant 1.37

[0076] Oxalic acid was added to demineralized water in a stirred tank to form a suspended slurry. Iron(II) oxalate was then added to the stirred slurry. Hydrogen peroxide was dosed at a controlled rate while cooling the jacketed tank to maintain the tank contents at 70°C. A mixture of soluble iron(III) oxalate was formed as a coffee-colored solution with excess oxalic acid chelating agent present. The mixture was cooled to 50°C, and then phosphoric acid was added, changing the solution color to green. When the temperature of the tank contents reached 40°C, cooling was discontinued and lithium carbonate powder was dosed into the stirred tank, where it completely dissolved in approximately 5 minutes.

[0077] The solution was pumped into the feed tank of the spray dryer, where the ethoxylated lauryl alcohol surfactant was added at a reduced dosage and thoroughly dispersed using a tank mixer. The solution was spray-dried using a disk atomizer with a drying chamber inlet gas temperature of 300°C using a disk atomizer. Addition of ethoxylated lauryl alcohol surfactant at half the dosage of Example 1 provided a dry, free-flowing yellow powder and high product recovery, in contrast to experiments without surfactant, which produced a wet powder with approximately two-thirds of product loss due to the accumulation of sticky powder in the drying chamber. The dry, free-flowing powder was stored under a nitrogen atmosphere to prevent oxidation. The powder was heat-treated in a nitrogen-purged, mechanically fluidized reactor at 450°C for 45 minutes, producing an LFP with a crystallite size of approximately 50 nm and a phase purity of greater than 99%.

[0078] LFP was mixed with demineralized water to form a slurry with a solids content of 25% (m / m), and sucrose was added at an increased dosage of 4.8% of the LFP mass (vs. 4.2% in Example 1). The slurry was milled in a bead mill equipped with 0.5 mm beads for 80 minutes to reduce the LFP particle size to a D50 of 338 nm. The slurry was transferred to the feed tank of a spray dryer, where demineralized water was added to reduce the slurry to a solids content of 13% (m / m). The slurry was spray-dried using an air atomizing nozzle operating at a pressure of 4.0 bar, a drying chamber inlet gas temperature of 188°C, and an outlet temperature of 93°C. A free-flowing powder consisting of LFP agglomerates coated with sucrose was obtained.

[0079] The powder was placed in a graphite crucible in a pilot-scale tube furnace and dried under vacuum at 160°C for 60 minutes. After drying, the vacuum atmosphere was replaced with nitrogen gas (99.99%) and the furnace temperature was increased to 740°C over 60 minutes. The LFP was held under nitrogen and subjected to a 120-minute soak time at 740°C to convert the sucrose to carbon and sinter the LFP to a crystallite size of 96 nm. The furnace was allowed to cool to below 60°C over 12 hours before the LFP was removed from the tray and packaged in sealed foil bags under a dry atmosphere.

[0080] The LFP was subjected to physical, chemical, and electrochemical characterization, and the results are tabulated below. Physical and chemical properties indicated that it provided satisfactory electrode fabrication properties, and electrochemical testing confirmed a capacity of 158 mAh / g and 77% retention at a 5C charge / discharge rate. [Table 3] [Table 4]

[0081] Example 1C Lithium iron phosphate (LFP) was prepared on a laboratory scale using the raw material formulation shown below for a total mixed mass of 793 g.

[0082] Input chemicals Component % (weight %) Oxalic acid dihydrate 11.33 Demineralized water 53.78 Fe(II) oxalate 14.32 50% H2O28.38 85% H3PO49.20 Lithium carbonate 2.98 Ethoxylated Lauryl Alcohol Surfactant 3.78

[0083] Oxalic acid was added to demineralized water in a stirred beaker to form a suspended slurry. Iron(II) oxalate was then added to the stirred slurry. Hydrogen peroxide was dosed at a controlled rate while cooling using a water bath to maintain the beaker contents at (or below) 70°C. A mixture of soluble iron(III) oxalate was formed as a coffee-colored solution with excess oxalic acid chelating agent present. The mixture was cooled to 50°C, and then phosphoric acid was added, causing the solution color to change to green. Cooling was discontinued when the temperature of the beaker contents reached 40°C, and lithium carbonate powder was dosed into the stirred beaker and completely dissolved in approximately 5 minutes.

[0084] The solution was transferred to a spray dryer feed beaker, where an ethoxylated lauryl alcohol surfactant was added and thoroughly dispersed using a magnetic stirrer. The solution was spray dried using an air atomizer nozzle with an inlet gas temperature of the drying chamber of 160°C. The dried, free-flowing powder was stored under a dry atmosphere to prevent oxidation. The powder was heat-treated in a nitrogen-purged tube furnace at 450°C for 1.2 hours to produce an LFP with a crystallite size of approximately 45 nm and a phase purity of greater than 98%.

[0085] LFP was mixed with demineralized water to form a slurry with 20% (m / m) solids, and sucrose was added at a dosage of 5% of the LFP mass. The slurry was milled in a bead mill equipped with 1.0 mm beads for 120 minutes to reduce the LFP particle size to a D50 of 400 nm. The slurry was transferred to the feed beaker of a spray dryer, where demineralized water was added to reduce the slurry to 10-12% (m / m) solids. The slurry was spray-dried using an air atomizing nozzle operating at 6-7 bar pressure, a drying chamber inlet gas temperature of 160 °C, and an outlet temperature of 95 °C. A free-flowing powder consisting of sucrose-coated LFP agglomerates was obtained.

[0086] The powder was placed in a ceramic crucible in a laboratory-scale tube furnace and dried under vacuum at 150°C for 60 minutes. After drying, the vacuum atmosphere was replaced with nitrogen gas (99.99%) and the furnace temperature was increased to 700°C. The LFP was held under nitrogen and subjected to a 120-minute soak time at 700°C to convert the sucrose to carbon and sinter the LFP to a crystallite size of approximately 55 nm. The furnace was allowed to cool to below 60°C over 12 hours before the LFP was removed from the crucible and placed in a plastic bottle for testing.

[0087] The LFP was subjected to physical, chemical, and electrochemical characterization and the results are tabulated below: Electrochemical testing confirmed a capacity of over 155 mAh / g and a retention rate of over 75% at a charge / discharge rate of 5C. [Table 5] [Table 6]

[0088] Example 2 - Production of lithium iron phosphate using the slurry in step (a) The following general procedures were used in the examples:

[0089] This process is similar to that of Example 1, except for the precursor mixing step, which relies on finely grinding the iron precursor in a slurry with the other ingredients before spray drying, as opposed to complete dissolution of the iron precursor using oxalic acid and hydrogen peroxide. This change eliminates the need for oxalic acid or hydrogen peroxide, resulting in a significant reduction in chemical input costs. The process consists of the following steps:

[0090] (1) Preparation of precursor slurry mixture The process used for the preparation of the precursor slurry is as follows: Weigh out the required mass of raw materials for the batch, including demineralized water, iron(II) oxalate dihydrate, phosphoric acid, lithium carbonate, and ethoxylated lauryl alcohol surfactant. Transfer the demineralized water into the bead mill's supply tank and start the tank mixer. Add phosphoric acid to the bead mill feed tank while continuously mixing. Dosing lithium carbonate powder into the bead mill feed tank at a moderate rate and mixing continuously until the lithium carbonate powder is dissolved, while limiting foaming. Start the bead mill and the pump that circulates the solution from the supply tank to the bead mill, and establish stable circulation and grinding operation. • Begin adding iron(II) oxalate to the feed tank and continue dosing the entire amount of iron(II) oxalate at a rate that allows stable mill operation. • Demineralized water is added to the slurry as needed to control the viscosity of the mix to maintain good mix flow in the feed tank and consistent flow through the mill. Mill the precursor slurry for 60-90 minutes until the particle size is reduced to a D50 of 700 nm. Transfer the milled slurry to the feed tank of the spray dryer and start the tank mixer Add the ethoxylated lauryl alcohol surfactant to the yellow precursor slurry and continue stirring until thoroughly dispersed.

[0091] Steps (2) to (5) are the same as those described in Example 1 and do not need to be repeated.

[0092] This general procedure was used in the following examples:

[0093] Example 2A Lithium iron phosphate (LFP) was prepared at pilot plant scale using the raw material blend shown below, with a total blend weight of 115 kg. The blend excluded the oxalic acid dihydrate and hydrogen peroxide used in the processes of Examples 1A-1C.

[0094] Input chemicals Component % (weight %) Demineralized water 44.39 Fe(II) oxalate 28.96 85% H3PO418.61 Lithium carbonate 6.22 Ethoxylated Lauryl Alcohol Surfactant 1.81

[0095] Demineralized water was weighed into the bead mill's feed tank, and phosphoric acid was added while the solution was being stirred. Lithium carbonate was dosed into the phosphoric acid solution with continuous stirring, resulting in dissolution of the lithium carbonate and a moderate increase in the temperature of the mixture to 36°C without cooling. The bead mill was started, and Fe(II) oxalate was added to the bead mill's feed tank while the solution was circulated through the mill. The poorly soluble Fe(II) oxalate formed a suspended slurry, which was milled in a bead mill equipped with 0.5 mm beads for 60 minutes to reduce the particle size to a D50 of 730 nm. As milling progressed, demineralized water was added to manage the increase in viscosity to allow for effective mixing and milling, resulting in a final milled slurry containing 29% (m / m) solids.

[0096] The slurry was pumped into the spray dryer's feed tank, where an ethoxylated lauryl alcohol surfactant was added and thoroughly dispersed using a tank mixer. The addition of the surfactant further reduced the slurry's viscosity to a consistency suitable for spray drying. The solution was spray-dried using a disk atomizer with a drying chamber inlet gas temperature of 306°C. In addition to reducing the slurry's viscosity to a sprayable consistency, the surfactant resulted in a dry, free-flowing yellow powder and high product recovery. This contrasts with experiments without surfactant, which produced a damp powder with approximately two-thirds of the product lost due to the accumulation of sticky powder in the drying chamber. The dry, free-flowing powder was stored under a nitrogen atmosphere to prevent oxidation. The powder was heat-treated in a nitrogen-purged, mechanically fluidized reactor at 450°C for 60 minutes, producing an LFP with a crystallite size of approximately 50 nm and a phase purity of greater than 98%.

[0097] LFP was mixed with demineralized water to form a slurry with 20% (m / m) solids, and sucrose was added at a dosage of 4.5% of the LFP mass. The slurry was milled in a bead mill equipped with 0.5 mm beads for 120 minutes to reduce the LFP particle size to a D50 of 331 nm. The slurry was transferred to the feed tank of a spray dryer, where demineralized water was added to reduce the slurry to 13% (m / m) solids.

[0098] The slurry was spray dried using an air atomizing nozzle operating at a pressure of 4.4 bar, an inlet gas temperature of the drying chamber of 225° C., and an outlet temperature of 98° C. A free-flowing powder consisting of sucrose-coated LFP agglomerates was obtained.

[0099] The powder was placed in a graphite crucible in a pilot-scale tube furnace and dried under vacuum at 160°C for 60 minutes. After drying, the vacuum atmosphere was replaced with nitrogen gas (99.99%) and the furnace temperature was increased to 760°C over 60 minutes. The LFP was held under nitrogen and subjected to a 120-minute soak time at 760°C to convert the sucrose to carbon and sinter the LFP to a crystallite size of 99 nm. The furnace was allowed to cool to below 60°C over 12 hours before the LFP was removed from the tray and packaged in sealed foil bags under a dry atmosphere.

[0100] The LFP was subjected to physical, chemical, and electrochemical characterization, and the results are tabulated below. Physical and chemical properties indicated satisfactory electrode fabrication performance, and electrochemical testing confirmed a capacity of 159 mAh / g and 76% retention at a 5C charge / discharge rate. Therefore, comparable performance was achieved with reduced raw material amounts and therefore reduced material costs compared to the processes of Examples 1A-1C. [Table 7] [Table 8]

[0101] Example 2B Lithium iron phosphate (LFP) was prepared at pilot plant scale using the raw material blend shown below, with a total blend weight of 115 kg. The blend excluded the oxalic acid dihydrate and hydrogen peroxide used in the processes of Examples 1A-1C.

[0102] Input chemicals Component % (weight %) Demineralized water 44.39 Fe(II) oxalate 28.96 85% H3PO418.61 Lithium carbonate 6.22 Ethoxylated Lauryl Alcohol Surfactant 1.81

[0103] Demineralized water was weighed into the feed tank of the bead mill, and phosphoric acid was added while the solution was stirred. Lithium carbonate was dosed into the phosphoric acid solution with continuous stirring, resulting in dissolution of the lithium carbonate and a moderate increase in the temperature of the mixture to 36°C without cooling.

[0104] The bead mill was started and Fe(II) oxalate was added to the bead mill's feed tank while the solution was circulated through the mill. The poorly soluble Fe(II) oxalate formed a suspended slurry, which was milled in a bead mill equipped with 0.5 mm beads for 60 minutes to reduce the particle size to a D50 of 730 nm. As milling progressed, demineralized water was added to manage the increase in viscosity to allow for effective mixing and milling, resulting in a final milled slurry containing 29% (m / m) solids.

[0105] The slurry was pumped into the spray dryer's feed tank, where an ethoxylated lauryl alcohol surfactant was added and thoroughly dispersed using a tank mixer. The addition of the surfactant further reduced the slurry's viscosity to a consistency suitable for spray drying. The solution was spray-dried using a disk atomizer with a drying chamber inlet gas temperature of 306°C. In addition to reducing the slurry's viscosity to a sprayable consistency, the surfactant resulted in a dry, free-flowing yellow powder and high product recovery. This contrasts with experiments without surfactant, which produced a damp powder with approximately two-thirds of the product lost due to the accumulation of sticky powder in the drying chamber. The dry, free-flowing powder was stored under a nitrogen atmosphere to prevent oxidation. The powder was heat-treated in a nitrogen-purged, mechanically fluidized reactor at 450°C for 60 minutes, producing an LFP with a crystallite size of approximately 50 nm and a phase purity of greater than 98%.

[0106] LFP was mixed with demineralized water to form a slurry with 20% (m / m) solids, and glucose was added at a dosage of 4.7% of the LFP mass. The slurry was milled in a bead mill equipped with 0.5 mm beads for 110 minutes to reduce the LFP particle size to a D50 of 312 nm. The slurry was transferred to the feed tank of a spray dryer, where demineralized water was added to reduce the slurry to 13% (m / m) solids. The slurry was spray-dried using an air atomizing nozzle operating at a pressure of 4.2 bar, a drying chamber inlet gas temperature of 222 °C, and an outlet temperature of 95 °C. A free-flowing powder consisting of glucose-coated LFP agglomerates was obtained.

[0107] The powder was placed in a graphite crucible in a pilot-scale tube furnace and dried under vacuum at 160°C for 60 minutes. After drying, the vacuum atmosphere was replaced with nitrogen gas (99.99%) and the furnace temperature was increased to 728°C over 60 minutes. The LFP was held under nitrogen and subjected to a 120-minute soak time at 728°C to convert the glucose to carbon and sinter the LFP to a crystallite size of 106 nm. The furnace was allowed to cool to below 60°C over 12 hours before the LFP was removed from the tray and packaged in sealed foil bags under a dry atmosphere.

[0108] The LFP was subjected to physical, chemical, and electrochemical characterization, and the results are tabulated below. The physical and chemical properties indicated that it provided satisfactory electrode fabrication properties, and electrochemical testing confirmed a capacity of 160 mAh / g and 75% retention at a charge / discharge rate of 5 C. Thus, comparable performance was obtained to Example 3, which used glucose instead of sucrose as the carbon source, resulting in a reduced C% and a higher active material content in the product. [Table 9] [Table 10]

[0109] Example 2C Lithium iron phosphate (LFP) was prepared on a laboratory scale using the raw material formulation shown below, with a total mixed mass of 321 g. The mixture excluded the oxalic acid dihydrate and hydrogen peroxide used in the processes of Examples 1A-1C.

[0110] Input chemicals Component % (weight %) Demineralized water 70.0 Fe(II) oxalate 15.2 85% H3PO49.7 Lithium carbonate 3.1 Ethoxylated Lauryl Alcohol Surfactant 2.0

[0111] Demineralized water was weighed into a beaker, and phosphoric acid was added while stirring the solution. Lithium carbonate was added to the phosphoric acid solution with continuous stirring, resulting in dissolution of the lithium carbonate. Fe(II) oxalate was then added to the solution, resulting in a suspended slurry of sparingly soluble Fe(II) oxalate. The Fe(II) oxalate slurry was bead-milled in a bead mill equipped with 1.0 mm beads for 150 minutes to reduce the particle size to a D50 of approximately 700 nm. Demineralized water was added to obtain a final milled slurry containing 15% (m / m) solids.

[0112] The slurry was transferred to the spray dryer's feed beaker, where an ethoxylated lauryl alcohol surfactant was added and thoroughly dispersed using a magnetic stirrer. The solution was spray-dried using an air atomizing nozzle with a drying chamber inlet gas temperature of 160°C. In addition to reducing the slurry's viscosity to a sprayable consistency, the surfactant resulted in a dry, free-flowing yellow powder and high product recovery. The dried, free-flowing powder was stored under a dry atmosphere to prevent oxidation. The powder was heat-treated in a nitrogen-purged laboratory tube furnace at 450°C for 60 minutes to produce an LFP with a crystallite size of approximately 45 nm and a phase purity of greater than 98%.

[0113] LFP was mixed with demineralized water to form a slurry with 20% (m / m) solids, and sucrose was added at a dosage of 5.0% of the LFP mass. The slurry was milled in a bead mill equipped with 1.0 mm beads for 120 minutes to reduce the LFP particle size to a D50 of 400 nm. The slurry was transferred to the feed beaker of a spray dryer, where demineralized water was added to reduce the slurry to 10% (m / m) solids. The slurry was spray-dried using an air atomizing nozzle operating at 6-7 bar pressure, a drying chamber inlet gas temperature of 160 °C, and an outlet temperature of 95 °C. A free-flowing powder consisting of sucrose-coated LFP agglomerates was obtained.

[0114] The powder was placed in an alumina crucible in a laboratory-scale tube furnace and dried under vacuum at 150°C for 60 minutes. After drying, the vacuum atmosphere was replaced with nitrogen gas (99.99%) and the furnace temperature was increased to 700°C over 60 minutes. The LFP was held under nitrogen and subjected to a 120-minute soak time at 700°C to convert the sucrose to carbon and sinter the LFP to a crystallite size of 50 nm. The furnace was allowed to cool to below 60°C over 12 hours before the LFP was removed from the crucible and packaged in a sealed bottle for testing.

[0115] The LFP was subjected to physical, chemical, and electrochemical characterization, and the results are tabulated below. Electrochemical testing confirmed a capacity of over 155 mAh / g and a retention rate of over 75% at a charge / discharge rate of 5C. Thus, comparable performance was obtained with reduced raw material amounts and therefore reduced material costs compared to the process used in Examples 1A-1C. [Table 11] [Table 12]

[0116] Example 2D Lithium iron phosphate (LFP) was prepared at pilot plant scale using the raw material blend shown below, with a total blend mass of 115 kg. The blend excluded the oxalic acid dihydrate and hydrogen peroxide used in the processes of Examples 1A-1C. Compared to pilot plant Examples 2A and 2B, the ratio of H3PO4 and lithium carbonate to Fe(II) oxalate was increased, resulting in an LFP with a more tilted stoichiometry.

[0117] Input chemicals Component % (weight %) Demineralized water 44.26 Fe(II) oxalate 28.88 85% H3PO418.83 Lithium carbonate 6.22 LA9 surfactant 1.81

[0118] Demineralized water was weighed into the feed tank of the bead mill and the phosphoric acid was added while stirring the solution. Lithium carbonate was dosed into the phosphoric acid solution with continuous stirring, resulting in dissolution of the lithium carbonate and a moderate increase in the temperature of the mixture.

[0119] The bead mill was started and Fe(II) oxalate was added to the bead mill's feed tank while the solution was circulated through the mill. The poorly soluble Fe(II) oxalate formed a suspended slurry, which was milled in a bead mill equipped with 0.5 mm beads for 85 minutes to reduce the particle size to a D50 of 712 nm. As milling progressed, demineralized water was added to manage the increase in viscosity to allow for effective mixing and milling, resulting in a final milled slurry containing 33% (m / m) solids.

[0120] The slurry was pumped into the spray dryer's feed tank, where LA9 (ethoxylated lauryl alcohol) surfactant was added and thoroughly dispersed using a tank mixer. The addition of LA9 further reduced the slurry's viscosity to a consistency suitable for spray drying. The solution was spray-dried using a disk atomizer with a drying chamber inlet gas temperature of 300°C. In addition to reducing the slurry's viscosity to a sprayable consistency, LA9 resulted in a dry, free-flowing yellow powder and high product recovery. This contrasts with experiments without LA9, which produced a damp powder with approximately two-thirds of the product lost due to the accumulation of sticky powder in the drying chamber. The dry, free-flowing powder was stored under a nitrogen atmosphere to prevent oxidation. The powder was heat-treated in a nitrogen-purged, mechanically fluidized reactor at 450°C for 75 minutes, producing an LFP with a crystallite size of approximately 50 nm and a phase purity of greater than 98%.

[0121] LFP was mixed with demineralized water to form a slurry with 20% (m / m) solids, and sucrose was added at a dosage of 5.1% of the LFP mass. The slurry was milled in a bead mill equipped with 0.5 mm beads for 75 minutes to reduce the LFP particle size to a D50 of 281 nm. The slurry was transferred to the feed tank of a spray dryer, where demineralized water was added to reduce the slurry to 13% (m / m) solids. The slurry was spray-dried using an air atomizing nozzle operating at a pressure of 3.8 bar, a drying chamber inlet gas temperature of 186°C, and an outlet temperature of 94°C. A free-flowing powder consisting of sucrose-coated LFP agglomerates was obtained.

[0122] The powder was placed in a graphite crucible in a pilot-scale tube furnace and dried under vacuum at 160°C for 60 minutes. After drying, the vacuum atmosphere was replaced with nitrogen gas (99.99%) and the furnace temperature was increased to 760°C over 60 minutes. The LFP was held under nitrogen and subjected to a 120-minute soak time at 760°C to convert the sucrose to carbon and sinter the LFP to a crystallite size of 131 nm. The furnace was allowed to cool to below 60°C over 12 hours before the LFP was removed from the tray and packaged in sealed foil bags under a dry atmosphere.

[0123] The LFP was subjected to physical, chemical, and electrochemical characterization, and the results are tabulated below. Physical and chemical properties indicated satisfactory electrode fabrication properties, and electrochemical testing showed a specific capacity of 160.8 mAh / g at 0.1 C and 69% retention at a 5 C charge / discharge rate. Thus, improved specific capacity was obtained compared to Examples 2A-2B, which have a less slant stoichiometry. [Table 13] [Table 14]

[0124] Example 2E Lithium iron phosphate (LFP) was prepared at pilot plant scale using the raw material formulation shown below, which is the same formulation used in Example 2D, with a total blend mass of 115 kg. The blend excluded the oxalic acid dihydrate and hydrogen peroxide used in the processes of Examples 1A-1C. Compared to pilot plant Examples 2A and 2B, the ratio of H3PO4 and lithium carbonate to Fe(II) oxalate was increased, resulting in an LFP with a more tilted stoichiometry.

[0125] Input chemicals Component % (weight %) Demineralized water 44.26 Fe(II) oxalate 28.88 85% H3PO418.83 Lithium carbonate 6.22 LA9 surfactant 1.81

[0126] Demineralized water was weighed into the feed tank of the bead mill and the phosphoric acid was added while stirring the solution. Lithium carbonate was dosed into the phosphoric acid solution with continuous stirring, resulting in dissolution of the lithium carbonate and a moderate increase in the temperature of the mixture.

[0127] The bead mill was started and Fe(II) oxalate was added to the bead mill's feed tank while the solution was circulated through the mill. The poorly soluble Fe(II) oxalate formed a suspended slurry, which was milled in a bead mill equipped with 0.5 mm beads for 90 minutes to reduce the particle size to a D50 of 716 nm. As milling progressed, demineralized water was added to manage the increase in viscosity to allow for effective mixing and milling, resulting in a final milled slurry containing 30% (m / m) solids.

[0128] The slurry was pumped into the spray dryer's feed tank, where LA9 (ethoxylated lauryl alcohol) surfactant was added and thoroughly dispersed using a tank mixer. The addition of LA9 further reduced the slurry's viscosity to a consistency suitable for spray drying. The solution was spray-dried using a disk atomizer with a drying chamber inlet gas temperature of 302°C. In addition to reducing the slurry's viscosity to a sprayable consistency, LA9 resulted in a dry, free-flowing yellow powder and high product recovery. This contrasts with experiments without LA9, which produced a damp powder with approximately two-thirds of the product lost due to the accumulation of sticky powder in the drying chamber. The dry, free-flowing powder was stored under a nitrogen atmosphere to prevent oxidation. The powder was heat-treated in a nitrogen-purged, mechanically fluidized reactor at 450°C for 75 minutes, producing an LFP with a crystallite size of approximately 50 nm and a phase purity of greater than 98%.

[0129] LFP was mixed with demineralized water to form a slurry with 18% (m / m) solids, and sucrose was added at a dosage of 5.1% of the LFP mass. The slurry was milled in a bead mill equipped with 0.5 mm beads for 80 minutes to reduce the LFP particle size to a D50 of 227 nm. The slurry was transferred to the feed tank of a spray dryer, where demineralized water was added to reduce the slurry to 12% (m / m) solids. The slurry was spray-dried using an air atomizing nozzle operating at a pressure of 3.0 bar, a drying chamber inlet gas temperature of 199 °C, and an outlet temperature of 95 °C. A free-flowing powder consisting of sucrose-coated LFP agglomerates was obtained.

[0130] The powder was placed in a graphite crucible in a pilot-scale tube furnace and dried under vacuum at 160°C for 60 minutes. After drying, the vacuum atmosphere was replaced with nitrogen gas (99.99%) and the furnace temperature was increased to 727°C over 60 minutes. The LFP was held under nitrogen and subjected to a 120-minute soak time at 727°C to convert the sucrose to carbon and sinter the LFP to a crystallite size of 122 nm. The furnace was allowed to cool to below 60°C over 12 hours before the LFP was removed from the tray and packaged in sealed foil bags under a dry atmosphere.

[0131] The LFP was subjected to physical, chemical, and electrochemical characterization, and the results are tabulated below. Physical and chemical properties indicated satisfactory electrode fabrication properties, and electrochemical testing showed a specific capacity of 161.6 mAh / g at 0.1 C and 76% retention at a 5 C charge / discharge rate. Thus, improved specific capacity was obtained compared to Examples 2A-2B, which have a less slant stoichiometry. [Table 15] [Table 16]

[0132] Example 3A provides an example of low Mn (30%) with increased energy density vs. LFP. Lithium manganese iron phosphate (LMFP) was prepared on a laboratory scale using the raw material blend shown below, providing a nominal Mn:Fe ratio of 0.3:0.7 and a total blend mass of 465 g. The blend excluded the oxalic acid dihydrate and hydrogen peroxide used in the processes of Examples 1A-1C.

[0133] Input chemicals Component % (weight %) Demineralized water 64.5 Fe(II) oxalate 12.9 Manganese(II) oxalate 5.5 85% H3PO412.1 Lithium Carbonate 4.0 LA9 Surfactant 1.0

[0134] Demineralized water was weighed into a beaker, and phosphoric acid was added while stirring the solution. Lithium carbonate was added to the phosphoric acid solution with continuous stirring, resulting in dissolution of the lithium carbonate. Fe(II) oxalate and Mn(II) oxalate were then added to the solution, resulting in a suspended slurry of sparingly soluble Fe(II) oxalate and Mn(II) oxalate. The slurry was bead-milled in a bead mill equipped with 1.0 mm beads for 150 minutes to reduce the particle size to a D50 of approximately 700 nm. Demineralized water was added to obtain a final milled slurry containing 15% (m / m) solids.

[0135] The slurry was transferred to the spray dryer's feed beaker, where LA9 (ethoxylated lauryl alcohol) surfactant was added and thoroughly dispersed using a magnetic stirrer. The solution was spray-dried using an air atomizing nozzle with a drying chamber inlet gas temperature of 165°C. In addition to reducing the slurry's viscosity to a sprayable consistency, LA9 resulted in a dry, free-flowing yellow powder and high product recovery. The dried, free-flowing powder was stored under a dry atmosphere to prevent oxidation. The powder was heat-treated in a nitrogen-purged laboratory tube furnace at 450°C for 60 minutes to produce LMFP with a crystallite size of approximately 50 nm and a phase purity of greater than 98%.

[0136] LMFP was mixed with demineralized water to form a slurry with 20% (m / m) solids, and sucrose was added at a dosage of 6.0% of the LMFP mass. The slurry was milled in a bead mill equipped with 1.0 mm beads for 150 minutes to reduce the LMFP particle size to a D50 of 400 nm. The slurry was transferred to the feed beaker of a spray dryer, where demineralized water was added to reduce the slurry to 10% (m / m) solids. The slurry was spray-dried using an air atomizing nozzle operating at 6-7 bar pressure, a drying chamber inlet gas temperature of 165 °C, and an outlet temperature of 95 °C. A free-flowing powder consisting of sucrose-coated LMFP agglomerates was obtained.

[0137] The powder was placed in an alumina crucible in a laboratory-scale tube furnace and dried under vacuum at 150°C for 60 minutes. After drying, the vacuum atmosphere was replaced with nitrogen gas (99.99%) and the furnace temperature was increased to 700°C over 90 minutes. The LMFP was held under nitrogen and subjected to a 120-minute soak time at 700°C to convert the sucrose to carbon and sinter the LMFP to a crystallite size of 55 nm. The furnace was allowed to cool to below 60°C over 12 hours before the LMFP was removed from the crucible and packaged in a sealed bottle for testing.

[0138] The LMFPs were subjected to physical, chemical, and electrochemical characterization, and the results are tabulated below. Electrochemical testing confirmed a capacity of over 158 mAh / g and a retention rate of over 75% at a 5C charge / discharge rate. Due to the higher cell voltage provided by Mn compared to Fe, the similar specific capacity obtained for the LMFPs compared to the LFPs of the preceding examples resulted in an increase in the energy density of the batteries made with the LMFPs. Thus, increased energy density was obtained for the LMFPs produced by substituting manganese for a portion of the iron in the LFPs compared to the energy density of the manganese-free LFPs of Examples 1A-1C and 2A-2D. [Table 17] [Table 18]

[0139] Example 3B provides an example of high Mn (60%) with increased energy density vs. LFP. Lithium manganese iron phosphate (LMFP) was prepared on a laboratory scale using the raw material blend shown below, which provided a nominal Mn:Fe ratio of 0.6:0.4 for a total blend mass of 465 g. The blend excluded the oxalic acid dihydrate and hydrogen peroxide used in the processes of Examples 1A-1C.

[0140] Input chemicals Component % (weight %) Demineralized water 64.5 Fe(II) oxalate 7.3 Manganese(II) oxalate 11.0 85% H3PO412.1 Lithium Carbonate 4.0 LA9 Surfactant 1.0

[0141] Demineralized water was weighed into a beaker, and phosphoric acid was added while stirring the solution. Lithium carbonate was added to the phosphoric acid solution with continuous stirring, resulting in dissolution of the lithium carbonate. Fe(II) oxalate and Mn(II) oxalate were then added to the solution, resulting in a suspended slurry of sparingly soluble Fe(II) oxalate and Mn(II) oxalate. The slurry was bead-milled in a bead mill equipped with 1.0 mm beads for 150 minutes to reduce the particle size to a D50 of approximately 700 nm. Demineralized water was added to obtain a final milled slurry containing 15% (m / m) solids.

[0142] The slurry was transferred to the spray dryer's feed beaker, where LA9 (ethoxylated lauryl alcohol) surfactant was added and thoroughly dispersed using a magnetic stirrer. The solution was spray-dried using an air atomizing nozzle with a drying chamber inlet gas temperature of 165°C. In addition to reducing the slurry's viscosity to a sprayable consistency, LA9 resulted in a dry, free-flowing yellow powder and high product recovery. The dried, free-flowing powder was stored under a dry atmosphere to prevent oxidation. The powder was heat-treated in a nitrogen-purged laboratory tube furnace at 450°C for 60 minutes to produce LMFP with a crystallite size of approximately 50 nm and a phase purity of greater than 98%.

[0143] LMFP was mixed with demineralized water to form a slurry with 20% (m / m) solids, and sucrose was added at a dosage of 6.0% of the LMFP mass. The slurry was milled in a bead mill equipped with 1.0 mm beads for 150 minutes to reduce the LMFP particle size to a D50 of 400 nm. The slurry was transferred to the feed beaker of a spray dryer, where demineralized water was added to reduce the slurry to 10% (m / m) solids. The slurry was spray-dried using an air atomizing nozzle operating at 6-7 bar pressure, a drying chamber inlet gas temperature of 165 °C, and an outlet temperature of 95 °C. A free-flowing powder consisting of sucrose-coated LMFP agglomerates was obtained.

[0144] The powder was placed in an alumina crucible in a laboratory-scale tube furnace and dried under vacuum at 150°C for 60 minutes. After drying, the vacuum atmosphere was replaced with nitrogen gas (99.99%) and the furnace temperature was increased to 700°C over 90 minutes. The LMFP was held under nitrogen and subjected to a 120-minute soak time at 700°C to convert the sucrose to carbon and sinter the LMFP to a crystallite size of 50 nm. The furnace was allowed to cool to below 60°C over 12 hours before the LMFP was removed from the crucible and packaged in a sealed bottle for testing.

[0145] The LMFPs were subjected to physical, chemical, and electrochemical characterization, and the results are tabulated below. Electrochemical testing confirmed a capacity of over 155 mAh / g and a retention rate of over 75% at a 5C charge / discharge rate. Due to the higher cell voltage provided by Mn compared to Fe, the similar specific capacity obtained for the LMFPs compared to the LFPs of the preceding examples resulted in an increase in the energy density of the batteries made with the LMFPs. Thus, increased energy density was obtained for the LMFPs produced by substituting manganese for a portion of the iron in the LFPs compared to the energy density of the manganese-free LFPs of Examples 1A-1C and 2A-2D. [Table 19] [Table 20]

[0146] In this specification and claims (where present), the word "comprising" and its derivatives, including "comprises" and "comprise", include each of the listed integers but do not exclude the inclusion of one or more further integers.

[0147] Throughout this specification, references to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0148] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to the specific features shown or described, since the means described herein constitute preferred forms for carrying out the invention. The invention is therefore claimed in any of its forms or modifications, within the proper scope of the appended claims (if any), as appropriately interpreted by those skilled in the art.

Claims

1. Formula Li ｘ M １－ｚ D ｚ P.O. ４ wherein M is one or more transition metals and D represents one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements, and 0.8≦x≦1.2 and 0≦z≦0.2; a) forming a mixture having a liquid, a source of the one or more transition metals, a source of phosphorus, a source of lithium, and a surfactant, and optionally a source of D, wherein the mixture formed in step (a) comprises a slurry in which one or more of the sources of the one or more transition metals, the source of phosphorus, the source of lithium, or, if present, the source of D, is present as particulate matter; (i) Li:PO relative to the stoichiometry required to form said material ４ :(M+D) is in the range of 1.04-1.10:1.00-1.05:1; or (ii) the ratio of (Li + PO ４ ): (M + D) ratio is greater than 2.05, Li:PO ４ : (M + D) ratio is Li > PO ４ >(M+D); b) drying the mixture from step (a) to form particles or a powder; c) heat treating the particles or powder from step (b) to form the material; d) mixing the material from step (c) with a liquid containing a carbon precursor; e) spray drying the mixture from step (d) to form particles of the material coated with the carbon precursor; f) converting the carbon precursor into carbon; A method comprising:

2. 2. The method of claim 1, wherein M is one or more transition metals selected from Fe, Mn, Ni, Co, Cr, or V; or M is Fe; or M comprises Fe and one or more of Mn, Ni, Co, Cr, or V; or M comprises two or more of Fe, Mn, Ni, Co, Cr, or V.

3. 3. The method of claim 1 or 2, wherein the source of one or more transition metals is present as particulate matter.

4. The method according to any one of claims 1 to 3, wherein the particulate matter or the slurry is milled before drying.

5. The method of any one of claims 1 to 4, wherein the source of one or more transition metals comprises a source of iron or an iron-containing compound.

6. the source of phosphorus comprises a phosphorus-containing compound or acid, or phosphoric acid, or a lithium-containing phosphate, or an organic phosphate or other phosphate-containing compound; and / or 6. The method of any one of claims 1 to 5, wherein the source of lithium comprises one or more of lithium-containing carbonates, lithium-containing phosphates, lithium-containing hydroxides, mineral lithium salts, lithium-containing organic mineral salts, or metallic lithium or other lithium-containing compounds.

7. 7. The method of any one of claims 1 to 6, wherein the source of D comprises one or more water-soluble compounds containing D, or one or more water-insoluble compounds containing D (including oxides), or mixtures thereof.

8. (Li + PO ４ 8. The method according to claim 1, wherein the ratio of (M+D) is in the range of 2.07 to 2.

13.

9. the surfactant is present in an amount of from 0.05% to 10% by weight of the mixture, or from 1% to 4% by weight of the mixture, or from 1.4% to 2.8%; and / or the source of one or more transition metals comprises from 5% to 40% by weight of the mixture, or from 10% to 35% by weight of the mixture, or from 15% to 30% by weight of the mixture; and / or the source of phosphorus is present in an amount of from 5% to 30% by weight of the mixture, or from 5% to 25% by weight of the mixture, or from 9% to 20% by weight of the mixture; and / or 9. The method of any one of claims 1 to 8, wherein the source of lithium is present in an amount from 2% to 21% by weight of the mixture, or from 2% to 10% by weight of the mixture, or from 2.5% to 8% by weight of the mixture, or from 3% to 7% by weight of the mixture.

10. The method of any one of claims 1 to 9, wherein step (b) comprises a spray drying step.

11. 11. The method of claim 10, wherein step (b) is carried out using a spray dryer, and wherein the inlet gas temperature to the dryer has a temperature of from 150°C to 500°C, or from 175°C to 350°C, and the dryer outlet gas has a temperature of from 50°C to 150°C, or from 80°C to 120°C.

12. 12. A method according to any preceding claim, wherein the powder produced in step (b) is a precursor powder or precursor particulate material, and wherein the precursor powder or precursor particulate material is heat treated to produce particles of the material.

13. The method according to any one of claims 1 to 12, wherein the heat treatment in step (c) is carried out in an oxygen-free atmosphere, or in a nitrogen atmosphere, or in an inert atmosphere.

14. 14. A method according to any one of the preceding claims, wherein step (c) comprises passing the powder / particulate material from step (b) through an environment having a temperature of 400 to 600°C, or 450 to 500°C, or 450 to 480°C, for a period of 5 minutes to 6 hours, or 10 minutes to 3 hours, or 20 minutes to 2 hours, or 30 minutes to 1 hour, or 45 minutes.

15. A method according to any preceding claim, wherein the material formed in step (c) comprises particles formed as agglomerates of microcrystals.

16. 16. The method of any one of claims 1 to 15, wherein the liquid containing the carbon precursor comprises a solvent containing a dissolved carbon precursor, or the liquid containing the carbon precursor comprises an aqueous solution containing a dissolved carbon precursor.

17. 17. The method of any one of claims 1 to 16, wherein the material produced in step (c) is ground in the liquid containing the carbon precursor.

18. A method according to any one of claims 1 to 17, wherein the carbon precursor is converted to carbon in step (f) by drying and then heating in a non-reactive or inert atmosphere to carbonize the carbon precursor.