Phosphoric acid abrasives and methods of use thereof

Abstract

A grinding process includes the step of combining FePO4, Li2CO3, water, a carbon source, and an abrasive to form a slurry, the abrasive of the slurry having structure (I) wherein n of structure (I) is from 1 to 10, and R1 is selected from the group consisting of hydrogen, an alkylphenyl group, a linear or branched primary or secondary alkyl chain, and R2 is selected from the group consisting of hydrogen, a methyl group, an ethyl group, or a combination thereof; and grinding the slurry.

Description

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

[0001] The present disclosure relates to abrasives, and more particularly to methods of using phosphoric acid abrasives.

[0002] Introduction

[0003] The advent of battery-powered consumer electronics and now vehicles has greatly increased the demand for lithium-ion batteries and products used to manufacture such batteries. In each lithium-ion battery, there is typically a cathode composed of LiFePO 4 (“LFP”). The industrial manufacture of LFP is accomplished through a variety of processes, but the most popular is solid-state synthesis. The solid-state synthesis of LFP involves multiple steps. In the first step of preparing LFP, raw materials (FePO 4 , Li 2 CO 3 , a carbon source, and an abrasive) are dispersed in water and sanded until the raw material particle size of the resulting slurry reaches a D 50 of about 400 nm or less. Next, the slurry is spray-dried to obtain agglomerated particles of the mixed raw materials. The resulting spray-dried particle size should exhibit a D 50 of about 10 μm. Finally, the spray-dried LFP particles are calcined in an N 2 atmosphere. Thereby, LFP can be made into a cathode for battery manufacturing.

[0004] One of the most time-consuming processes in LFP manufacture is the grinding time of the raw components. Grinding the raw material components of LFP can take more than 8 hours to reach the desired D 50 particle size. During the grinding process, an abrasive is used to help disperse the solid raw materials to improve the grinding efficiency. High sanding efficiency means less grinding time, which will result in higher production efficiency, lower costs, and better sustainability. Therefore, using high-performance abrasives can significantly promote the development of LFP. An abrasive that achieves a particle size within 1% of 400 nm (i.e., 404 nm) or less within 4 hours of grinding will significantly improve the efficiency of the grinding process.

[0005] Considering the electrochemical properties of the battery, the choice of materials used and when that material is used to manufacture LFP and LFP-based cathodes involves more considerations. For example, most abrasives are surfactants such as sodium dodecyl sulfate (“SDS”), cetyltrimethylammonium bromide (“CTAB”), and polyethylene glycol (“PEG”). However, for SDS and CTAB, the heteroatoms present in such abrasives, such as S, N, and Br, will greatly reduce the electrochemical stability of the LFP cathode. In addition, metal ions, such as Na + , will interfere with Li +Transportation and greatly affect the electrical properties of LFP. Therefore, materials neutralized with alkali atoms, such as those provided in JP2014149968A, should be avoided because such neutralization introduces undesirable heteroatoms. Ideally, the abrasive should not introduce detectable S, N, Br, and metal ions into the LFP slurry.

[0006] In view of the above, it is surprising and advantageous to find an abrasive and method that not only achieve a particle size within 1% of 400 nm (i.e., 404 nm) or less within 4 hours of grinding, but also do not introduce S, N, Br, and metal ions into the LFP slurry. Summary of the Invention

[0007] The inventors of the present disclosure have found an abrasive and method that not only achieve a particle size within 1% of 400 nm (i.e., 404 nm) or less within 4 hours of grinding, but also do not introduce S, N, Br, and metal ions into the LFP slurry.

[0008] This disclosure is the result of discovering that the affinity between FePO 4 and the abrasive can be increased by using an abrasive containing an unneutralized phosphoric acid moiety. It has been found that the increased affinity between the abrasive including the phosphoric acid moiety and FePO 4 allows FePO to be ground faster than conventional abrasives 4 to within 1% of 400 nm. In addition, by using the unneutralized phosphoric acid moiety in the abrasive, the abrasive does not contribute heteroatoms to the LFP slurry and any resulting product. Therefore, using the abrasive of the present invention in the grinding process not only saves time and energy in grinding, but also avoids contaminating the LFP slurry as conventional abrasives do.

[0009] According to a first feature of the present disclosure, the grinding method includes the steps of: combining FePO 4 , Li 2 CO 3 , water, a carbon source, and an abrasive to form a slurry, the abrasive of the slurry having structure (I), wherein n in structure (I) is from 1 to 10, and R 1 is selected from the group consisting of hydrogen, an alkylphenyl group, a linear or branched primary alkyl chain or secondary alkyl chain, and R 2 is selected from the group consisting of hydrogen, a methyl group, an ethyl group, or a combination thereof; and grinding the slurry.

[0010] According to a second feature of the present disclosure, the step of grinding the slurry further includes grinding the slurry for 4 hours to obtain a slurry D 50 particle size of 404 nm or less as measured according to particle size testing.

[0011] According to a third feature of the present disclosure, FePO4 , Li 2 CO 3 The step of combining Li, CO, water, a carbon source, and an abrasive to form a slurry further includes combining FePO 4 , Li 2 CO 3 , water, a carbon source, an abrasive, and polyethylene glycol to form a slurry.

[0012] According to a fourth feature of the present disclosure, the carbon source is glucose.

[0013] According to a fifth feature of the present disclosure, R in structure (I) 2 is hydrogen.

[0014] According to a sixth feature of the present disclosure, R 1 is not hydrogen and the total number of carbon atoms in structure (I) is from 6 to 18.

[0015] According to a seventh feature of the present disclosure, R 1 is an alkylphenol selected from the group consisting of octylphenyl, nonylphenyl, and combinations thereof.

[0016] According to an eighth feature of the present disclosure, R 1 is C 12 -C 14 secondary alkyl.

[0017] According to a ninth feature of the present disclosure, the slurry contains 20 wt% to 30 wt% of FePO based on the total weight of the slurry; 1 wt% to 10 wt% of Li, CO based on the total weight of the slurry; 5 wt% to 15 wt% of a carbon source based on the total weight of the slurry; 50 wt% to 70 wt% of water based on the total weight of the slurry; and 0.1 wt% to 5 wt% of an abrasive based on the total weight of the slurry. 4 ; 1 wt% to 10 wt% of Li, CO based on the total weight of the slurry; 2 CO 3 ; 5 wt% to 15 wt% of a carbon source based on the total weight of the slurry; 50 wt% to 70 wt% of water based on the total weight of the slurry; and 0.1 wt% to 5 wt% of an abrasive based on the total weight of the slurry.

[0018] According to a tenth feature of the present disclosure, the slurry contains 1 wt% to 2 wt% of an abrasive based on the total weight of the slurry. Detailed Description

[0019] As used herein, the term "and / or" when used in a list of two or more items means that any one of the listed items can be used alone or any combination of two or more of the listed items can be used. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0020] Unless otherwise specified, all ranges include endpoints.

[0021] The test method refers to the latest test method as of the priority date of this document, unless the date is expressed as a two-digit number with a hyphen using the test method number. A reference to a test method includes a reference to both the test society and the test method number. The test method organization is referred to by one of the following abbreviations: ASTM refers to ASTM International (formerly known as the American Society for Testing and Materials); IEC refers to the International Electrotechnical Commission; EN refers to European Standards; DIN refers to the German Institute for Standardization; and ISO refers to the International Organization for Standardization.

[0022] As used herein, unless otherwise specified, the term weight percent (“wt%”) means the weight percentage of a component based on the total weight of the polymer composition.

[0023] As used herein, the Chemical Abstracts Service Registry Number (“CAS#”) refers to the unique numerical identifier that has been most recently assigned by the Chemical Abstracts Service to a chemical compound as of the priority date of this document.

[0024] Method

[0025] This disclosure relates to a grinding method. The method includes the following steps: combining FePO 4 , Li 2 CO 3 , water, a carbon source, and an abrasive to form a slurry and grinding the slurry. The grinding of the slurry can be carried out in a bead mill, a sand mill, a basket mill, or other types of mills configured to use grinding media to grind the particles in the slurry into small and uniform sizes. The grinding media (i.e., beads, sand, etc.) are typically spherical and have a diameter in the range of 0.1 mm to 5 mm. The grinding media are harder than the components of the slurry being ground. During grinding, the slurry and the grinding media can be rotated, tumbled, shaken, or otherwise agitated to effect the grinding of the slurry. In an example where grinding is accomplished by rotation, the mill can be rotated at a speed of 500 revolutions per minute (“rpm”) to 2000 rpm. The grinding of the slurry can be carried out for 1 hour or longer, or 2 hours or longer, or 3 hours or longer, or 4 hours or longer, or 5 hours or longer, or 6 hours or longer, or 7 hours or longer, or 8 hours or longer, or 9 hours or longer, and at the same time, for a period of 10 hours or shorter, or 9 hours or shorter, or 8 hours or shorter, or 7 hours or shorter, or 6 hours or shorter, or 5 hours or shorter, or 4 hours or shorter, or 3 hours or shorter, or 2 hours or shorter.

[0026] Carry out the grinding of the slurry for a period of time until the particles of FePO 4 and Li 2 CO 3 reach the desired D 50 particle size. D50 The particle size is the median particle size of the distribution and represents that 50% by volume of the particles are larger than the D 50 value and 50% of the particles are smaller than the D 50 value. The D 50 particle size is determined by a particle size test explained in more detail below. The slurry may have a D 50 particle size of 404 nm or less, or 400 nm or less, or 380 nm or less, or 360 nm or less, or 340 nm or less, or 320 nm or less, or 300 nm or less, or 280 nm or less, or 260 nm or less, or 240 nm or less, or 220 nm or less, or 200 nm or less as measured by the particle size test.

[0027] Iron Phosphate

[0028] The slurry contains iron phosphate. The iron phosphate has the chemical formula of FePO 4 . The iron phosphate can be added to the slurry as a powder, multiple particles or as an aqueous dispersion. The slurry contains 20 wt% to 30 wt% of FePO 4 based on the total weight of the slurry. For example, the slurry may contain 20 wt% or more, or 21 wt% or more, or 22 wt% or more, or 23 wt% or more, or 24 wt% or more, or 25 wt% or more, or 26 wt% or more, or 27 wt% or more, or 28 wt% or more, or 29 wt% or more of iron phosphate, and at the same time, 30 wt% or less, or 29 wt% or less, or 28 wt% or less, or 27 wt% or less, or 26 wt% or less, or 25 wt% or less, or 24 wt% or less, or 23 wt% or less, or 22 wt% or less, or 21 wt% or less.

[0029] Lithium Carbonate

[0030] Lithium carbonate is included in the slurry. The chemical formula of lithium carbonate is Li 2 CO 3Lithium carbonate can be added to the slurry as a powder, multiple particles, or as an aqueous dispersion. The slurry contains 1 wt% to 10 wt% of lithium carbonate based on the total weight of the slurry. For example, the slurry can contain 1 wt% or more, or 2 wt% or more, or 3 wt% or more, or 4 wt% or more, or 5 wt% or more, or 6 wt% or more, or 7 wt% or more, or 8 wt% or more, or 9 wt% or more of lithium carbonate, and at the same time, 10 wt% or less, or 9 wt% or less, or 8 wt% or less, or 7 wt% or less, or 6 wt% or less, or 5 wt% or less, or 4 wt% or less, or 3 wt% or less, or 2 wt% or less, or 1 wt% or less of lithium carbonate or less.

[0031] Carbon Source

[0032] The slurry can contain one or more carbon sources. The carbon source is selected from the group consisting of carbon black, glucose, carbon nanotubes, graphene, polyethylene glycol, sucrose, and combinations thereof. The slurry contains 5 wt% to 15 wt% of the carbon source based on the total weight of the slurry. For example, the slurry can contain 5 wt% or more, or 6 wt% or more, or 7 wt% or more, or 8 wt% or more, or 9 wt% or more, or 10 wt% or more, or 11 wt% or more, or 12 wt% or more, or 13 wt% or more, or 14 wt% or more of the carbon source, and at the same time, 15 wt% or less, or 14 or less, or 13 wt% or less, or 12 wt% or less, or 11 wt% or less, or 10 wt% or less, or 9 wt% or less, or 8 wt% or less, or 7 wt% or less, or 6 wt% or less of the carbon source or less.

[0033] Water

[0034] The slurry contains water. The slurry may contain 50 wt% to 70 wt% water based on the total weight of the slurry. For example, the slurry may contain 50 wt% or more, or 52 wt% or more, or 54 wt% or more, 56 wt% or more, or 58 wt% or more, or 60 wt% or more, or 62 wt% or more, or 64 wt% or more, 66 wt% or more, or 68 wt% or more of water, while at the same time 70 wt% or less, or 68 wt% or less, or 66 wt% or less, or 64 wt% or less, or 62 wt% or less, or 60 wt% or less, or 58 wt% or less, or 56 wt% or less, or 54 wt% or less, or 52 wt% or less of water. The slurry may be 20 wt% solids to 60 wt% solids (i.e., the sum of the weights of the solid components divided by the total weight of the slurry). For example, the slurry may be 20 wt% or more, or 22 wt% or more, or 24 wt% or more, 26 wt% or more, or 28 wt% or more, or 30 wt% or more, or 32 wt% or more, or 34 wt% or more, 36 wt% or more, or 38 wt% or more, or 40 wt% or more, or 42 wt% or more, or 44 wt% or more, 46 wt% or more, or 48 wt% or more, or 50 wt% or more, or 52 wt% or more, or 54 wt% or more, 56 wt% or more, or 58 wt% or more, while at the same time 60 wt% or less, or 58 wt% or less, or 56 wt% or less, or 54 wt% or less, or 52 wt% or less, or 50 wt% or less, or 48 wt% or less, or 46 wt% or less, or 44 wt% or less, or 42 wt%, or 40 wt% or less, or 38 wt% or less, or 36 wt% or less, or 34 wt% or less, or 32 wt% or less, or 30 wt% or less, or 28 wt% or less, or 26 wt% or less, or 24 wt% or less, or 22 wt% solids.

[0035] Abrasive

[0036] The slurry contains an abrasive. The abrasive has structure (I)

[0037]

[0038] where n in structure (I) is from 1 to 10, and R 1 is selected from the group consisting of hydrogen, an alkylphenyl group, a linear or branched primary alkyl chain or secondary alkyl chain, and R 2 is selected from the group consisting of hydrogen, a methyl group, an ethyl group, or a combination thereof. It should be understood that when R 2When it is not hydrogen, depending on the value of n, Structure (I) may have one or both of a methyl group and an ethyl group. In addition, the combination of such methyl and ethyl groups may be randomly or block-ordered within Structure (I). When R 1 is an alkylphenol, it may be an alkylphenol selected from the group consisting of octylphenyl, nonylphenyl, and combinations thereof. In other examples, R 1 may be C 12 -C 14 secondary alkyl.

[0039] In examples where R 1 is not hydrogen, the total number of carbon atoms in Structure (I) may be from 6 to 18. For example, the total number of carbon atoms in Structure (I) may be 6 or greater, or 7 or greater, or 8 or greater, or 9 or greater, or 10 or greater, or 11 or greater, or 12 or greater, or 13 or greater, or 14 or greater, or 15 or greater, or 16 or greater, or 17 or greater as determined by 13 C nuclear magnetic resonance, while being 18 or less, or 17 or less, or 16 or less, or 15 or less, or 14 or less, or 13 or less, or 12 or less, or 11 or less, or 10 or less, or 9 or less, or 8 or less, or 7 or less.

[0040] The value of n for Structure (I) may be 1 or greater, or 2 or greater, or 3 or greater, or 4 or greater, or 5 or greater, or 6 or greater, or 7 or greater, or 8 or greater, or 9 or greater as determined by 13 C nuclear magnetic resonance, while being 10 or less, or 9 or less, or 8 or less, or 7 or less, or 6 or less, or 5 or less, or 4 or less, or 3 or less, or 2 or less.

[0041] Specific examples of the abrasive include diol octylphenyl ether phosphate (such as Structure (II)), ethoxylated C12-14 secondary alcohol phosphate (such as Structure (III)), and C6-12 ethoxylated and propoxylated alcohol phosphate (such as Structure (IV)).

[0042]

[0043] The slurry contains an abrasive in an amount of 0.1 wt% to 5 wt% based on the total weight of the slurry. For example, the slurry may contain 0.1 wt% or more, or 0.2 wt% or more, or 0.4 wt% or more, or 0.6 wt% or more, or 0.8 wt% or more, or 1.0 wt% or more, or 1.2 wt% or more, or 1.4 wt% or more, or 1.6 wt% or more, or 1.8 wt% or more, or 2.0 wt% or more, or 2.2 wt% or more, or 2.4 wt% or more, or 2.6 wt% or more, or 2.8 wt% or more, or 3.0 wt% or more, or 3.2 wt% or more, or 3.4 wt% or more, or 3.6 wt% or more, or 3.8 wt% or more, or 4.0 wt% or more, or 4.2 wt% or more, or 4.4 wt% or more, or 4.6 wt% or more, or 4.8 wt% or more of the abrasive, and at the same time, 5.0 wt% or less, or 4.8 wt% or less, or 4.6 wt% or less, or 4.4 wt% or less, or 4.2 wt% or less, or 4.0 wt% or less, or 3.8 wt% or less, or 3.6 wt% or less, or 3.4 wt% or less, or 3.2 wt% or less, or 3.0 wt% or less, or 2.8 wt% or less, or 2.6 wt% or less, or 2.4 wt% or less, or 2.2 wt% or less, or 2.0 wt% or less, or 1.8 wt% or less, or 1.6 wt% or less, or 1.4 wt% or less, or 1.2 wt% or less, or 1.0 wt% or less, or 0.8 wt% or less, or 0.6 wt% or less, or 0.4 wt% or less, or 0.2 wt% or less of the abrasive.

[0044] Polyethylene Glycol

[0045] The slurry contains polyethylene glycol. Polyethylene glycol is a compound having structure (V)

[0046] H—(O—CH 2 —CH 2 ) n —OH Structure (V)

[0047] where n refers to the number of repeating units in the polyethylene glycol polymer. The n value of polyethylene glycol can be determined by 13in the range of 10 to 80 as determined by 13C nuclear magnetic resonance. The polyethylene glycol has a weight average molecular weight of from 1,000 grams per mole ("g / mol") to 3,500 g / mol as measured by gel permeation chromatography. For example, the weight average molecular weight of the polyethylene glycol can be 1,000 g / mol or greater, or 1,250 g / mol or greater, or 1,450 g / mol or greater, or 1,500 g / mol or greater, or 1,750 g / mol or greater, or 2,000 g / mol or greater, or 2,250 g / mol or greater, or 2,500 g / mol or greater, or 2,750 g / mol or greater, or 3,000 g / mol or greater, or 3,250 g / mol or greater as measured by gel permeation chromatography, while being 3,500 g / mol or less, or 3,250 g / mol or less, or 3,000 g / mol or less, or 2,750 g / mol or less, or 2,500 g / mol or less, or 2,250 g / mol or less, or 2,000 g / mol or less, or 1,750 g / mol or less, or 1,500 g / mol or less, or 1,250 g / mol or less. Commercially available examples of polyethylene glycol include CARBOWAX from The Dow Chemical Company, Midland, Michigan TM Polyethylene glycol 1450.

[0048] Example

[0049] Materials

[0050] The following materials were used for Comparative Examples ("CE") and Invention Examples ("IE").

[0051] FePO 4 is iron phosphate and is commercially available from Sinopharm Chemical Reagent Co., Ltd., Beijing, China.

[0052] Li 2 CO 3 is lithium carbonate and is commercially available from Sinopharm Chemical Reagent Co., Ltd., Beijing, China.

[0053] Glucose is C 6 H 12 O 6 and is commercially available from Sinopharm Chemical Reagent Co., Ltd., Beijing, China.

[0054] PEG1450 is polyethylene glycol with a weight average molecular weight of 1450 g / mol and is commercially available as CARBOWAX TM Polyethylene glycol 1450 from The Dow Chemical Company, Midland, Michigan.

[0055] MA1 is 100 wt% of the active ingredient of Structure (II) in water and is commercially available from The Dow Chemical Company, Midland, Michigan.

[0056] MA2 is 100 wt% of the active ingredient of Structure (III) in water and is commercially available from The Dow Chemical Company, Midland, Michigan.

[0057] PPA is phosphoric acid with a concentration of 99.7 wt% or higher and is commercially available from Sinopharm Group, Beijing, China.

[0058] SURF1 is a surfactant with Structure (VI)

[0059]

[0060] and is commercially available from The Dow Chemical Company, Midland, Michigan

[0061] MA3 is 100 wt% of the active ingredient of Structure (IV) in water. MA3 is synthesized through the following steps. First, 58 grams of SURF1 is placed in a three-necked flask under N 2 atmosphere and heated to 35 °C while mechanically stirring at 300 rpm. The mechanical stirring remains constant during the formation of MA3. Then, 10.69 grams of PPA is added dropwise to the flask over ten minutes to form a solution. After the addition of PPA is complete, the temperature is raised to 45 °C and the system is further stirred for 30 minutes. Then, the temperature is raised to 80 °C and the system is stirred for another 3.5 hours. Then, the solution turns yellow and 1 mL of water is added to accelerate hydrolysis. Then, the solution is cooled to 65 °C and stirred for another 10 hours to complete hydrolysis. Then, the solution is cooled to 23 °C.

[0062] Sample Preparation

[0063] The example and comparative example LFP slurries of the present invention are prepared according to the following procedure and have the compositions shown in Table 1 in wt%. First, the abrasives used (i.e., MA1, MA2, and MA3) are dried in an oven at 80 °C for 24 hours. Then, FePO 4 and Li 2 CO 3 are dispersed in water and mixed using a SPEEDMIXER TM DAC 150 mixer at 1200 rpm for 2 minutes to form a system. Then, glucose is added to the system and mixed at 1200 rpm until completely dissolved. Then, the indicated amount of abrasive is added to the system and mixed at 1200 rpm until completely dissolved.

[0064] Table 1

[0065]

[0066]

[0067] Testing Method

[0068] Grinding : Grinding was carried out in a 215 ml grinding tank with an inner diameter of 5 cm. Zirconium beads (0.8 mm - 1.2 mm in diameter) and slurry with a mass ratio of 1:1 were added to the grinding tank. The grinding tank was run at 1400 rpm for 8 hours. The grinding tank was stopped every 2 hours, and 0.2 ml of slurry sample was taken for particle size characterization.

[0069] Particle Size Testing : Using the ZEN3600 from Malvern Panalytical TM particle size analyzer to measure the particle size. The sample was diluted 20 times with water for measurement. The refractive indices of the material and water were set to 1.71 and 1.33 respectively. The temperature was 25 °C.

[0070] Results

[0071] Table 2 provides the grinding results of the examples and comparative examples of the present invention.

[0072] Table 2

[0073] Example 2 hours 4 hours 6 hours 8 hours CE1 561.2 434.9 377.4 347.6 CE2 589.3 445.2 408.3 349.9 IE1 529.1 400.7 331.6 308.3 IE2 462.7 351.9 312.7 314.2 IE3 530.0 402.6 343.7 323.9 IE4 487.9 373.9 322.5 301.5 IE5 520.6 380.0 342.4 310.8 IE6 508.7 398.8 354.2 313.4

[0074] Now referring to Table 1 and Table 2, glucose and glucose plus PEG were set as comparative examples because they represent materials conventionally used in the grinding of LFP slurry. It can be seen that within 4 hours of grinding, glucose and PEG did not approach the target particle size of 1% within 400 nm (i.e., 404 nm) or smaller. Specifically, for CE1, it took until 6 hours of grinding to achieve a size of 400 nm or smaller, while CE2 still could not achieve this target.

[0075] Now referring to IE1 - IE6, the use of the abrasive with structure (I) clearly achieved the target particle size of 1% within 400 nm (i.e., 404 nm) or smaller within 4 hours of grinding. As described above, it is believed that the phosphate group of structure (I) is responsible for increasing the affinity of the abrasive for iron phosphate of the LFP precursor. At the same time, the ethylene oxide and / or ethylene oxide / propylene oxide segments of the abrasive are responsible for improving the affinity of the abrasive for water. By effectively coupling water and iron phosphate, the abrasive can accelerate the dispersion of the raw materials, which increases the grinding efficiency, thus achieving a smaller LFP particle size faster than that provided by conventional materials. In addition to saving time and money associated with the grinding process, the abrasive of the present invention has the additional benefit of not introducing heteroatoms into the slurry.

Claims

1. A grinding method, the grinding method comprises the following steps: Combine FePO 4 、 Li 2 CO 3 with water, a carbon source, and an abrasive to form a slurry, wherein the abrasive of the slurry has structure (I) wherein n of structure (I) is from 1 to 10, and R 1 is selected from the group consisting of hydrogen, an alkylphenyl group, a linear or branched primary or secondary alkyl chain, and R 2 is selected from the group consisting of hydrogen, a methyl group, an ethyl group, or a combination thereof; and Grind the slurry.

2. The method according to claim 1, wherein the step of grinding the slurry further comprises: Grind the slurry for 4 hours to obtain Slurry D with a particle size of 404 nm or less as measured according to particle size testing 50 Particle size.

3. The method according to any one of claims 1 and 2, wherein the step of combining FePO 4 , Li 2 CO 3 , water, a carbon source, and an abrasive to form a slurry is further comprises: Combine the FePO 4 , the Li 2 CO 3 , the water, the carbon source, the abrasive and polyethylene glycol to form the slurry.

4. The method according to any one of claims 1 to 3, wherein the carbon source is glucose.

5. The method according to any one of claims 1 to 4, wherein R of structure (I) 2 is hydrogen.

6. The method according to claim 5, wherein R 1 is not hydrogen and the total number of carbon atoms in structure (I) is from 6 to 18.

7. The method according to claim 5, wherein R 1 is an alkylphenol selected from the group consisting of octylphenyl, nonylphenyl, and combinations thereof.

8. The method according to claim 5, wherein R 1 is C 12 -C 14 secondary alkyl group.

9. The method according to any one of claims 1 to 8, wherein the slurry comprises: 20 wt% to 30 wt% of the FePO based on the total weight of the slurry 4 ; 1 wt% to 10 wt% of said Li based on the total weight of the slurry 2 CO 3 ; 5% to 15% by weight of the carbon source based on the total weight of the slurry; 50% to 70% by weight of water based on the total weight of the slurry; and 0.1% to 5% by weight of an abrasive based on the total weight of the slurry.

10. The method according to any one of claims 1 to 9, wherein the slurry comprises 1% to 2% by weight of the abrasive based on the total weight of the slurry.

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