WO2009003093A1 - Metal phosphate compounds and batteries containing the same - Google Patents

Abstract

A method includes combining a lithium source, a phosphorus source, and an iron source into an aqueous solution, forming LiFePO4 from the solution, and forming an electrode including the LiFePO4. The LiFePO4.has less than approximately 15 % by weight of carbon.

Description

METAL PHOSPHATE COMPOUNDS AND BATTERIES CONTAINING THE SAME

CLAIM OF PRIORITY

This application claims priority to U.S. Provisional Patent Application 60/937,197, filed on June 26, 2007, and entitled "LiFePO₄", hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to metal phosphate compounds and doped metal phosphate compounds that can be used as, for example, electrochemically active electrode materials in batteries, including lithium-ion batteries.

BACKGROUND

The proliferation of portable electronic devices that demand high energy and power, such as laptop computers, cell phones and music players, and the demand for high energy power sources for hybrid electric vehicles, have spurred the demand for low cost, high energy, high power and safe batteries, such as lithium-ion batteries. These batteries can include electrodes containing an electrochemically active material having a crystallographic structure that allows reversible intercalation and de- intercalation of ions, such as lithium ions. Examples of such electrochemically active materials include LiCoO₂, LiNiO₂, LiCθi__x Ni_xO₂ and LiCoo.33Mno.33 Nio.33θ₂, lithium metal phosphates (such as LiFePO₄), and lithium mixed metal phosphates. LiFePO₄, for example, has been shown to have good energy capacity, low toxicity, outstanding cyclability, outstanding safety and low cost.

SUMMARY

In one aspect, the invention features a method including combining a lithium source, a phosphorus source, and an iron source into an aqueous solution; forming LiFePO₄ from the solution, the LiFePO₄ having less than approximately 15% by weight of carbon; and forming an electrode comprising the LiFePO₄.

In another aspect, the invention features a method, including forming a precursor comprising lithium, iron, phosphorus and an ammonium moiety; forming LiFePO₄ from the precursor; and forming an electrode comprising the LiFePO₄.

Embodiments may include one or more of the following features. The LiFePO₄ includes from approximately 1% by weight to approximately 15% by weight of carbon. The LiFePO₄ has an average crystallite size of less than approximately 100 nm. The LiFePO₄ has a DC electrical conductivity of equal to or greater than approximately I X lO^"9 S/cm (IHz). The lithium source includes a material selected from the group consisting of lithium hydroxide, lithium carbonate, lithium benzoate, and lithium acetate. The phosphorus source includes a phosphorus-containing chelation agent, such as editronic acid or iminobis(methyl-phosphonic acid). The iron source includes a material selected from the group consisting of iron oxide and iron carboxylate. The iron source includes a material selected from the group consisting of ferric oxalate, ferric ammonium oxalate, ferrous oxalate, hydrated iron oxide, iron ammonium carboxylate, and ferric oxyhydroxide. The method further includes combining in the aqueous solution an oxidizing agent capable of oxidizing the iron source, e.g., a ferrous iron source. The oxidizing agent includes hydrogen peroxide or ozone. The method further includes combining in the aqueous solution a carboxylic acid. The method further includes combining in the aqueous solution a metal source different from the lithium source and the iron source. The metal source includes niobium, zirconium, or titanium. Forming the LiFePO₄ includes forming a precursor from the aqueous solution (e.g., by drying or heating the solution), and heating the precursor. The aqueous solution is substantially free of a nitrate ion or a citrate ion. The method further includes using the electrode to make a lithium ion battery. Forming the LiFePO₄ is substantially free of mechanical mixing, such as milling to provide intimate mixing and particle size reduction.

Embodiments may include one or more of the following advantages. LiFePO₄ can be produced with crystallites less than 100 nm (e.g., less than

50nm) size; with low carbon content (e.g., less than approximately 15% by weight), which can be a problem associated with excessively high carbon content associated with using citrate precursors; and/or without exothermic reactivity, which can be a problem associated with using nitrate precursors. In some embodiments, reducing carbon content can be achieved by using a carboxylic acid anion that leaves less carbon in the LiFePO₄ product. The method can be readily controlled to adjust the amount of carbon in the LiFePO₄, as well as its electrical conductivity and crystallite size.

The LiFePO₄ can be substantially free of sulfur and/or a halide. All carbon contents provided herein are percentages by weight. As used herein, "substantially free" means less than approximately 5% by weight (e.g., less than approximately 3% by weight, or less than approximately 2% by weight).

An electrochemical cell can be a primary cell or a secondary cell. Primary electrochemical cells are meant to be discharged, e.g., to exhaustion, only once, and then discarded. Primary cells are not intended to be recharged. Primary cells are described, for example, in David Linden, Handbook of Batteries (McGraw-Hill, 2d ed. 1995). Secondary electrochemical cells can be recharged for many times, e.g., more than fifty times, more than a hundred times, or more. In some cases, secondary cells can include relatively robust separators, such as those having many layers and/or that are relatively thick. Secondary cells can also be designed to accommodate for changes, such as swelling, that can occur in the cells. Secondary cells are described, e.g., in FaIk & Salkind, "Alkaline Storage Batteries", John Wiley & Sons, Inc. 1969; U.S. Pat. No. 345,124; and French Patent No. 164,681, all hereby incorporated by reference. The details of one or more embodiments are set forth in the accompanying description below. Other aspects, features, and advantages of the invention will be apparent from the following drawings, detailed description of embodiments, and also from the appending claims. BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an illustration of an embodiment of a lithium-ion electrochemical cell. FIG. 2 is a differential scanning calorimetry (DSC) scan of a precursor in

Comparative Example 1, dried at 100 ⁰C and pelletized at 14 tons/in².

FIG. 3 is DSC scan of a precursor from an aqueous reaction OfLi₂COs, etidronic acid and ferric ammonium oxalate.

FIG. 4 is a thermogravimetric analysis (TGA) scan of a precursor from an aqueous reaction of Li₂CO₃, etidronic acid and ferric ammonium oxalate.

FIG. 5 is a scanning electron microscope (SEM) photograph of Nb-doped LiFePO₄ prepared by a solution-chelation process.

FIG. 6 is an X-ray diffraction pattern of LiFePO₄ prepared in Example 1.

DETAILED DESCRIPTION

Referring to FIG. 1, a lithium-ion electrochemical cell or battery 100 includes an anode 120 in electrical contact with a negative current collector 140, a cathode 160 in electrical contact with a positive current collector 180, a separator 200, and an electrolyte. Anode 120, cathode 160, separator 200, and the electrolyte are contained within a case 220 to maintain charge balance. Examples of batteries 100 are described in U.S. Patent No. 7,025,907, or U.S. Patent No 5,910,382, hereby incorporated by reference.

Cathode 160 includes LiFePO₄ as an electrochemically active material that is capable of receiving and releasing lithium ions. LiFePO₄ can sometimes have low intrinsic electrical conductivity and low intrinsic lithium ion diffusivity that can result in poor rate capability and power delivery. As described herein, the poor rate capability OfLiFePO₄ can be addressed by improving its electrical conductivity (such as by including carbon and/or metal doping) and improving its lithium ion diffusivity (such as by decreasing the primary crystallite size to less that 500 nm, for example, less than 100 nm, or less than 50 nm). More specifically, to reduce the crystallite size of carbon-containing (e.g., carbon coated) LiFePO₄ to less than 100 nm (e.g., less than 50 nm), a chelation-solution processing method has been developed that uses low cost precursors, is safe, has high batch yields, does not require intensive mechanical precursor milling, does not require extensive capital equipment investment, and does not require strict process or pollution control. This method combines elemental precursors at the molecular level without the need for high energy milling. The method can produce a LiFePO₄ with less than approximately 15% by weight carbon (which can enhance the intrinsic gravimetric electrochemical capacity of an electrode containing the LiFePO₄) and good electrical conductivity.

The method includes forming a water soluble precursor containing lithium, phosphorus and iron by combining a lithium source (such as lithium hydroxide), a phosphorus source (such as etidronic acid) and an iron source (such as iron oxide (e.g., Fe₂O₃) or ferric oxalate) in a solution, and then heating the precursor to form the LiFePO₄. The precursor can be prepared by first dissolving etidronic acid, or another phosphorus-containing chelation agent, in water. The lithium source (such as LiOH or Li₂CO₃) can then be added to produce a lithiated etidronic acid salt solution. The iron source (such as ferric oxalate or ferric ammonium oxalate) can then be added to produce the precursor. The added iron source can be solubilized by the lithiated etidronic acid solution to form a precursor complex containing Li, P and Fe that are mixed at the molecular level. In some embodiments, the iron source is in ferric form in order to create a soluble precursor, e.g., by using a ferric starting salt and/or oxidizing a ferrous salt in-situ. Without being bound by any particular theory, it is believed that close molecular proximity of these elements promotes LiFePO₄ formation and phase purity during calcination because the elements can travel a short distance (e.g., less than approximately 5 nm) for product formation, as compared to where the precursor elements are mechanically mixed, for example, by mechanically milling a lithium source (e.g., lithium carbonate), a phosphorus source (e.g., ammonium dihydrogen phosphate) and an iron source (e.g., ferrous oxalate) where the elements are separated by greater distances. It is also believed that the precursor is either a miscible mixture of a lithiated iron etidronic acid complex (such as Li₂Fe2CH3C(OH)[PO(O)2]2(C2θ₄)2 where etidronic acid, ferric oxalate and lithium hydroxide are the starting materials) and oxalic acid, or a single phase lithiated iron etidronic acid carboxylate complex (such as H₂Li2Fe2CH₃C(OH)[PO(O)2]2(C2θ4)3). If the precursor is a mixture, then it appears to be miscible because, upon water removal, the mixture dries to a clear transparent glass with no phase apparent separation. In embodiments in which etidronic acid, ferric ammonium oxalate and lithium hydroxide are the starting materials, it is believed that the precursor is a miscible mixture of the lithiated iron etidronic acid carboxylate complex (such as Li₂Fe2CH₃C(OH)[PO(O)2]2(C2θ4)2) and (NFLt)₂C₂O₄, or a single phase lithiated iron etidronic acid ammonium carboxylate complex (such as (NH₄)6H₂Li₂Fe₂CH3C(OH)[PO(O)₂]₂(C₂O₄)6). If the precursor is a mixture, then it appears to be miscible because, upon water removal, the mixture dries to a clear transparent glass with no apparent phase separation.

The concentration of the lithium source, phosphorus source, and iron source can each range from approximately 0.9 mol to approximately 1.1 mol. For example, the concentration of the lithium source can be greater than or equal to approximately 0.9 mol Li or approximately 1.0 mol Li; and/or less than or equal to approximately 1.1 mol Li or approximately 1.0 mol Li. The concentration of the phosphorus source can be greater than or equal to approximately 0.9 mol P or approximately 1.0 mol P; and/or less than or equal to approximately 1.1 mol P or approximately 1.0 mol P. The concentration of the iron source can be greater than or equal to approximately 0.9 mol Fe or approximately 1.0 mol Fe; and/or less than or equal to approximately 1.1 mol Fe or approximately 1.0 mol Fe.

The lithium source for preparing the precursor can contain only lithium, hydrogen, oxygen, nitrogen and carbon as elemental components to avoid contamination of the LiFePO₄ product with corrosive elements such as sulfur and halides. Examples of lithium sources include lithium carbonate, lithium acetate, lithium benzoate and/or lithium hydroxide. The moisture content of lithium carbonate, lithium benzoate and lithium acetate do not vary as much as lithium hydroxide thus their lithium assay is less sensitive to atmospheric humidity. Also, lithium hydroxide can absorb carbon dioxide if exposed to the atmosphere over time which additionally affects its lithium assay. The phosphorus source can include a phosphorus-containing chelation agent , which can be an organic phosphonate, as described, for example, in CN1803590A, U.S. 4,735,787 and U.S. 4,303,568. Examples of phosphorus-containing chelation agents include etidronic acid and iminobis(methyl-phosphonic acid). Iron sources that can produce LiFePO₄ include, but are not limited to, ferric oxalate (Fe₂(C₂O₄)S) and ammonium ferric oxalate (Fe(NHZt)₃(C₂CU)₃). The presence of ammonium moiety in the precursor, or an ammonium carboxylate in the precursor mixture, can produce a decrease of average crystallite size of the LiFePO₄-C product. Specifically, the presence of ammonium in the precursor can lower the average crystallite size of the LiFePO₄-C to less than 20 nm when calcined from 500 ⁰C to 600 ⁰C, or less than 15 nm when calcined from 500 ⁰C to 525 ⁰C. In contrast, without the presence of ammonium moiety in the precursor the average crystallite size of the LiFePO₄-C is greater than 20 nm when calcined at temperatures greater than 525 ⁰C. During calcination and LiFePO₄-C formation it is observed that precursor outgases, expands in volume by more than 5 times and loses density when ammonium ferric oxalate is used to form the precursor. Without being bound by any particular theory, it is believed that this loss of density during calcination inhibits crystallite growth by decreasing the rate of mass transport of reactants to the growing crystallite. Thus, the average LiFePO₄-C crystallite size can be affected by the method of synthesis. As indicated above, decreasing the average LiFePO₄-C crystallite size can increase the power capability OfLiFePO₄-C cathodes by decreasing the average lithium ion diffusion length through the crystallite. Proposed reactions for precursor formation and calcination are shown below:

a. Fe₂(C₂O₄)_S + 2LiOH + CH₃C(OH)[PO(OH)₂]₂ ->

Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(C₂O₄)₂ + H₂C₂O₄ + 2H₂O (precursor formation) or

H₂Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(C₂O₄)3 + 2H₂O

b. Li₂Fe₂CH₃C(OH)[PO(O)₂]₂ (C₂O₄)₂ + H₂C₂O₄ (500-700C) ->

2LiFePO₄-C + 8CO + 3H₂O (calcination) a. 2Fe(NH₄)3(C₂O₄)3 + 2LiOH + CH₃C(OH)[PO(OH)₂]₂ -> Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(C₂θ4)₂ + 3(NH₄)₂C₂O₄ + H₂C₂O₄ + 2H₂O or (NH₄)₆H₂Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(C₂O₄)6 + 2H₂O

b. Li₂Fe₂CH₃C(OH)[PO(O)₂]₂ (C₂O₄)₂ + 3(NH₄)₂C₂O₄ + H₂C₂O₄ (500-700C) -» 2LiFePO₄-C + 1 ICO + 3CO2 + 6H₂O + 6NH₃ (calcination)

Where LiFePO₄-C has a carbon content of less than approximately 15% by weight. As used herein, LiFePO₄-C and LiFePO₄ refer to the same material, which contains carbon (e.g., less than approximately 15% by weight carbon).

When molecules containing carboxylic acid anions are heated, they go through a decomposition phase that occurs around 200 ⁰C, as seen in the DSC scan in FIG. 3, whereupon they pyrolize and lose some quantity of water, CO or CO₂, or some combination of all three. The CO produced during calcination serves to reduce the Fe³⁺ iron in the precursor to Fe²⁺ iron in the LiFePO₄-C product. Carbon that is lost through pyrolization is not available for the carbothermal reduction of ferric ion that occurs at temperatures greater than 200 ⁰C. Only the carbon that remains in the solid phase of the precursor greater than 200 ⁰C (e.g., at approximately 450 ⁰C or approximately 525 ⁰C) is available for both carbothermal reduction of the ferric to the ferrous iron as well as for the formation of the electrically conductive carbon remaining in the final LiFePO₄ product. Different amounts of this residual carbon existing in the carboxylic anion above 200 ⁰C (e.g., at approximately 450 ⁰C or approximately 525 ⁰C) are dependent upon the chemical structure as well as by the number of carbon atoms in the carboxylate anion.

As an iron source, ferric oxalate can be made in-situ by an aqueous oxidation of less costly ferrous oxalate using an oxidizing agent, such as hydrogen peroxide or ozone. In the presence of a Li source, such as lithium hydroxide or lithium carbonate, and a phosphorus-containing chelation agent, such as etidronic acid, a LiFePO₄ precursor can be produced as shown below: 2FeC₂O₄ + 2LiOH + H₂O₂ + CH₃C(OH)[PO(OH)₂]₂ -> Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(C₂θ4)₂ + 4H₂O

In addition to oxalate or ammonium oxalate, other carboxylate anions can be used to produce a precursor, which the amount of carbon in the precursor, and thus the amount of carbon in LiFePO₄ to be adjusted. For example, a ferrous salt, such as ferrous oxalate, can be oxidized in an aqueous solution with an oxidizing agent, such as hydrogen peroxide or ozone, in the presence of a carboxylic acid (other than citric acid), a lithium source such as lithium carbonate or lithium hydroxide and phosphorus containing chelation agent. As a result, a mixed carboxylate precursor can form or a complete substitution of one carboxylate for another can be achieved, which can be described by the general equation (in all subsequent examples, the precursor is assumed to be a miscible mixture of a lithiated iron etidronic acid complex and a carboxylic acid and not a single phase lithiated iron etidronic acid carboxylate) :

2FeA^x _m + 2LiOH + H₂O₂ + nHB^y + CH₃C(OH)[PO(OH)₂]₂ -> Li₂Fe₂CH₃C(OH)[PO(O)₂][A]_q[B]₄₍i/_y._q/χ) + (2m-q)HA + n-(4(l/y-q/x))HB + 4H₂O

Where M= moles carboxylate per mole iron

N=moles carboxylate B

Q=moles carboxylate A incorporated into precursor

X= ionic charge of carboxylate A Y= ionic charge of carboxylate B

HA= carboxylic acid A

HB= carboxylic acid B

The total anionic charge of [A]_q[B]_4/y__4q/x =4

Since m=x/2, for ferrous salts, the equation can be simplified: 2FeA⁵V₂ + 2LiOH + H₂O₂ + nHB^y + CH₃C(OH)[PO(OH)₂]₂ -> Li₂Fe₂CH₃C(OH)[PO(O)₂][A]_q[B]4(i/_y._q/χ) + (x-q)HA + n-(4(l/y-q/x))HB + 4H₂O

One, two or more carboxylic acids can be used to produce a precursor containing one, two or more carboxylate anions. An example is illustrated below in which the carboxylic acid is propionic acid and the iron source is ferrous oxalate. As shown, a mixed carboxylate precursor containing both oxalate and propionate anion can be produced:

2FeC₂O₄ + 2LiOH + H₂O₂ + 2CH₃CH₂COOH + CH₃C(OH)[PO(OH)₂]₂ -> Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(CH₃CH₂COO)₂(C₂O₄) + H₂C₂O₄ + 4H₂O

In another example, complete substitution of oxalate for propionate can occur:

2FeC₂O₄ + 2LiOH + H₂O₂ + 4CH₃CH₂COOH + CH₃C(OH)[PO(OH)₂]₂ -> Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(CH₃CH₂COO)₄ + 2H₂C₂O₄ + 4H₂O

Carboxylic acids that produce a water soluble and homogenous precursor can be used. Examples of carboxylic acids include but are not limited to aliphatic, aromatic and/or cyclical aliphatic acids. Additionally, the carboxylic acid group can be part of a molecule that contains other functional groups such as amines, amides, epoxides, furans, ketones, ethers, aldehydes, sugars, esters and/or unsaturated groups. In addition to propionic acid, other carboxylic acids such as butyric acid, glutaric acid, benzenetetracarboxylic acid, adipic acid, tartaric acid, pyruvic acid, and sarcosine can be used to produce a water soluble and homogenous precursor as well as LiFePO₄.

In addition to carboxylic acids, ammonium carboxylates can be used. Examples of ammonium carboxylates include ammonium propionate, ammonium oxalate, ammonium adipate, ammonium benzenetetracarboxylate, ammonium butyrate, ammonium glutarate and/or ammonium sarcosate. An example is illustrated below in which the ammonium carboxylate acid is ammonium propionate and the iron source is ferrous oxalate. As shown, a mixed carboxylate precursor containing both oxalate and propionate anion can be produced:

2FeC₂O₄ + 2LiOH + H₂O₂ + 2CH₃CH₂COONH₄ + CH₃C(OH)[PO(OH)₂]₂ -> Li₂Fe₂CH3C(OH)[PO(O)₂]₂(CH3CH₂COO)₂(C₂O4) + (NH₄)₂C₂O₄ + 4H₂O

In another example, a substitution of oxalate for propionate occurs:

2FeC₂O₄ + 2LiOH + H₂O₂ + 4CH₃CH₂COONH₄ + CH₃C(OH)[PO(OH)₂]₂ -> Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(CH₃CH₂COO)₄ + 2(NH₄)₂C₂O₄ + 4H₂O

In some embodiments, the carboxylic acids are at least partially oxidized by hydrogen peroxide as judged by a darkening of the aqueous solution. These partially oxidized acids can be used to produce a precursor, for example, as long as the oxidized carboxylic acid produces a water soluble and homogenous precursor.

Examples of acids that are at least partially oxidized by hydrogen peroxide but that can be used to produce a precursor include benzenetetracarboxylic acid, 2-furoic acid and oxalic acid. Oxalic acid oxidizes to gaseous products, and therefore, excess oxalic acid may be used to maintain stoichiometry. Also, the oxalate moiety in ferrous oxalate may be oxidized by hydrogen peroxide, and as a result, can be replaced with excess oxalic acid or an oxalic acid salt such as ammonium oxalate.

In some embodiments, a precursor is prepared using a hydrated iron oxide as the iron source. An oxalic acid-buffered ammonium oxalate aqueous solution can solubilize hydrated iron oxide. The less crystalline hydrous ferric oxides are solubilized faster than the more crystalline oxides. For example, freshly prepared, poorly crystalline FeO(OH) may be converted into a precursor using ammonium oxalate as a complexing solublizer, as illustrated in the following reaction:

2FeO(OH) + 2LiOH +3(NH₄)₂ C₂O₄ + CH₃C(OH)[PO(OH)₂]₂ -> Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(C₂O₄)₂ + 3(NH₄)₂C₂O₄ + 4H₂O Ferric oxyhydroxide or ferrihydrite, FCsHOg ^H₂O, is expected to be particularly soluble in an oxalic acid-buffered ammonium oxalate aqueous solution. Less crystalline two-line ferrihydrite is expected to more readily solubilize than the more crystalline six-line ferrihydrite. Two-line and six-line refer to the number of X- ray diffraction peaks observed transposed over the amorphous diffraction pattern in the ferrihydrites. Two-line ferrihydrite can be freshly prepared by precipitation from ferric nitrate at pH 7-8 using potassium hydroxide additions followed by washing.

As indicated above, a carbon source or a carbon monoxide source is used for carbothermal reduction of iron from ferric to ferrous during LiFePO₄ formation. In some embodiments, it is believed that the carbon source needs to be present above 300 ⁰C (e.g., above 450 ⁰C) for carbothermal reduction. The carbon source can also provide enhanced electrical conductivity to the LiFePO₄ if it is carbonized during calcination. The carbon source can be from the carbon contained within the precursor molecule as well as added carbon that is not part of the precursor but is intimately mixed with the precursor by dissolving both the precursor and a carbon additive in water followed by drying. This mixing can occur during precursor formation. Examples of carbon additives include glucose, oxalic acid, 2-furoic acid, adipic acid, benzenetetracarboxylic acid, propionic acid, glutaric acid and/or ascorbic acid. Besides carbothermal reduction of iron, additional carbon is used to form an electrically conductive LiFePO₄ product. It is believed that carbon can also help prevent crystallite size from increasing.

After the iron, lithium and phosphorus sources are dissolved in water, the aqueous precursor solution is dried at an elevated temperature to form a solid precursor in which the lithium, iron and phosphorus are mixed at the molecular level. The drying temperature can be from approximately 80 to 150 ⁰C (e.g., approximately 100-130 ⁰C). The upper drying temperature can be limited by the decomposition of the organic precursor in air which can begin to occur approximately 150 ⁰C. This decomposition can accelerate above 150 ⁰C, as judged by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) (FIG. 3 and FIG. 4). The drying time can be from approximately 5 to 10 hrs (e.g., approximately 5 hrs at 130 ⁰C). When a ferrous iron source is used, such as ferrous oxalate, it is oxidized in solution using an oxidizing agent (such as hydrogen peroxide), which can be an exothermic reaction that can increase the solution temperature and the hydrogen peroxide self-decomposition rate, leaving less available to oxidize the iron. Thus, the solution can be kept cooler than 80 ⁰C (e.g., cooler than 60 ⁰C) during oxidation. Excess hydrogen peroxide can be added to account for both self-decomposition as well as hydrogen peroxide consumed due to oxidation of the carboxylic acid. Carboxylic acid can also be oxidized and possibly consumed, so therefore excess carboxylic acid, or some other organic anion, can be added to maintain precursor stoichiometry

The dried precursor can milled to a powder and pelletized, e.g., at 6-18 tons/in². The milling is not meant to mix the iron, phosphorus and lithium since they are already mixed at the molecular level. The milling serves to prepare the powder for pelletization. Pelletization is not necessary to produce phase pure LiFePO₄, however, it can prevent the powder from being blown around within the calcination furnace during vacuum and gas purging.

The precursor is ramped heated from room temperature up to a precursor decomposition temperature and then further up to a LiFePO₄ formation and crystallization temperature, under an inert atmosphere to prevent iron oxidation. During calcination, the precursor goes though three thermal stages: decomposition, LiFePO₄ formation and LiFePO₄ crystallization. DSC data indicate that decomposition occurs between 150 and 250 ⁰C. LiFePO₄ formation and crystallization occur above 450 ⁰C (e.g., approximately 525 ⁰C) and accelerate with increasing temperature. The precursor can be heated from room temperature up to approximately 200-300 ⁰C at a thermal ramp rate of 1-10 °C/min and held at 200-300 ⁰C for up to 2-5 hrs to decompose the precursor. After decomposition, the precursor can be heated from 200-300 ⁰C to more than 450 ⁰C (the LiFePO₄ formation and crystallization temperature) at a ramp rate of 0.1 to 10 °C/min and held at more than 450 ⁰C for up to 48 hours. In some embodiments, the crystallization temperature and/or time are reduced (e.g., minimized) because they can cause crystallite growth, which can reduce lithium diffusivity and subsequent rate capability. On the other hand, if insufficient crystallization occurs, this can also diminish lithium diffusivity. Thus, the minimum temperature and time at that temperature can be used for sufficient crystallization to occur for acceptable lithium diffusivity and subsequent rate capability. Crystallite growth can be inhibited by the presence of carbon coating and this can also be used to reduce (e.g., minimize) it. An additional calcination temperature consideration is formation of an electrically conductive phase including carbon (from carbonation of the organic precursor components) and/or an iron phosphide phase such as FeP, Fe₂P and/or Fe₃P (from carbothermal reduction of c- LiFePO₄ and/or presence of metallic dopants). Carbonation of the organic component OfLiFePO₄ and formation of iron phosphide phases are strongly affected by calcination temperature and to a lesser degree by calcination time. An acceptable electrical conductivity can be produced at a calcination temperature above 525 ⁰C (e.g., above approximately 600 ⁰C or above approximately 650 ⁰C). In some embodiments, the precursor pellet undergoes expansion and can foam up during calcination due the release of volatile gases. The LiFePO₄ produced in such a case has comparable physical properties to LiFePO₄ produced by precursor pellets that do not expand during calcination (e.g., they have high crystallographic phase purity and have crystallite size below 100 nm.) FIG. 5 shows well crystallized LiFePO₄ with aggregate (collection of bonded crystallites) size of approximately 2 microns or less. The formed LiFePO₄ can have low crystallite size, low carbon content, and/or good electrical conductivity. In some embodiments, the crystallite size ranges from approximately 10 nm to approximately 500 nm. The crystallite size can be greater than or equal to approximately 10 nm, approximately 50 nm, approximately 75 nm, approximately 100 nm, approximately 200 nm, approximately 300 nm, or approximately 400 nm; and/or less than or equal to approximately 500 nm, approximately 400 nm, approximately 300 nm, approximately 200 nm, approximately 100 nm, approximately 75 nm, or approximately 50 nm. In some embodiments, the carbon content ranges from approximately 0% to approximately 15%. The carbon content can be greater than or equal to approximately 0%, approximately 3%, approximately 5%, approximately 7%, approximately 9%, approximately 11%, or approximately 13%; and/or less than or equal to approximately 15%, approximately 14%, approximately 12%, approximately 10%, approximately 8%, approximately 6%, approximately 4%, or approximately 2%. In some embodiments, the electrical conductivity ranges from approximately 5X10^"11 S/cm (IHz) to approximately IXlO^"3 S/cm (IHz). The electrical conductivity can be greater than or equal to approximately 5X10^"11 S/cm (IHz), approximately IXlO^"9 S/cm (IHz), approximately IXlO^"8 S/cm (IHz), or approximately IXlO^"5 S/cm (IHz); and/or less than or equal to approximately IXlO^"3 S/cm (IHz), approximately IXlO^"5 S/cm (IHz), approximately IXlO^"8 S/cm (IHz), approximately IXlO^"9 S/cm (IHz), or approximately 5X10^"11 S/cm (IHz). One or more metallic dopants, such as Nb, Zr and Ti, can be included in cathode 160 to enhance the electrical conductivity and the rate capability OfLiFePO₄. The processes described herein can include incorporation of metallic dopant(s) and dispersal of the dopant(s) at the molecular level without the need for intensive mechanical mixing or grinding since the materials are mutually soluble. The metallic dopant(s) can be dissolved along with the lithium, iron and the phosphorus-containing chelation agent in water. Examples of aqueous soluble metallic dopants include, ammonium zirconium carbonate, ammonium vanadate, titanium(IV)bis (ammonium lactato)dihydroxide and ammonium niobate(V)oxalate hydrate. The concentration of the metallic dopant(s) can range from approximately 0.0005 mol M per mole Li to approximately 0.05 mol M per mole Li where M is a metal such as Nb, Zr and Ti. For example, the concentration of the metallic dopant(s) can be greater than or equal to approximately 0.0005 mole M per mole Li , approximately 0.005 mole M per mole Li, or approximately 0.01 mole M per mole Li; and/or less than or equal to approximately 0.05 mole M per mole Li , approximately 0.02 mole M per mole Li, or approximately 0.01 mole per mole Li.

Cathode 160 can further include a binder to enhance the structural integrity of the cathode. Examples of binders include polymers and co-polymer, such as polyethylene, polyacrylamides, styrenic block co-polymers (e.g., Kraton™ G), Viton®, and various fluorocarbon resins, including polyvinylidene fluoride (PVDF), polyvinylidene fluoride co-hexafluoropropylene (PVDF-HFP), and polytetrafluoroethylene (PTFE). Referring again to FIG. 1, anode 120 can include any material capable of reversibly receiving lithium ions during the charging process and reversibly releasing (e.g., by insertion/de -insertion or intercalation/deintercalation) these ions during the discharging process of a lithium ion battery. Examples of materials that can be included in anode 120 are graphites, carbons, Li₄TIsOi₂, tin alloys, silica alloys, intermetallic compounds, lithium metal, lithium alloys, and mixtures of any two or more thereof.

Separator 200 can include any material capable of providing electrical isolation between cathode 160 and anode 120, while allowing ions to pass through the separator. Examples of materials that can be included in separator 200 include microporous single layer of polyethylene (PE), microporous single layer of polypropylene (PP), microporous PP/PE/PP tri-layer separator, and polyolefm/inorganic hybrid microporous separator.

The electrolyte may be a solid or liquid non-aqueous electrolyte. Examples of solid electrolytes include polymeric electrolytes such as lithium salt complexes of polyethylene oxide, or dimensionally stable lithium salt solutions of gelled polymers such as polyphosphazene, and combinations thereof. Examples of liquid electrolyte solvents include ethylene carbonate, diethylene carbonate, propylene carbonate, and combinations thereof. The electrolyte can be provided with a lithium electrolyte salt. Examples of salts include LiPF₆, LiBF₄, and LiClO₄.

In the examples provided below, DC electrical conductivity was determined by mixing approximately 100 mg of sample with 5 mg of Dupont Teflon™ 6C powder in a mortar until a sheet was created. The sheet was ground into a powder using a small Waring™- type blender. The powder was then reformed into a sheet using a mortar. The sheet was reground into a powder using a small Waring™- type blender. The powder was pressed into a 1.5 cm diameter by about 0.2-0.3 mm thick pellet using a 1.5 cm die set and a pressure of 9 tons. The pellet was mounted between two 1.5 cm diameter gold-plated steel disks and 2,000 Ib of feree was applied to the disks. The DC electrical resistance was measured at IHz using a EG&G Princeton Applied Research Model 273 A potentiostat/galvanostat controlled by Zplot™ software. Carbon content was measured by a combustion technique at Galbraith Laboratories using ASTM-D5393.

Powder X-ray diffraction patterns were collected in continuous scans between 5 and 120 degrees in 2-theta using an automated Shimadzu XRD-6000 diffractometer. The X-ray diffraction patterns were structurally analyzed using the Rietveld technique with Jade™ software, available from Materials Data Inc. Crystallite size was determined using the Scherrer equation.

The following examples are illustrative and not intended to be limiting.

Examples

Example 1 - Ferric ammonium oxalate iron source and etidronic acid phosphorus source

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate was dissolved into the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat was placed in a 1.5-in diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5°C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 99.6% LiFePO₄ and 0.6% FeP, as identified by X-ray diffraction, with lattice axis parameters a=10.31805, b=6.00316, c=4.68981, and V=290.4910759 (all in angstroms, Fig 6). The Scherrer derived crystallite size is 53 nm and the carbon content is 9% (by combustion). The DC electrical conductivity is 8.5 X 10^"5 S/cm (lHz). Example 2 - Ferric oxalate iron source and iminobisfmethyl-phosphonic acid) phosphorus source

4.54 grams of iminobis(methyl-phosphonic acid) was dissolved in 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 10.8 grams of ferric oxalate was dissolved into the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat was placed in a 1.5-in diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min and held at 700 ⁰C for 10 hrs.

The final product is 99.6% LiFePO₄ and 0.6% FeP, identified by X-ray diffraction, with lattice axis parameters a=10.31427, b=6.0046, c=4.69152 and V=290.5602161 (all in angstroms). The Scherrer derived crystallite size is 58 nm and the carbon content is 5.5% (by combustion). The DC electrical conductivity is 5 X 10^"6 S/cm (lHz).

Example 3 - Ferric ammonium oxalate iron source and iminobisfmethyl-phosphonic acid) phosphorus source

4.54 grams of iminobis(methyl-phosphonic acid) was dissolved in 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate was dissolved into the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-in diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min , held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 99.9% LiFePO₄ and 0.1% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31464, b=6.00245, c=4.69067

V=290.4139718 (all in angstroms). The Scherrer derived crystallite size is 26 nm and the carbon content is 7.9% (by combustion). The DC electrical conductivity is 3 X 10^"6 S/cm (lHz).

Example 4 - Ferrous oxalate iron source and etidronic acid phosphorus source, 0.5 mole oxalic acid/mole Fe carbon additive

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 2.8 grams of oxalic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.95 grams of ferrous oxalate was added. Stirring was maintained at all times. Finally, 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, held at 700 ⁰C for 10 hrs.

The final product is 98% LiFePO₄ and 2.0% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31094 b=6.00353 c=4.69388 V=290.5607363 (all in angstroms). The Scherrer derived crystallite size is 27 nm and the carbon content is 6.9% (by combustion). The DC electrical conductivity is 1.9 X 10^"6 S/cm (lHz).

Example 5 - Ferrous oxalate iron source and etidronic acid phosphorus source, l.Omole oxalic acid/mole Fe carbon additive

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 2.8 grams of oxalic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.95 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 98% LiFePO₄, and 2.0% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31094 b=6.00353 c=4.69388 V=290.5607363 (all in angstroms). The Scherrer derived crystallite size is 27 nm and the carbon content is 6.9% (by combustion). The DC electrical conductivity is 1.9 X 10^"6 S/cm (lHz). Example 6 - Ferrous oxalate iron source and iminobisfmethyl-phosphonic acid) phosphorus source 0.5 mole oxalic acid/mole Fe carbon additive

4.54 grams of iminobis(methyl-phosphonic acid) was dissolved in 50 ml of water. 2.8 grams of oxalic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs. The final product is 98% LiFePO₄ and 2.0% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31094 b=6.00353 c=4.69388 V=290.5607363 (all in angstroms). The Scherrer derived crystallite size is 38 nm and the carbon content is 5% (by combustion). The DC electrical conductivity is 4 X 10^"8 S/cm (IHz).

Example 7 - Mixed carboxylate precursor using 1.0 mole propionic acid /mole Fe 7.72 grams of Etidronic acid solution (59% etidronic acid) and was diluted with 50 ml of water. 3.29 grams of propionic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added.

Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 98.6% LiFePO₄ and 1.4% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31837 b=6.00575 c=4.69527 V=290.963772 (all in angstroms). The Scherrer derived crystallite size is 29 nm and the carbon content is 8% (by combustion). The DC electrical conductivity is 5.4 X 10^"6 S/cm (lHz).

Example 8 - Mixed carboxylate precursor using 1.0 mole butyric acid /mole Fe

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 3.91 grams of propionic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 98.3% LiFePO₄ and 1.7% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31812 b=6.00569 c=4.69543

V=290.9637303 (all in angstroms). The Scherrer derived crystallite size is 33 nm and the carbon content is 7.8% (by combustion). The DC electrical conductivity is 7 X 10^"9 S/cm (lHz).

Example 9 - Mixed carboxylate precursor using 1.0 mole glutaric acid /mole Fe

7.72 grams of Etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 5.86 grams of glutaric acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. Finally, 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 97.9% LiFePO₄ and 2.1% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31768 b=6.00682 c=4.69718 V=291.1145253 (all in angstroms). The Scherrer derived crystallite size is 28 nm and the carbon content is 13% (by combustion). The DC electrical conductivity is 6 X 10^{" 5} S/cm (IHz). Example 10 - Mixed carboxylate precursor using 1.0 mole benzenetetracarboxylic acid /mole Fe

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 2.83 grams of benzenetetracarboxylic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. The solution may darken due to partial oxidation of the benzenetetracarboxylic acid. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 99.4% LiFePO₄ and 0.6% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31597 b=6.00414 c=4.69441 V=290.7648458 (all in angstroms). The Scherrer derived crystallite size is 34 nm and the carbon content is 8.9% (by combustion). The DC electrical conductivity is 1.9 X 10^"5 S/cm (lHz).

Example 11 - Mixed carboxylate precursor using 1.0 mole 2-furoic acid /mole Fe

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 5.00 grams of 2-furoic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. Finally, 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 100% LiFePO₄ identified by X-ray diffraction, with lattice axis parameters a=10.31754 b=6.0059 c=4.69492 V=290.9259455 (all in angstroms). The Scherrer derived crystallite size is 46 nm and the carbon content is 17.4% (by combustion). The DC electrical conductivity is 4.2 X 10^"5 S/cm (IHz).

Example 12 - Mixed carboxylate precursor using l.Omole adipic acid /mole Fe 7.72 grams of etidronic acid solution (59% etidronic acid) and was diluted with 50 ml of water. 6.5 grams of adipic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 97.1% LiFePO₄ and 2.9% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.32025 b=6.00314 c=4.68883

V=290.4913311 (all in angstroms). The Scherrer derived crystallite size is 48 nm and the carbon content is 14.6% (by combustion). The DC electrical conductivity is 5.2 X 10^"4 S/cm (lHz).

Example 13 - Mixed carboxylate precursor using 1.0 mole tartaric acid /mole Fe

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 6.67 grams of tartaric acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 100% LiFePO₄, as identified by X-ray diffraction, with lattice axis parameters a=10.32134 b=6.0031 c=4.69028 V=290.6099184 (all in angstroms). The Scherrer derived crystallite size is 86 nm and the carbon content is 1.6% (by combustion). The DC electrical conductivity was 3.6 X 10^"9 S/cm (IHz). Example 14 - Mixed carboxylate precursor using 1.0 mole pyruvic acid /mole Fe

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 3.8 grams of pyruvic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in2 in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 100% LiFePO₄, as identified by X-ray diffraction, with lattice axis parameters a=10.31751 b=6.00179 c=4.69004 V=290.4238249 (all in angstroms). The Scherrer derived crystallite size is 78 nm and the carbon content is 1.5% (by combustion). The DC electrical conductivity is 1.1 X 10^"7 S/cm (IHz).

Example 15 - Mixed carboxylate precursor using 1.0 mole sarcosine /mole Fe

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 4.0 grams of sarcosine was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 100% LiFePO₄, as identified by X-ray diffraction, with lattice axis parameters a=10.31727 b=6.00183 c=4.69087 V=290.4704004 (all in angstroms). The Scherrer derived crystallite size is 47 nm and the carbon content is 4.2% (by combustion). The DC electrical conductivity is 1 X 10^"7 S/cm (IHz).

Example 16 - Mixed carboxylate precursor using 0.4 mole 2-furoic acid /mole Fe and 0.5mole ammonium oxalate/mole Fe

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 2.00 grams of 2-furoic acid and 3.15 grams ammonium oxalate was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 14 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs. The final product is 98.8% LiFePO₄ and 1.2%Fe₂P identified by X-ray diffraction, with lattice axis parameters a=10.32236 b=6.00587 c=4.69442 V=291.0294049 (all in angstroms). The Scherrer derived crystallite size is 47nm and the carbon content is 6% (by combustion). The DC electrical conductivity is 2 XlO^"5 S/cm (IHz).

Example 17 - Mixed carboxylate precursor using 1.0 mole benzenetetracarboxylic acid /mole Fe calcined at 525 ⁰C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 2.83 grams of benzenetetracarboxylic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. The solution may darken due to partial oxidation of the benzenetetracarboxylic acid. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 525°C at 2 °C/min, and held at 525°C for 15 hrs. The final product is 100% LiFePO₄, as identified by X-ray diffraction, with lattice axis parameters a=10.32103 b=6.00317 c=4.70039 V=291.230983 (all in angstroms). The Scherrer derived crystallite size is 32 nm and the carbon content is 8% (by combustion). The DC electrical conductivity is 1.8 X 10^"10 S/cm (IHz). Example 18 - Mixed carboxylate precursor using 1.0 mole adipic acid /mole Fe calcined at 525°C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 6.5 grams of adipic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 525 ⁰C at 2 °C/min, and held at 525 ⁰C for 15 hrs.

The final product is 98.2% LiFePO₄ and 1.8% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31661 b=6.00457 c=4.70176 V=

291.2590188 (all in angstroms). The Scherrer derived crystallite size is 18 nm and the carbon content is 14.5% % (by combustion). The DC electrical conductivity is 3.8 X 10^"10 S/cm (lHz).

Example 19 - Ferrous oxalate iron source and etidronic acid phosphorus source (no excess carbon source)

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.95 grams of ferrous oxalate was added. Stirring was maintained at all times. 14 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 100% LiFePO₄, as identified by X-ray diffraction, with lattice axis parameters a=10.32134 b=6.0031 c=4.69028 V=290.6099184 (all in angstroms). The Scherrer derived crystallite size is 206 nm and the carbon content is <0.5% (by combustion). The DC electrical conductivity is 3.4 X 10^"9 S/cm (IHz).

Example 20 - Ferric ammonium oxalate iron source and 1 mole % Nb doping

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate and 0.2 grams of ammonium niobate(V)oxalate hydrate was dissolved in the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs. The calcined product foamed up during calcination.

The final product is 99.8% LiFePO₄ and 0.2% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31232 b=6.00652 c=4.69008 V=290.5089785 (all in angstroms). The Scherrer derived crystallite size is 46 nm and the carbon content is 9.5% (by combustion). The DC electrical conductivity is 5.6 X 10^"6 S/cm (lHz).

Example 21 - Ferric ammonium oxalate iron source and 1 mole % Zr doping 7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate and 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved in the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs. The calcined product foamed up during calcination.

The final product is 97.1% LiFePO₄ and 2.9% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31765 b=6.00444 c=4.69066 V=290.5944097 (all in angstroms). The Scherrer derived crystallite size is 48 nm and the carbon content is 9.3% (by combustion). The DC electrical conductivity is 3.3 X 10^"5 S/cm (lHz). Example 22 - Ferric ammonium oxalate iron source and 1 mole % Ti doping

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate and 0.26 grams titanium(IV)bis (ammonium lactato)dihydroxide solution

(50% w/w aqueous) was dissolved in the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5 -inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs. The calcined product foamed up during calcination.

The final product is 97.6% LiFePO₄ and 2.4% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.31204 b=6.00431 c=4.69314 V=290.5836705 (all in angstroms). The Scherrer derived crystallite size is 47 nm and the carbon content is 9.8% (by combustion). The DC electrical conductivity is 4 X 10^"5 S/cm (lHz).

Example 23 - Ferric ammonium oxalate iron source and 1 mole % V doping 7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate and 0.14 grams ammonium vanadate was dissolved in the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5 -inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs. The calcined product foamed up during calcination.

The final product is 98.2% LiFePO₄ and 1.8% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.30896 b=6.00593 c=4.69627

V=290.7690505 (all in angstroms). The Scherrer derived crystallite size is 47 nm and the carbon content is 10% (by combustion). The DC electrical conductivity is 1.1 X 10^"5 S/cm (lHz).

Example 24 - Ferric ammonium oxalate iron source and 1 mole % Zr doping calcined at 525°C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate and 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved in the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 525°C at 2 °C/min, and held at 525°C for 15 hrs. The calcined product foamed up during calcination. The final product is 100% LiFePO₄ , identified by X-ray Diffraction, with lattice axis parameters a=10.32216 b=6.01095 c=4.70002 V=291.6173829 (all in angstroms). The Scherrer derived crystallite size is 13nm and the carbon content is 10.5% (by combustion). The DC electrical conductivity is 3.2 X 10^"9 S/cm (IHz).

Example 25 - Ferric ammonium oxalate iron source and 1 mole % Ti doping calcined at 525°C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate and 0.26 grams titanium(IV)bis (ammonium lactato)dihydroxide solution (50% w/w aqueous) was dissolved in the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5 -inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 525°C at 2 °C/min, and held at 525°C for 15 hrs. The calcined product foamed up during calcination.

The final product is 100% LiFePO₄, identified by X-ray Diffraction, with lattice axis parameters a=10.32036 b=6.00949 c=4.7004 V=291.5192791 (all in angstroms). The Scherrer derived crystallite size is 14nm and the carbon content is 10.5% (by combustion). The DC electrical conductivity is 1.6 X 10 ⁹ S/cm (IHz).

Example 26 - Ferric ammonium oxalate iron source and 1 mole % Ti doping calcined at 600 ⁰C 7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate and 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved in the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 600 ⁰C at 2 °C/min, and held at 600 ⁰C for 10 hrs. The calcined product foamed up during calcination. The final product is 100 % LiFePO₄ identified by X-ray Diffraction, with lattice axis parameters a=10.3163 b=6.00961 c=4.69796 V=291.2591426 (all in angstroms). The Scherrer derived crystallite size is 18nm and the carbon content is 9.6% (by combustion). The DC electrical conductivity is 4.5X 10^"8 S/cm (IHz).

Example 27 - Ferric ammonium oxalate iron source and 1 mole % Zr doping calcined at 600 ⁰C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate and 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved in the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 600 ⁰C at 2 °C/min, and held at 600 ⁰C for 10 hrs. The calcined product foamed up during calcination.

The final product is 100% LiFePO₄, identified by X-ray Diffraction, with lattice axis parameters a=10.31865 b=6.00886 c=4.69809 V=291.2971929 (all in angstroms). The Scherrer derived crystallite size is 16nm and the carbon content is 10.1 % (by combustion) . The DC electrical conductivity is 9 X 10 ⁸ S/cm S/cm ( 1 Hz) .

Example 28 - Ferrous oxalate iron source and etidronic acid phosphorus source, 1 mole oxalic acid/mole Fe carbon additive, 1 mole % Zr doped and calcined at 700 ⁰C 7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 5.6 grams of oxalic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.95 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After the ferrous oxalate dissolved, 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 5 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs. The final product is 100% LiFePO₄, identified by X-ray Diffraction, with lattice axis parameters a=10.32106 b=6.00397 c=4.69147 V=290.7178913 (all in angstroms). The Scherrer derived crystallite size is 34nm and the carbon content is 3.0% (by combustion). The DC electrical conductivity is 1.2 X 10^"9 S/cm (IHz).

Example 29- Ferrous oxalate iron source and etidronic acid phosphorus source, 1 mole oxalic acid/mole Fe carbon additive, 1 mole% Zr doped and calcined at 400⁰C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 5.6 grams of oxalic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.95 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After the ferrous oxalate dissolved, 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 5 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 400⁰C at 2 °C/min, add held at 400⁰C for 15 hrs. The final product is amorphous based on X-ray Diffraction. The carbon content is 4.9% (by combustion). The DC electrical conductivity is 3.8 X 10^"10 S/cm (IHz). Example 30 - Ferrous oxalate iron source and etidronic acid phosphorus source, 1 mole oxalic acid/mole Fe carbon additive, 1 mole% Zr doped and calcined at 450⁰C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 5.6 grams of oxalic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.95 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After the ferrous oxalate dissolved, 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 5 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 450⁰C at 2 °C/min, and held at 450⁰C for 15 hrs.

The final product is 100% LiFePO₄, identified by X-ray Diffraction, with lattice axis parameters a=10.32059 b=6.00411 c=4.69603 V=290.993996 (all in angstroms). The Scherrer derived crystallite size is 28nm and the carbon content is 3.8% (by combustion). The DC electrical conductivity is 2.0 X 10^"10 S/cm (IHz).

Example 31 - Ferrous oxalate iron source and etidronic acid phosphorus source, 1 mole oxalic acid/mole Fe carbon additive, 1 mole % Zr doped and calcined at 525 ⁰C 7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 5.6 grams of oxalic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.95 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After the ferrous oxalate dissolved, 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 5 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5 -inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 525 ⁰C at 2 °C/min, and held at 525 ⁰C for 15 hrs. The final product is 100% LiFePO4 , identified by X-ray diffraction, with lattice axis parameters a=10.31486 b=6.00132 c=4.69457 V=290.6069133 (all in angstroms).

The Scherrer derived crystallite size is 33nm. The DC electrical conductivity is 1.8 X 10-9 S/cm (IHz).

Example 32 - Mixed carboxylate precursor using 1.0 mole propionic acid /mole Fe, 1 mole % Zr doped and calcined at 525°C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 3.29 grams of propionic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After the ferrous oxalate dissolves, 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 5 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5 -inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 525°C at 2 °C/min, and held at 525 ⁰C for 15 hrs.

The final product is 100% LiFePO₄, identified by X-ray Diffraction, with lattice axis parameters a=10.31451 b=6.00361 c=4.7006 V=291.0813429 (all in angstroms). The Scherrer derived crystallite size is 22nm and the carbon content is 8.2% (by combustion). The DC electrical conductivity is 2.8 X 10^"9 S/cm (IHz).

Example 33 - Mixed carboxylate precursor using 1.0 mole propionic acid /mole Fe and calcined at 450 ⁰C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 3.29 grams of propionic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 5 hrs.

After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 450⁰C at 2 °C/min, and held at 450 ⁰C for 15 hrs.

The final product is 100% LiFePO₄, identified by X-ray Diffraction, with lattice axis parameters a=10.3245 b=6.00703 c=4.70298 V=291.6768502 (all in angstroms). The Scherrer derived crystallite size is 24nm and the carbon content is 8.7% (by combustion). The DC electrical conductivity is 5.0 X 10^~π S/cm (IHz).

Example 34 - Ferric ammonium oxalate iron source and 1 mole % Zr doping calcined at 450⁰C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 16.85 grams of ferric ammonium oxalate and 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved in the solution. All dissolutions were performed at room temperature. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 450⁰C at 2 °C/min, and held at 450⁰C for 15 hrs. The calcined product foamed up during calcination.

The final product is amorphous, identified by X-ray Diffraction. The carbon content is 11.6% (by combustion). The DC electrical conductivity is 6.1 X 10^"10 S/cm (IHz).

Example 35 - Mixed carboxylate precursor using 1.0 mole propionic acid /mole Fe, lmole % Zr doped and calcined at 600 ⁰C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 3.29 grams of propionic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After the ferrous oxalate dissolves, 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 5 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5 -inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 525°C at 2 °C/min, held at 525°C for 5 hrs, ramped to 600 ⁰C at 2 °C/min, and held at 600 ⁰C for 10 hrs.

The final product is 99.9% LiFePO₄ and 0.1% Fe₇C₃, identified by X-ray Diffraction, with lattice axis parameters a=10.31433 b=6.00376 c=4.69723V=

290.8748492 (all in angstroms). The Scherrer derived crystallite size is 23nm and the carbon content is 8.5% (by combustion). The DC electrical conductivity is 8.2 X 10^"9 S/cm (IHz).

Example 36 - Mixed carboxylate precursor using 1.0 mole propionic acid/mole Fe, 1 mole % Zr doped and calcined at 700 ⁰C

7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 3.29 grams of propionic acid was next added and dissolved. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 7.99 grams of ferrous oxalate was added. Stirring was maintained at all times. 7 grams of 50% H₂O₂ was slowly added. Heat was generated so the solution was kept between 30 ⁰C and 50 ⁰C with a water bath. After the ferrous oxalate dissolves, 0.255 grams of ammonium zirconium (IV) carbonate solution (15.1% Zr, stabilized with 1-2% tartaric acid) was dissolved. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 5 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5 -inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 525°C at 2 °C/min, held at 525°C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final product is 99.3% LiFePO₄ and 0.7% Fe₂P, identified by X-ray Diffraction, with lattice axis parameters a=10.31667 b=6.00588 c=6.00588

V=372.1284209 (all in angstroms). The Scherrer derived crystallite size is 27nm and the carbon content is 8.0% (by combustion). The DC electrical conductivity is 1.7 X 10^"6 S/cm (lHz).

A water-soluble single compound LiFePO₄ precursor can be prepared using an aqueous acid-base reaction of a lithium source such as lithium hydroxide, an iron source such as ferric citrate or ferric nitrate, and a phosphorus containing chelation agent such as etidronic acid CH₃C(OH)[PO(OH)₂]2 which contains 4 acid groups capable of an acid-base reaction with lithium and a chelation reaction with iron. The resulting precursor contains ferric cations that are subsequently reduced to ferrous cations by a carbothermal reaction with carbon within the precursor molecule. The final products were a carbon containing LiFePO₄ designated as LiFePO₄-C where c is the percentage of carbon. Without being limited by theory, it was believed the reactions can be illustrated as follows (stoichiometrically assuming no excess carbon):

Ferric citrate source a. 6LiOH + 6FeC₆H₅O₇ + 3CH₃C(OH)[PO(OH)₂]₂ -> Li₆Fe₆3[[CH₃C(OH)[PO(O)₂]₂]][C₆H₅O₇]₄ + 6H₂O + 2C₆H₈O₇

b. Li₆Fe₆3[[CH₃C(OH)[PO(O)₂]2]][C₆H₅O₇]₄ + 2C₆H₈O₇ (500-700 ⁰C) ->

6LiFePO₄ + 5CO₂ + 2CO + 29C + 20H₂O In step a, the solution was dried at 130 ⁰C, resulting in an intimate mixture of Li₆Fe63[[CH₃C(OH)[PO(O)₂]₂]][C6H₅θ7]4 and citric acid.

In step b, both of these compounds are calcined, and during calcination Li, P and Fe remain mixed at the molecular level. For the purposes of equation balancing, it was assumed that there was no carbon volatilization of the mixed precursor below 300 ⁰C, but there may be some carbon volatilization below 300 ⁰C as indicated by DSC and TGA. The CO produced during calcination and the carbon serve to reduce the Fe³⁺ in the precursor to Fe²⁺ in the LiFePO₄ product.

Ferric nitrate source a. 2LiOH + 2Fe(NO₃)₃ + CH₃C(OH)[PO(OH)₂]₂ ->

Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(Nθ3)4 + 2H₂O + 2HNO₃

b. Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(NO₃)₄ + 1/2C (500-700 ⁰C) ->

2LiFePO₄ + 1/2CO₂ + 2H₂O + 4NO₂

In step a, the solution was dried at 100 ⁰C resulting in Li₂Fe₂CH₃C(OH)[PO(O)₂]₂(NO₃)₄ and HNO₃ . In step b, both of these compounds are calcined, and during calcination Li, P and Fe remain mixed at the molecular level.

It was found that LiFePO₄ produced using a phosphorus-containing chelation agent and ferric citrate produces LiFePO₄ with a high carbon content of 17.5% (Comparative Example 1). This high carbon content can reduce the intrinsic gravimetric electrochemical capacity of an electrode containing this LiFePO₄ product.

It was also found that LiFePO₄ produced using a phosphorus-containing chelation agent and ferric nitrate can cause an explosive reaction, possibly between the nitrate moiety and the organic components of the precursor. This reaction was illustrated by a DSC analysis (FIG. 2) of the LiFePO₄ precursor produced by the aqueous reaction of etidronic acid, lithium carbonate and ferric nitrate, followed by drying at 100 ⁰C, then pelletized at 17 tons/in² (Comparative Example 2). The precursor exploded at 150 ⁰C.

Comparative Example 1 - Ferric citrate iron source 7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 11.75 grams of ferric citrate was dissolved in the solution at 60⁰C. After dissolution, the solution was poured into a Pyrex dish and dried at 130 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pelletized precursor was then placed in a copper foil covered ceramic boat, and the boat placed in a 1.5-inch diameter tube furnace. The tube furnace was vacuum evacuated 3 times, the last evacuation being for 15 minutes, and back filled with argon. Argon gas was then purged at a constant 80 cc/min. The furnace was heated from room temperature to 200 ⁰C at 5 °C/min, held at 200 ⁰C for 2 hrs, ramped to 500 ⁰C at 2 °C/min, held at 500 ⁰C for 5 hrs, ramped to 700 ⁰C at 2 °C/min, and held at 700 ⁰C for 10 hrs.

The final products were 95.5% LiFePO₄ and 4.5% Fe₂P, as identified by X-ray diffraction, with lattice axis parameters a=10.32475 b=6.00686 c=4.69261 V=291.0325178 (all in angstroms). The Scherrer derived crystallite size was 49 nm and the carbon content was 17.5% (by combustion). The DC electrical conductivity was l.l X 10^"3 S/cm (lHz).

Comparative Example 2 - Ferric nitrate iron source 7.72 grams of etidronic acid solution (59% etidronic acid) was diluted with 50 ml of water. 1.64 grams of lithium carbonate was slowly added with stirring. After effervescence ceased, 150 ml of water was added. 17.9 grams of ferric nitrate was dissolved in the solution at 60 ⁰C. After dissolution, the solution was poured into a Pyrex dish and dried at 100 ⁰C for 10 hrs. After drying, the precursor was scraped from the dish into a mortar and briefly ground into a powder. 4 grams of precursor powder was pelletized at 16 tons/in² in a 1-inch diameter die. The pellet was heated in a differential scanning calorimeter under argon gas flow from room temperature to 600 ⁰C. The pelletized precursor exploded at 150 ⁰C as shown in FIG. 2. Other embodiments are within the scope of the following claims.

Claims

What is claimed is:

1. A method, comprising: combining a lithium source, a phosphorus source, and an iron source into an aqueous solution; forming LiFePO₄ from the solution, the LiFePO₄ comprising less than approximately 15% by weight of carbon; and forming an electrode comprising the LiFePO₄.

2. The method of claim 1 , wherein the LiFePO₄ comprises from approximately 1% by weight to approximately 15% by weight of carbon.

3. The method of claim 1 , wherein the LiFePO₄ has an average crystallite size of less than approximately 100 nm.

4. The method of claim 1 , wherein the LiFePO₄ has a DC electrical conductivity of equal to or greater than approximately I X lO^"9 S/cm (IHz).

5. The method of claim 1 , wherein the lithium source comprises a material selected from the group consisting of lithium hydroxide, lithium carbonate, lithium benzoate, and lithium acetate.

6. The method of claim 1 , wherein the phosphorus source comprises a phosphorus-containing chelation agent.

7. The method of claim 6, wherein the chelation agent comprises a material selected from the group consisting of editronic acid and iminobis(methyl-phosphonic acid).

8. The method of claim 1 , wherein the iron source comprises a material selected from the group consisting of iron oxide and iron carboxylate.

9. The method of claim 8, wherein the iron source comprises a material selected from the group consisting of ferric oxalate, ferric ammonium oxalate, ferrous oxalate, hydrated iron oxide, iron ammonium carboxylate, and ferric oxyhydroxide.

10. The method of claim 1 , further comprises combining in the aqueous solution an oxidizing agent capable of oxidizing the iron source.

11. The method of claim 10, wherein the oxidizing agent comprises hydrogen peroxide or ozone.

12. The method of claim 1, further comprising combining in the aqueous solution a carboxylic acid.

13. The method of claim 12, wherein the carboxylic acid is selected from the group consisting of oxalic acid, 2-furoic acid, adipic acid, benzenetetracarboxylic acid, propionic acid, glutaric acid, pyruvic acid, tartaric acid and sarcosine.

14. The method of claim 1, further comprising combining in the aqueous solution a soluble metal source different from the lithium source and the iron source.

15. The method of claim 14, wherein the metal source comprises niobium, zirconium, vanadium or titanium.

16. The method of claim 15, wherein the metal source is selected from the group consisting of ammonium zirconium carbonate, ammonium vanadate, titanium(IV)bis (ammonium lactato)dihydroxide and ammonium niobate(V)oxalate hydrate.

17. The method of claim 1, further comprising combining in the aqueous solution a carbon additive.

18. The method of claim 17, wherein the carbon additive is selected from the group consisting of glucose, oxalic acid, 2-furoic acid, adipic acid, benzenetetracarboxylic acid, propionic acid, glutaric acid and ascorbic acid.

19. The method of claim 1, wherein forming the LiFePO₄ comprises removing water from the aqueous solution.

20. The method of claim 1, wherein the aqueous solution is substantially free of a nitrate ion or a citrate ion.

21. The method of claim 1 , further comprising using the electrode to make a lithium ion battery.

22. The method of claim 1, wherein forming the LiFePO₄ is substantially free of mechanical mixing.

23. A method, comprising : forming a precursor comprising lithium, iron, phosphorus and an ammonium moiety; forming LiFePO₄ from the precursor; and forming an electrode comprising the LiFePO₄.

24. The method of claim 23, wherein the LiFePO₄ formed from the precursor has an average crystallite size of less than 20 nm.

25. The method of claim 23, wherein the LiFePO₄ formed from the precursor has an average crystallite size of less than 15 nm.

26. The method of claim 23, wherein the LiFePO₄ formed from the precursor comprises from approximately 1% by weight to approximately 15% by weight of carbon.

27. The method of claim 23, wherein the LiFePO₄ has a DC electrical conductivity of equal to or greater than approximately I X lO^"9 S/cm (IHz).

28. The method of claim 23, wherein forming the precursor comprises including in an aqueous solution a lithium source selected from the group consisting of lithium hydroxide, lithium carbonate, lithium benzoate, and lithium acetate.

29. The method of claim 23, wherein forming the precursor comprises including in an aqueous solution a phosphorus source comprising a phosphorus- containing chelation agent.

30. The method of claim 29, wherein the chelation agent comprises a material selected from the group consisting of editronic acid and iminobis(methyl- phosphonic acid).

31. The method of claim 23, wherein forming the precursor comprises including in an aqueous solution an iron source selected from the group consisting of iron oxide and iron carboxylate.

32. The method of claim 31 , wherein the iron source comprises a material selected from the group consisting of ferric oxalate, ferric ammonium oxalate, ferrous oxalate, hydrated iron oxide, iron ammonium carboxylate, and ferric oxyhydroxide.

33. The method of claim 23, wherein forming the precursor comprises including in an aqueous solution an oxidizing agent capable of oxidizing iron.

34. The method of claim 33, wherein the oxidizing agent comprises hydrogen peroxide or ozone.

35. The method of claim 23, wherein forming the precursor comprises including in an aqueous solution a carboxylic acid.

36. The method of claim 35, wherein the carboxylic acid is selected from the group consisting of oxalic acid, 2-furoic acid, adipic acid, benzenetetracarboxylic acid, propionic acid, glutaric acid, pyruvic acid, tartaric acid and sarcosine.

37. The method of claim 23, wherein forming the precursor comprises including in an aqueous solution a soluble metal source different from lithium and iron.

38. The method of claim 37, wherein the metal source comprises niobium, zirconium, vanadium or titanium.

39. The method of claim 38, wherein the metal source is selected from the group consisting of ammonium zirconium carbonate, ammonium vanadate, titanium(IV)bis (ammonium lactato)dihydroxide and ammonium niobate(V)oxalate hydrate.

40. The method of claim 23, wherein forming the precursor comprises including in an aqueous solution a carbon additive.

41. The method of claim 40, wherein the carbon additive is selected from the group consisting of glucose, oxalic acid, 2-furoic acid, adipic acid, benzenetetracarboxylic acid, propionic acid, glutaric acid and ascorbic acid.

42. The method of claim 23, wherein forming the LiFePO₄ comprises removing water from an aqueous solution.

43. The method of claim 42, wherein the aqueous solution is substantially free of a nitrate ion or a citrate ion.

44. The method of claim 23, further comprising using the electrode to make a lithium ion battery.

45. The method of claim 23, wherein forming the LiFePO₄ is substantially free of mechanical mixing.