Manufacture of high purity fepo4 from elemental iron and lifepo4 formed therefrom

Abstract

Provided is an improved method for forming iron phosphate, particularly as a precursor to lithium iron phosphate, comprising: forming a solution comprising an excess of phosphoric acid and an elemental iron to form a mixture; reacting the phosphoric acid and the elemental iron of the mixture in a reductive atmosphere to form a first liquid phase comprising Fe2 + and PO4 3 -; treating the first liquid phase with an oxidizer to oxidize the Fe2 + to Fe3 + thereby forming a second liquid phase and a second solid phase; and drying the second solid phase wherein the second solid phase comprises FePO4.

Description

MANUFACTURE OF HIGH PURITY FePO4FROM ELEMENTAL IRON ANDLiFePO4FORMED THEREFROMCROSS-REFERENCE TO RELATED APPLICATIONS.

[0001] The present invention claims priority to pending U.S. ProvisionalApplication No. 63 / 663,850 filed June 25, 2024.BACKGROUND OF THE INVENTION

[0002] The present invention is related to improvements in the synthesis of iron phosphate (FePO4) and the formation of lithium iron phosphate (LiFePO4 or LFP) formed therefrom. More specifically, the present invention is related to the formation of iron phosphate from elemental iron and the formation of LFP therefrom.

[0003] Lithium-ion batteries are now used throughout society from small devices, such as cell phones and the like, to transportation platforms, such as passenger and package transportation vehicles, and medical devices. Due to the widespread use and acceptance of lithium-ion batteries the demand has increased exponentially. The rapidly growing demand for LFP, and a preferred precursor therefore which is iron phosphate, has caused a significant demand on sources of iron. Many current commercial processes for the formation of iron phosphate involve iron sulphate as an intermediate. While widely available, iron sulphate is difficult to use due, in part, to the generation of sulphate, as a salt or as sulfuric acid, as a by-product. Those in the art have spent a considerable effort on the formation of iron phosphate, or LFP directly, from sources of iron which do not require iron sulphate as an intermediate product.

[0004] One very promising approach is the direct formation of LFP from elemental metal or metal oxide in a process referred to as the One-Pot Process exemplified in US Pat. No. 11 ,677,077. The advantages of elemental iron as a feed stock would be easily appreciated by one of skill in the art. A disadvantage is the incorporation of metal impurities which are incorporated into the LFP wherein the amount and composition of impurities is a function of the iron source.

[0005] Solid state synthetic methods are also well known in the manufacture of iron phosphate and LFP. As with the One-Pot process, the level of metal impurities present in the iron source remain and appear in the finished iron phosphate or LFP.

[0006] The present invention provides an improvement in the art which allows for the manufacture of iron phosphate, and ultimately LFP, wherein typical impurities associated with elemental iron are excluded in the manufacturing process without the necessity of pre-purifying the iron feed-stock.SUMMARY OF THE INVENTION

[0007] It is an object of the invention to provide an improved process for the formation of iron phosphate and LFP therefrom.

[0008] It is another object of the invention to provide an improved process for the formation of iron phosphate and LFP therefrom wherein the purity of iron is increased, relative to total metal content, by the process thereby increasing the available sources of elemental iron.

[0009] A particular feature of the invention is the ability to form iron phosphate and LFP in a continuous process wherein the iron phosphate formed, and ultimatelyLFP, has less metal impurity than the starting iron source.

[0010] A particular advantage is the generation of purified metals which are isolated as the impurities from the iron source.

[0011] These and other advantages, as will be realized, are provided in a method for forming iron phosphate comprising: forming a solution comprising phosphoric acid and an iron source wherein the iron source comprises elemental iron wherein the phosphoric acid is in a molar excess relative to the elemental iron to form a mixture; reacting the phosphoric acid and the elemental iron of the mixture in a reductive atmosphere to form a first liquid phase comprising Fe2+and PCM3-; treating the first liquid phase with an oxidizer to oxidize the Fe2+to Fe3+thereby forming a second liquid phase and a second solid phase; and drying the second solid phase wherein the second solid phase comprises FePCU.

[0012] Yet another embodiment is provided in a method for forming lithium iron phosphate comprising: forming a solution comprising phosphoric acid and an iron source wherein the iron source comprises elemental iron wherein the phosphoric acid is in a molar excess relative to the elemental iron to form a mixture; reacting the phosphoric acid and elemental iron of the mixture in a reductive atmosphere to form a first liquid phase comprising Fe2+and PCM3-;treating the first liquid phase with an oxidizer to oxidize the Fe2+to Fe3+thereby forming a second liquid phase and a second solid phase; drying the second solid phase wherein the second solid phase comprises FePCU; and mixing the FePCM with a lithium source and a carbon source to form a LFP precursor mixture; and sintering the LFP precursor mixture to form LiFePCU.BRIEF DESCRIPTION OF DRAWINGS

[0013] Fig. 1 is a flow-chart representation of an embodiment of the invention.

[0014] Fig. 2 is a flow-chart representation of an embodiment of the invention.

[0015] Fig. 3 is a flow-chart representation of an embodiment of the invention.DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention is related to improvements in the manufacture of iron phosphate and LFP therefrom. More specifically, the present invention is related to improvements in the manufacture of iron phosphate and LFP from elemental iron comprising metal contamination. Even more specifically, the present invention is related to the continuous manufacture of iron phosphate and LFP wherein metal impurities are excluded as the process continues therefore allowing for the use of elemental iron with levels of impurity which would not be suitable for use in other processes.

[0017] The invention will be described with reference to the figures which are an integral, but non-limiting, part of the specification provided for clarity of the invention.Throughout the various figures similar elements will be numbered according.

[0018] An embodiment of the invention will be described with reference to Fig. 1 wherein the invention is illustrated schematically as a batch process in flow-chart form. In Fig. 1 the iron source is combined with a molar excess of phosphoric acid (H3PO4) in aqueous solution at 10 to form a mixture. The iron source preferably comprises primarily elemental iron with metal impurities.

[0019] The iron source can comprise up to 1 wt% impurities, more preferably up to 2000 ppm impurities, more preferably up to 1000 ppm impurities, more preferably up to 500 ppm, more preferably up to 200 ppm and more preferably up to 100 ppm. The process is advantageous with very low, even pure, iron source but has particular advantage when the iron comprises impurities. The impurities of particular concern includes the group of metals selected from the group consisting of aluminum, calcium, sodium, silicon, zinc, zirconium, potassium, magnesium, manganese, chromium, nickel, cobalt, copper and titanium. If the process will be used for the formation of LFP the impurities of particular concern are those that are detrimental to the electrical properties of LFP as determined by functionality as a lithium-ion cathode material. Impurities of particular concern in LFP are metals selected from the group consisting of manganese, chromium, nickel, cobalt and copper. Of particular concern in LFP is copper as an impurity.

[0020] The phosphoric acid is preferably in a molar excess relative to iron wherein the molar excess is at least 2.0:1 , preferably at least 3.0:1 , more preferably at least 4.0:1 , even more preferably 5.0:1 . Below about 2.0:1 the reaction does not occur. Above about 5.0:1 the reaction is not significantly enhanced and therefore the additionalphosphoric acid provides no added benefit. For the purposes of the present invention the molar excess is defined relative to an equimolar ratio of PCU3’ to Fe°.

[0021] With further reference to Fig. 1 , the mixture comprising an iron source and an excess of phosphoric acid is reacted at 12 in a reductive atmosphere wherein the reductive atmosphere preferably comprises an inert gas. While not limited to theory it is hypothesized that the H+of the phosphoric acid oxides the Fe° to Fe2+and the reductive atmosphere inhibits further oxidation to Fe3+. The reaction of the iron source and phosphoric acid is preferably at a temperature of no more than 100°C at ambient pressure or atmospheric pressure which is not otherwise altered. At or above about 100°C the water begins to evaporate which is highly undesirable and optionally requires condensors and the like. It is more preferable to react the iron source and phosphoric acid at no more than about 80°C to achieve adequate reaction times. Cooling the reaction may not be necessary depending on scale. The ability to manufacture iron phosphate or LFP at temperatures below about 100°C at ambient pressure is a significant advantage over the art and especially over the art relying on the hydrothermal process to form LFP which requires reaction in a high temperature and high pressure consistent with reaction in an autoclave.

[0022] Reaction of the mixture comprising an iron source and excess of phosphoric acid in reductive atmosphere, at 12, generates a first liquid phase comprising Fe2+, which is primarily stoichiometrically in a soluble form such as FeHPCM, Fe3(PO4)2, Fe(H2PO4)2 or mixtures of related soluble compounds in water. Many of the undesirable impurity metals do not readily oxidize under the reaction conditions andtherefore a soluble salt, such as a metal phosphate, is not formed. The impurity metals or most concern for LFP; particularly copper, titanium, nickel, cobalt and manganese; remain as a first solid phase wherein the first solid phase is depleted of iron relative to the iron source or remain in the liquid phase with subsequent oxidation of iron. The first liquid phase and first solid phase are separated in a first separation step at 14 resulting in the first liquid phase at 16 and the first solid phase at 18. The first solid phase can be discarded or the metal impurities contained therein can be further purified, in a process which extends beyond the current invention, to provide purified metals of value for subsequent use.

[0023] With further reference to Fig. 1 , the first liquid phase is treated with an oxidation source at 20 wherein the iron is oxidized to Fe3+and precipitates as a second solid phase resulting in a second liquid phase. The second solid phase is a pink solid characterized by x-ray diffraction to be primarily in the form of FePO42H2O. Any solubilized impurity metal remains in the second liquid phase which further increases the iron content of the total metals composition in the second solid phase relative to the iron source. The result of oxidation is a second liquid phase, which is depleted of iron relative to the first liquid phase, and a second solid phase which is primarily an Fe3+salt, and primarily FePO42H2O, as a precipitate.

[0024] The second liquid phase and second solid phase are separated in a second separation step at 22 resulting in an excluded liquid phase at 24 comprising excess phosphate ion, PO4’3and excess acid. The excluded liquid phase can be discarded at 26 or the excluded liquid phase can be optionally treated at 28 to adjustpH, filtered to remove impurities or otherwise treated and recycled as a supplemental phosphoric acid feed stock. The second solid phase, 29, is optionally, and preferably, washed with deionized water at 30 followed by a third separation step 32 wherein the wash liquid phase 34 can be discarded at 35 or returned to the aqueous solution with or without treatment at 36. The third solid phase is recovered at 38 and optionally, but preferably dried at 40, to form purified FePCU at 42.

[0025] An embodiment of the invention will be described with reference to Fig. 2 wherein the invention is illustrated schematically as a near continuous process in flowchart form. In Fig. 2 the iron source is combined with a molar excess of phosphoric acid (H3PO4) in aqueous solution at 110 to form the mixture.

[0026] The mixture comprising the iron source and excess of phosphoric acid is reacted at 112 in a reductive atmosphere wherein the reductive atmosphere preferably comprises an inert gas. The reaction of the iron source and phosphoric acid is preferably at a temperature of no more than 100°C at ambient pressure.

[0027] Reaction of the mixture comprising the iron source and excess of phosphoric acid in reductive atmosphere, at 112, generates the first liquid phase comprising Fe2+, which is primarily stoichiometrically in the soluble form of Fe3(PO4)2, in water. Unreacted metals, including a portion of the iron, remain as a first solid phase. A portion of the liquid can be continuously removed at 114 by a liquid removal step forming the first liquid phase at 116 while the unreacted solid phase and retained liquid remains.

[0028] With further reference to Fig. 2, the first liquid phase is treated with an oxidation source at 120 wherein the iron is oxidized to Fe3+which precipitates as the third solid phase at 129 resulting in the excluded liquid phase. The excluded liquid phase is removed by liquid removal step at 122 wherein the excluded liquid phase is discarded at 126 or optionally, and preferably, treated at 128 to adjust pH, filtered to remove impurities or otherwise and recycled as a supplemental phosphoric acid feed stock. The third solid phase is optionally, and preferably washed with deionized water at 130 followed by a third separation step 132 wherein the wash liquid phase 134 can be discarded or returned to the mixture with or without treatment at 136. The third solid phase is recovered at 138 and optionally, but preferably dried at 140, to form purified FePO4 at 142.

[0029] An embodiment will be described relative to Fig. 3. Iron phosphate, in the form of FePCU is provided at 50. The FePCU is preferably the purified FePCMfrom the inventive process discussed herein. In an embodiment dry FePCM can combined with a lithium source and a carbon source to form a solid state mixture at 52. The solid state mixture is then fired at 54 to form LiFePCU at 56. In another embodiment the FePCU can combined with a lithium source and a carbon source in an precursor aqueous solution at 58. The precursor aqueous solution is dried at 60, and fired at 54 to form LiFePCM at 56.

[0030] A particular feature of the present invention is the exclusion of impurities by the sequential solubilization of and precipitation of specified iron salts. The process provides a FePCU wherein the level of impurities are decreased, relative to the ironsource, by at least 50%. By way of non-limiting example, presented for clarity only, an iron source comprising 2000 ppm impurity metal and 998,000 ppm iron, after processing would decrease the impurity metal by at least 50% resulting in no more than 1000 ppm impurity metal and at least 999,000 ppm iron. More preferably the level of impurities are decreased, relative to the iron source, by at least 60%, even more preferably at least 75% and most preferably at least 95%. Copper is a particularly detrimental impurity. The process provides a FePCM wherein the level of copper impurity is decreased, relative to the iron source, by at least 50%, more preferably at least 60%, even more preferably at least 75% and most preferably at least 95%

[0031] The process is described herein particularly for the formation of lithium iron phosphate, for convenience, with the understanding that iron can be replaced on an equal molar basis with nickel, manganese, cobalt, or combinations thereof as a substitutional additive to achieve, by the same process, an olivine lithium metal phosphate preferable comprising carbon, preferably as a coating, wherein the lithium metal phosphate or LFP has the general formula:LiFexNiaMnyCozPO4 wherein x + a + y + z = 1 wherein:0 < x < 1 more preferably 0.5 < x < 1 and most preferably 0.9 < x < 1 ;0 < y < 1 more preferably 0 < y < 0.5;0 < z < 1 more preferably 0 < z < 0.5; and0 < a < 0.1.

[0032] As noted throughout, the process is effective at decreasing impurity metals such as nickel, manganese and cobalt. When substitutional additives are intentionally to be included they can be added, preferably equimolar with phosphate, prior to drying to form the purified FePCU or alternatively, to the purified FePCM in concert with the combination with the lithium source and carbon source to form LFP.

[0033] Carbon, preferably as a coating, is desirable to obtain good electrochemical performance such as electrical conductivity, tap density, lithium ion diffusion, optimum particle size and phase purity. Carbon content also controls crystal growth of the LFP during calcination with particle size being inversely correlated to carbon content. The tap density is also inversely correlated to carbon content.Furthermore, at high carbon content impurities appear due to the reduction of iron. If the carbon content is insufficient impurities are formed due to the oxidation of iron. A final carbon content of at least 1 wt% to no more than 3 wt% is preferred to achieve optimum conductivity with sufficient tap density and particle size. Most preferably the carbon content is at least 1 .3 wt% to no more than 2.5 wt% with 1 .4 to 1 .7 wt% being most preferred. Above about 2 wt% carbon content the electrical conductivity is not appreciably improved and as the carbon coating thickness increases the lithium ion diffusion rate can be compromised. For these reasons, and to maximize tap density, it is preferable to limit carbon content to no more than approximately 2 wt% and more preferably no more than approximately 1 .7 wt%.

[0034] The oxidizer used to oxidize the iron from Fe2+to Fe3+is not particularly limited herein with the proviso that the by-product of oxidation does not includedetrimental properties. Organic oxidizers are most preferred since any carbon byproduct will be removed during subsequent calcining or firing. Particularly preferred oxidizers include gases which are bubbled through the solution such as oxygen, particularly from air, or ozone. Peroxides, particularly hydrogen peroxide, and other chemical oxidizers are exemplary for demonstration of the invention. Electrochemical oxidation techniques can be employed but are less desirable due to the cost associated therewith. Hydrogen peroxide is a particularly suitable oxidizer due to ready availability, cost and effectiveness and advantageous decomposition products.

[0035] The lithium source is not particularly limited herein and is consistent with those currently used in the art of LFP production. Lithium carbonate, lithium oxalates and lithium hydroxide are most preferred.

[0036] The carbon source is not particularly limited herein and is consistent with those currently used in the art for LFP production. Particularly preferred carbon sources are sugars, organic acids, particularly carboxylic acids, and more particularly dicarboxylic acids or tri-carboxylic acids. Di- and tri-carboxyl ic acids with less than about 10, preferably alkyl, carbon atoms are most preferred. Particularly preferred acids are selected from the group consisting of citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioc acid, dodecanedioc acid, isocitric acid, aconitic acid, propane-1 ,2,3- tricarboxylic acid and sucrose. Citric acid and oxalic acid are preferred due to their low cost and wide spread availability. Particularly suitable carbon sources include oxalic acid, citric acid or polyvinyl acid with oxalic acid or a mixture of citric and oxalic acidbeing particularly suitable. Oxalic acid improves handling properties of reaction slurry. The reaction without oxalic acid tends to have insufficient carbon after firing. The reaction slurry without oxalic acid may become thick and viscous which may impact drying of the material. Polymers such as polyethylene derivatives and polyvinyl alcohol are also suitable carbon sources. Organic acids are preferred with citric acid monohydrate (C6H8O7-H2O) and oxalic acid dihydrate (H2C2O4-2H2O) being particularly preferred. Particularly preferred sugars include glucose and lactose.

[0037] A particularly suitable drying method for demonstration of the invention incorporates a heated drum dryer comprising a heated drum, preferably an internally heated drum, with an alternate heat source such as infrared, laser heat or UV heater external to the drum. The alternate heat source spot heats the material on the surface opposite the drum to change properties or cause a reaction at a certain material dryness.

[0038] Thin film drying can be accomplished as a batch process by drying the product with conduction from a surface with a temperature of about 150-250°C. The material remains affixed to the surface for a time of about a ms to seconds before being scraped off the surface. This allows the material to become crystalline and not sticky after drying. In this process, additional waters of hydration are removed and some partial reactions, such as oxalate decompositions and iron phosphate allotrope conversions, may occur. Drum drying is a continuous variation of thin film drying with similar behavior.

[0039] Evaporative drying in a tray results in similar behavior to the thin film drying methods. The slurry is dried in a reactor on a beaker while mixing at about 90°C until “muddy” then the mud is transferred to a drying convection oven overnight at about 90°C. The crystallinity is similar to the thin film drying, based on X-ray Diffraction (XRD), and the product behavior has similar electrochemical properties. This low temperature crystallinity indicates that the crystallinity is formed over time at about 90°C temperature.

[0040] Spray drying into a relatively low temperature drying air atmosphere results in a powdered material. While not bound by theory, it is hypothesized that staying below the glass transition temperature Tgof some of the components of the mixture suitable powder can be obtained. An inlet temperature of about 150-180°C and outlet temperature of about 110-130°C is suitable for demonstration of the invention.

[0041] The dried powder comprising metal phosphate, lithium source and carbon source is fired to obtain carbon coated LFP. A calcining temperature of 580-700°C under inert gas is preferred. Above about 740°C FesP impurity can be observed. Firing, or calcining, of the powder at about 600°C, preferably for 1 -10 hours and optionally under N2(g) is exemplary for demonstrating the invention. Below about 1 hour calcining may be incomplete. Beyond about 10 hours the phosphate begins to degrade. A calcining time of about 4 hours to about 10 hours is preferable. It is preferable that the inert gas comprise less than 0.01 wt% oxygen.

[0042] The reductive atmosphere is preferably an inert gas. Particularly preferred are nitrogen or noble gases such as helium, neon or argon with less than 0.01 wt% oxygen. Nitrogen gas, N2, is particularly preferred due to cost and availability.

[0043] The separation steps wherein solid and liquid are separated into two components is not particularly limited herein. Filtration, centrifugation, sedimentation, hydrocyclone based techniques, venrturi based techniques, classifers and flotation techniques are most preferable due to the wide spread use in industry and simplicity. For the purposes of the instant invention separation steps refer to those processes wherein the solid and liquid are separated resulting in an isolated solid and separate liquid with the understanding the that isolated solid may comprise some waters of hydration but are otherwise separated from the liquid.

[0044] For the purposes of the instant invention liquid removal steps refers to those steps which remove at least a portion of the liquid, preferably containing solubilized iron salts, and most preferably as Fe3(PO4)2 which may be hydrated, with a portion of the liquid remaining. Particularly preferred liquid removal steps are those conventionally employed in a continuous flow process including decanting, overflowing, aliquot extraction, pumping, etc.

[0045] Throughout the description a stoichiometric amount refers to the addition of a reactant in an amount sufficient to form the resulting product in the proper stoichiometry within experimental error. A stoichiometric amount, as defined herein, is at least within 5 mole% of the theoretical stoichiometric equivalent desired and preferably within 1 mole % of the theoretical stoichiometric amount desired. By way of example a stoichiometric equivalent of lithium and phosphate would preferably have a molar ratio of lithium to phosphate from 0.95:1 to 1.05:1 and preferably from 0.99:1 to 1.01 :1. Example 1 :

[0046] FePO4 2H2O was manufactured on a lab scale using the inventive batch process. The phosphoric acid / iron ratio was about 4:1 and hydrogen peroxide was used as the oxidizer. The iron source was determined to have the selected impurities of Co, Cr, Cu and Ni listed in Table 1 , in PPM, which was reduced as also listed in Table 1.Table 1 :

[0047] The example presented in Table 1 demonstrates advantages of the invention.

[0048] The invention has been described with reference to preferred embodiments without limit thereto. One of skill in the art would realize additional embodiments which are described and set forth in the claims appended hereto.

Claims

Claims1 . A method for forming iron phosphate comprising: forming a solution comprising phosphoric acid and an iron source wherein said iron source comprises elemental iron and wherein said phosphoric acid is in a molar excess relative to said elemental iron to form a mixture; reacting said phosphoric acid and said elemental iron of said mixture in a reductive atmosphere to form a first liquid phase comprising Fe2+and PO43-; treating said first liquid phase with an oxidizer to oxidize said Fe2+to Fe3+thereby forming a second liquid phase and a second solid phase; and drying said second solid phase wherein said second solid phase comprises FePO4.

2. The method for forming iron phosphate of claim 1 wherein said molar excess is at least 2.0:1 .

3. The method for forming iron phosphate of claim 2 wherein said molar excess is at least 3.0:1 .

4. The method for forming iron phosphate of claim 3 wherein said molar excess is at least 4.0:1 .

5. The method for forming iron phosphate of claim 4 wherein said molar excess is at least 5.0:1 .

6. The method for forming iron phosphate of claim 1 wherein said reacting is at a temperature of no more than 100°C.

7. The method for forming iron phosphate of claim 1 wherein said reacting is at ambient pressure.

8. The method for forming iron phosphate of claim 1 wherein said reductive atmosphere comprises nitrogen or a noble gas.

9. The method for forming iron phosphate of claim 1 wherein said reacting said phosphoric acid and said element iron forms a first solid phase.

10. The method for forming iron phosphate of claim 9 further comprising separating said first liquid phase from said first solid phase.

11. The method for forming iron phosphate of claim 10 wherein said separating said first liquid phase from said first solid phase is selected from separation and liquid removal.

12. The method for forming iron phosphate of claim 11 wherein said separating is selected from the group consisting of filtration and centrifugation, flotation, classification, gravity sedimentation.

13. The method for forming iron phosphate of claim 11 wherein said liquid removal is selected from the group consisting of decanting, overflowing, aliquot removal and pumping.

14. The method for forming iron phosphate of claim 1 further comprising separating said second liquid phase from said second solid phase.

15. The method for forming iron phosphate of claim 14 wherein said separating said second liquid phase from said second solid phase is selected from separation and liquid removal.

16. The method for forming iron phosphate of claim 15 wherein said separating is selected from the group consisting of filtration and centrifugation.

17. The method for forming iron phosphate of claim 15 wherein said liquid removal is selected from the group consisting of decanting, overflowing, aliquot removal and pumping.

18. The method for forming iron phosphate of claim 1 wherein said iron source comprises impurities.

19. The method for forming iron phosphate of claim 18 wherein said iron source comprises up to 1 wt% of said impurities.

20. The method for forming iron phosphate of claim 19 wherein said iron source comprises up to 2000 ppm of said impurities.21 . The method for forming iron phosphate of claim 20 wherein said iron source comprises up to 1000 ppm of said impurities.

22. The method for forming iron phosphate of claim 21 wherein said iron source comprises up to 500 ppm of said impurities.

23. The method for forming iron phosphate of claim 22 wherein said iron source comprises up to 200 ppm of said impurities.

24. The method for forming iron phosphate of claim 23 wherein said iron source comprises up to 100 ppm of said impurities.

25. The method for forming iron phosphate of claim 18 wherein said impurities are selected from the group consisting of group consisting of aluminum, calcium,sodium, silicon, zinc, zirconium, potassium, magnesium, manganese, chromium, nickel, cobalt, copper and titanium.

26. The method for forming iron phosphate of claim 25 wherein said impurities are selected from the group consisting of group consisting of manganese, chromium, nickel, cobalt and copper.

27. The method for forming iron phosphate of claim 26 wherein said impurities is copper.

28. The method for forming iron phosphate of claim 18 wherein said impurities are in a first concentration relative to said elemental iron.

29. The method for forming iron phosphate of claim 28 wherein impurities in said second solid phase are in a second concentration relative to said elemental iron and said second concentration is lower than said first concentration.

30. The method for forming iron phosphate of claim 29 wherein said second concentration is at least 50% lower than said first concentration.31 . The method for forming iron phosphate of claim 30 wherein said second concentration is at least 60% lower than said first concentration.

32. The method for forming iron phosphate of claim 31 wherein said second concentration is at least 75% lower than said first concentration.

33. The method for forming iron phosphate of claim 32 wherein said second concentration is at least 95% lower than said first concentration.

34. The method for forming iron phosphate of claim 1 comprising adding said second liquid phase to said mixture.

35. The method for forming iron phosphate of claim 1 wherein said oxidizer is selected from the group consisting of hydrogen peroxide, oxygen and ozone.

36. A method for forming lithium iron phosphate comprising: forming a solution comprising phosphoric acid and an iron source wherein said iron source comprises elemental iron wherein said phosphoric acid is in a molar excess relative to said elemental iron to form a mixture; reacting said phosphoric acid and said elemental iron of said mixture in a reductive atmosphere to form a first liquid phase comprising Fe2+and PO43-; treating said first liquid phase with an oxidizer to oxidize said Fe2+to Fe3+thereby forming a second liquid phase and a second solid phase; drying said second solid phase wherein said second solid phase comprises FePCM; and mixing said FePCM with a lithium source and a carbon source to form a LFP precursor mixture; and sintering said LFP precursor mixture to form LiFePCM.

37. The method for forming lithium iron phosphate of claim 36 wherein said lithium source is selected from the group consisting of lithium carbonate, lithium oxalates and lithium hydroxide.

38. The method for forming lithium iron phosphate of claim 36 wherein said carbon source is a sugar or an organic acid.

39. The method for forming lithium iron phosphate of claim 36 further comprising addition of at least one of Co, Mn or Ni to said LFP precursor mixture.

40. The method for forming lithium iron phosphate of claim 36 wherein said lithium iron phosphate has the general formula:LiFexNiaMnyCozPO4 wherein x + a + y + z = 1 wherein:0 < x < 1 ;0 < y < 1 ;0 < z <1 ; and0 < a < 0.1 .41 . The method for forming lithium iron phosphate of claim 36 wherein said molar excess is at least 2.0:1.

42. The method for forming lithium iron phosphate of claim 41 wherein said molar excess is at least 3.0:1.

43. The method for forming lithium iron phosphate of claim 42 wherein said molar excess is at least 4.0:1.

44. The method for forming lithium iron phosphate of claim 43 wherein said molar excess is at least 5.0:1.

45. The method for forming lithium iron phosphate of claim 36 wherein said reacting is at a temperature of no more than 100°C.

46. The method for forming lithium iron phosphate of claim 36 wherein said reacting is at ambient pressure.

47. The method for forming lithium iron phosphate of claim 36 wherein said reductive atmosphere comprises nitrogen or a noble gas.

48. The method for forming lithium iron phosphate of claim 36 wherein said reacting said phosphoric acid and said element iron forms a first solid phase.

49. The method for forming lithium iron phosphate of claim 48 further comprising separating said first liquid phase from said first solid phase.

50. The method for forming lithium iron phosphate of claim 49 wherein said separating said first liquid phase from said first solid phase is selected from separation and liquid removal.51 . The method for forming lithium iron phosphate of claim 50 wherein said separating is selected from the group consisting of filtration and centrifugation.

52. The method for forming lithium iron phosphate of claim 50 wherein said liquid removal is selected from the group consisting of decanting, overflowing, aliquot removal and pumping.

53. The method for forming lithium iron phosphate of claim 30 further comprising separating said second liquid phase from said second solid phase.

54. The method for forming lithium iron phosphate of claim 53 wherein said separating said second liquid phase from said second solid phase is selected from separation and liquid removal.

55. The method for forming lithium iron phosphate of claim 54 wherein said separating is selected from the group consisting of filtration and centrifugation.

56. The method for forming lithium iron phosphate of claim 54 wherein said liquid removal is selected from the group consisting of decanting, overflowing, aliquot removal and pumping.

57. The method for forming lithium iron phosphate of claim 36 wherein said iron source comprises impurities.

58. The method for forming lithium iron phosphate of claim 57 wherein said iron source comprises up to 1 wt% of said impurities.

59. The method for forming lithium iron phosphate of claim 58 wherein said iron source comprises up to 2000 ppm of said impurities.

60. The method for forming lithium iron phosphate of claim 59 wherein said iron source comprises up to 1000 ppm of said impurities.61 . The method for forming lithium iron phosphate of claim 60 wherein said iron source comprises up to 500 ppm of said impurities.

62. The method for forming lithium iron phosphate of claim 61 wherein said iron source comprises up to 200 ppm of said impurities.

63. The method for forming lithium iron phosphate of claim 62 wherein said iron source comprises up to 100 ppm of said impurities.

64. The method for forming lithium iron phosphate of claim 58 wherein said impurities are selected from the group consisting of group consisting of aluminum, calcium, sodium, silicon, zinc, zirconium, potassium, magnesium, manganese, chromium, nickel, cobalt, copper and titanium.

65. The method for forming lithium iron phosphate of claim 64 wherein said impurities are selected from the group consisting of group consisting of manganese, chromium, nickel, cobalt and copper.

66. The method for forming lithium iron phosphate of claim 65 wherein said impurities is copper.

67. The method for forming lithium iron phosphate of claim 49 wherein said impurities are in a first concentration relative to said elemental iron.

68. The method for forming lithium iron phosphate of claim 67 wherein impurities in said second solid phase are in a second concentration relative to said elemental iron and said second concentration is lower than said first concentration.

69. The method for forming lithium iron phosphate of claim 68 wherein said second concentration is at least 50% lower than said first concentration.

70. The method for forming lithium iron phosphate of claim 69 wherein said second concentration is at least 60% lower than said first concentration.71 . The method for forming lithium iron phosphate of claim 70 wherein said second concentration is at least 75% lower than said first concentration.

72. The method for forming lithium iron phosphate of claim 71 wherein said second concentration is at least 95% lower than said first concentration.

73. The method for forming lithium iron phosphate of claim 36 comprising adding said second liquid phase to said mixture.

74. The method for forming lithium iron phosphate of claim 36 wherein said oxidizer is selected from the group consisting of hydrogen peroxide, oxygen and ozone.

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