EP4595126A1

EP4595126A1 - Phosphoric milling agents and methods of use

Info

Publication number: EP4595126A1
Application number: EP22801970.9A
Authority: EP
Inventors: Qinyuan GUI; Peng Gao; Cheng Shen; Meijia HE
Original assignee: Dow Global Technologies LLC
Current assignee: Dow Global Technologies LLC
Priority date: 2022-10-26
Filing date: 2022-10-26
Publication date: 2025-08-06
Also published as: TW202434691A; JP2026510173A; WO2024087057A1; CN120077492A; KR20250093537A

Abstract

A milling method includes the steps of combining FePO ₄, Li ₂CO ₃, water, a carbon source and a milling agent to form a slurry, the milling agent of the slurry having Structure (I), wherein n of Structure (I) is from 1 to 10 and R ₁ is selected from the group consisting of hydrogen, alkylphenyl group, linear or branched primary or secondary alkyl chain and R ₂ is selected from the group consisting of a hydrogen, methyl group, an ethyl group or combinations thereof; and milling the slurry.

Description

PHOSPHORIC MILLING AGENTS AND METHODS OF USE

BACKGROUND

Field of the disclosure
The present disclosure relates to milling agents, and more specifically to methods of using phosphoric milling agents.
Introduction
The rise of battery powered consumer electronics, and now vehicles, has greatly increased demand for lithium-ion batteries and the products used in the manufacture of such batteries. Within each lithium-ion battery exists a cathode which is typically composed LiFePO ₄ ( “LFP” ) . Industrial fabrication of LFP is accomplished through a variety of processes, but the most popular is solid phase synthesis. Solid phase synthesis of LFP involves a number of steps. In a first step of making the LFP, raw materials (FePO ₄, Li ₂CO ₃, a carbon source and a milling agent) are dispersed into water and sand milled until a raw material particle size of the resulting slurry reaches a D ₅₀ of approximately 400 nm or less. Next, the slurry is spray dried to get aggregated particles of the mixed raw materials. The resulting spray dried particle size should exhibit have a D ₅₀ of approximately 10 μm. Finally, the spray dried LFP particles are calcined under an N ₂ atmosphere. From there the LFP can be fabricated into cathodes for battery manufacture.
One of the most time-consuming process in the fabrication of LFP is the milling time of the raw ingredients. Milling of the raw ingredients of the LFP can take upwards of 8 hours to reach the desired D ₅₀ particle size. During the milling process, a milling agent is used to help disperse the solid raw materials to increase the milling efficiency. High efficiency of sand milling means less milling time, which will lead to higher production efficiency, lower cost, and better sustainability. Therefore, utilizing a milling agent with high performance can greatly accelerate the development of LFP. A milling agent that achieves a particle size within 1%of 400 nm (i.e., 404 nm) or less within 4 hours of milling would drastically improve the efficiency of the milling process.
The selection of materials used and when the materials are used in the fabrication of LFP and LFP based cathodes comes with added considerations given the electrochemical nature of batteries. For example, most milling agents are surfactants like sodium dodecyl sulfate ( “SDS” ) , hexadecyl trimethyl ammonium Bromide ( “CTAB” ) , and polyethylene glycol (PEG) . However, for SDS and CTAB, the heteroatoms present in such milling agents, such as S, N, and Br, will greatly lower the electrochemical stability of LFP cathodes. Furthermore, metal ions, for example Na ⁺, will interfere with the transport of Li ⁺ and greatly affect the electrical performance of LFP. As such, materials which have been neutralized with alkali atoms, like those provided in JP2014149968A, should be avoided because such neutralization introduces undesirable heteroatoms. Ideally, a milling agent should introduce no detectable S, N, Br, and metal ions to the LFP slurry.
In view of the foregoing, it would be surprising and advantageous to discover a milling agent and method that not only achieves a particle size within 1%of 400 nm (i.e., 404 nm) or less within 4 hours of milling, but also introduces no S, N, Br, and metal ions to the LFP slurry.
SUMMARY OF THE DISCLOSURE
The inventors of the present disclosure have discovered a milling agent and method that not only achieves a particle size within 1%of 400 nm (i.e., 404 nm) or less within 4 hours of milling, but also introduces no S, N, Br, and metal ions to the LFP slurry.
The disclosure is a result of discovering that by utilizing a milling agent comprising a non-neutralized phosphoric acid moiety, the affinity between the FePO ₄ and the milling agent can be increased. It has been found that the increased affinity between the milling agent including a phosphoric acid moiety and the FePO ₄ allows the FePO ₄ to be milled within 1%of 400 nm faster than traditional milling agents. Further, by utilizing a non-neutralized phosphoric acid moiety in the milling agent, the milling agent donates no hetero atoms to the LFP slurry and any resulting products. As a result, use of the inventive milling agent in the milling process not only saves time and energy in the milling, but also avoids contaminating the LFP slurry the way traditional milling agents do.
According to a first feature of the present disclosure, a milling method comprises the steps of combining FePO ₄, Li ₂CO ₃, water, a carbon source and a milling agent to form a slurry, the milling agent of the slurry having Structure (I) , wherein n of Structure (I) is from 1 to 10 and R ₁ is selected from the group consisting of hydrogen, alkylphenyl group, linear or branched primary or secondary alkyl chain and R ₂ is selected from the group consisting of a hydrogen, methyl group, an ethyl group or combinations thereof; and milling the slurry.
According to a second feature of the present disclosure, the step of milling the slurry further comprises milling 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.
According to a third feature of the present disclosure, the step of combining FePO ₄, Li ₂CO ₃, water, a carbon source and a milling agent to form a slurry further comprises combining the FePO ₄, the Li ₂CO ₃, the water, the carbon source, the milling agent and polyethylene glycol to form the slurry.
According to a fourth feature of the present disclosure, the carbon source is glucose.
According to a fifth feature of the present disclosure, R ₂ of Structure (I) is a hydrogen.
According to a sixth feature of the present disclosure, R ₁ is not a hydrogen and a total number of carbon atoms in Structure (I) is from 6 to 18.
According to a seventh feature of the present disclosure, R ₁ is an alkylphenol selected from the group consisting of octyl phenyl, nonyl phenyl and combinations thereof.
According to an eighth feature of the present disclosure, R ₁ is a C ₁₂-C ₁₄ secondary alkyl.
According to a ninth feature of the present disclosure, slurry comprises 20 wt%to 30 wt%of the FePO ₄ based on a total weight of the slurry; 1 wt%to 10 wt%of the Li ₂CO ₃ based on a total weight of the slurry; 5 wt%to 15 wt%of the carbon source based on a total weight of the slurry; 50 wt%to 70 wt%water based on a total weight of the slurry; and 0.1 wt%to 5 wt%of milling agent based on a total weight of the slurry.
According to a tenth feature of the present disclosure, the slurry comprises from 1 wt%to 2 wt%of the milling agent based on a total weight of the slurry.

DETAILED DESCRIPTION

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 employed by itself, or any combination of two or more of the listed items can be employed. 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.
All ranges include endpoints unless otherwise stated.
Test methods refer to the most recent test method as of the priority date of this document unless a date is indicated with the test method number as a hyphenated two-digit number. References to test methods contain both a reference to the testing society and the test method number. Test method organizations are referenced by one of the following abbreviations: ASTM refers to ASTM International (formerly known as American Society for Testing and Materials) ; IEC refers to International Electrotechnical Commission; EN refers to European Norm; DIN refers to Deutsches Institut für Normung; and ISO refers to International Organization for Standards.
As used herein, the term weight percent ( “wt%” ) designates the percentage by weight a component is of a total weight of the polymeric composition unless otherwise specified.
As used herein, Chemical Abstract Services registration numbers ( “CAS#” ) refer to the unique numeric identifier as most recently assigned as of the priority date of this document to a chemical compound by the Chemical Abstracts Service.
Method
The present disclosure is directed to a milling method. The method comprises the steps of combining FePO ₄, Li ₂CO ₃, water, a carbon source and a milling agent to form a slurry and milling the slurry. The milling of the slurry may be carried out in a bead mill, a sand mill, a basket mill, or other type of mill configured to grind particles in a slurry to a small and uniform size using a grinding media. The grinding media (i.e., beads, sand, etc. ) are typically spherical and have a diameter from 0.1 mm to 5 mm in size. The grinding media is harder than the constituents of the slurry which it is grinding. During milling, the slurry and grinding media may be rotated, tumbled, shaken or otherwise agitated to induce grinding of the slurry. In examples where the milling is accomplished through rotation, the mill may be rotated at a speed of 500 revolutions per minute ( “rpm” ) to 2000 rpm. The milling of the slurry may be carried out for a period of 1 hour or greater, or 2 hours or greater, or 3 hours or greater, or 4 hours or greater, or 5 hours or greater, or 6 hours or greater, or 7 hours or greater, or 8 hours or greater, or 9 hours or greater, while at the same time, 10 hours or less, or 9 hours or less, or 8 hours or less, or 7 hours or less, or 6 hours or less, or 5 hours or less, or 4 hours or less, or 3 hours or less, or 2 hours or less.
Milling of the slurry is performed for a period of time until the particles of the FePO ₄ and Li ₂CO ₃ reach a desired D ₅₀ particle size. A D ₅₀ particle size is the median particle size of a distribution and indicates 50%by volume of 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 according to Particle Size Testing as explained in greater 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 according to Particle Size Testing.
Ferric Phosphate
Ferric phosphate is included in the slurry. Ferric phosphate has a chemical formula of FePO ₄. Ferric phosphate may be added to the slurry as a powder, a plurality of particles or as an aqueous dispersion. The slurry comprises from 20 wt%to 30 wt%of the FePO ₄ based on a total weight of the slurry. For example, the slurry can comprise 20 wt%or greater, or 21 wt%or greater, or 22 wt%or greater, or 23 wt%or greater, or 24 wt%or greater, or 25 wt%or greater, or 26 wt%or greater, or 27 wt%or greater, or 28 wt%or greater, or 29 wt%or greater, while 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 of the ferric phosphate or less based on a total weight of the slurry.
Lithium Carbonate
Lithium carbonate is included in the slurry. Lithium carbonate has a chemical formula of Li ₂CO ₃. Lithium carbonate may be added to the slurry as a powder, a plurality of particles or as an aqueous dispersion. The slurry comprises from 1 wt%to 10 wt%of the lithium carbonate based on a total weight of the slurry. For example, the slurry can comprise 1 wt%or greater, or 2 wt%or greater, or 3 wt%or greater, or 4 wt%or greater, or 5 wt%or greater, or 6 wt%or greater, or 7 wt%or greater, or 8 wt%or greater, or 9 wt%or greater, while 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 the lithium carbonate or less based on a total weight of the slurry.
Carbon Source
The slurry may comprise 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 comprises from 5 wt%to 15 wt%of the carbon source based on a total weight of the slurry. For example, the slurry can comprise 5 wt%or greater, or 6 wt%or greater, or 7 wt%or greater, or 8 wt%or greater, or 9 wt%or greater, or 10 wt%or greater, or 11 wt%or greater, or 12 wt%or greater, or 13 wt%or greater, or 14 wt%or greater, while 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 based on a total weight of the slurry.
Water
The slurry comprises water. The slurry may comprise from 50 wt%to 70 wt%water based on a total weight of the slurry. For example, the slurry may comprise 50 wt%or greater, or 52 wt%or greater, or 54 wt%or greater, of 56 wt%or greater, or 58 wt%or greater, or 60 wt%or greater, or 62 wt%or greater, or 64 wt%or greater, of 66 wt%or greater, or 68 wt%or greater, 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 based on a total weight of the slurry. The slurry may be from 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 greater, or 22 wt%or greater, or 24 wt%or greater, of 26 wt%or greater, or 28 wt%or greater, or 30 wt%or greater, or 32 wt%or greater, or 34 wt%or greater, of 36 wt%or greater, or 38 wt%or greater, or 40 wt%or greater, or 42 wt%or greater, or 44 wt%or greater, of 46 wt%or greater, or 48 wt%or greater, or 50 wt%or greater, or 52 wt%or greater, or 54 wt%or greater, of 56 wt%or greater, or 58 wt%or greater, 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.
Milling Agent
The slurry comprises the milling agent. The milling agent has Structure (I)
wherein n of Structure (I) is from 1 to 10 and R ₁ is selected from the group consisting of hydrogen, alkylphenyl group, linear or branched primary or secondary alkyl chain and R ₂ is selected from the group consisting of a hydrogen, a methyl group, an ethyl group or combinations thereof. It will be understood that when R ₂ is not a hydrogen, Structure (I) may have one or both of a methyl group and an ethyl group depending on the value of n. Further, such combinations of methyl and ethyl groups may be in a random or block ordering 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 yet other examples, R ₁ may be a C ₁₂-C ₁₄ secondary alkyl.
In examples where R ₁ is not a hydrogen, a 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, while at the same time, 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 as determined by ¹³C nuclear magnetic resonance.
The n value of 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, while at the same time, 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 as determined by ¹³C nuclear magnetic resonance.
Specific examples of the milling agent include a glycol octylphenyl ether phosphoric acid such as Structure (II) , an ethoxylated C12-14 secondary alcohol phosphoric acid such as Structure (III) and a C6-12 ethoxylated and propoxylated alcohol phosphoric acid such as Structure (IV) .
The slurry comprises from 0.1 wt%to 5 wt%of the milling agent based on a total weight of the slurry. For example, the slurry may comprise 0.1 wt%or greater, or 0.2 wt%or greater, or 0.4 wt%or greater, or 0.6 wt%or greater, or 0.8 wt%or greater, or 1.0 wt%or greater, or 1.2 wt%or greater, or 1.4 wt%or greater, or 1.6 wt%or greater, or 1.8 wt%or greater, or 2.0 wt%or greater, or 2.2 wt%or greater, or 2.4 wt%or greater, or 2.6 wt%or greater, or 2.8 wt%or greater, or 2.0 wt%or greater, or 3.2 wt%or greater, or 3.4 wt%or greater, or 3.6 wt%or greater, or 3.8 wt%or greater, or 4.0 wt%or greater, or 4.2 wt%or greater, or 4.4 wt%or greater, or 4.6 wt%or greater, or 4.8 wt%or greater, while 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 milling agent based on the total weight of the slurry.
Polyethylene Glycol
The slurry comprises polyethylene glycol. Polyethylene glycol is a compound having Structure (V)
H- (O-CH ₂-CH ₂) _n-OH Structure (V)
where n refers to the number of repeat units in the polyethylene glycol polymer. The n value for the polyethylene glycol may be in a range from 10 to 80 as determined by ¹³C nuclear magnetic resonance. The polyethylene glycol has a weight average molecular weight from 1000 grams per mol ( “g/mol” ) to 3500 g/mol as measured according to gel permeation chromatography. For example, the weight average molecular weight of the polyethylene glycol may be 1000 g/mol or greater, or 1250 g/mol or greater, or 1450 g/mol or greater, or 1500 g/mol or greater, or 1750 g/mol or greater, or2000 g/mol or greater, or 2250 g/mol or greater, or 2500 g/mol or greater, or 2750 g/mol or greater, or 3000 g/mol or greater, or 3250 g/mol or greater, while at the same time, 3500 g/mol or less, or 3250 g/mol or less, or 3000 g/mol or less, or 2750 g/mol or less, or 2500 g/mol or less, or 2250 g/mol or less, or 2000 g/mol or less, or 1750 g/mol or less, or 1500 g/mol or less, or 1250 g/mol or less as measured according to gel permeation chromatography. A Commercially available example of polyethylene glycol includes CARBOWAX ^TM Polyethylene Glycol 1450 from The Dow Chemical Company, Midland, Michigan.
Examples
Materials
The following materials were used in the comparative examples ( “CE” ) and the inventive examples ( “IE” ) .
FePO ₄ is ferric phosphate and is commercially available from Sinopharm, Beijing, China.
Li ₂CO ₃ is lithium carbonate and is commercially available from Sinopharm, Beijing, China.
Glucose is C ₆H ₁₂O ₆ and is commercially available from Sinopharm, Beijing, China.
PEG1450 is polyethylene glycol having a weight average molecular weight of 1, 450 g/mol and is commercially available as CARBOWAX ^TM Polyethylene Glycol 1450 from The Dow Chemical Company, Midland, Michigan.
MA1 is 100 wt%Structure (II) actives in water and is commercially available as from The Dow Chemical Company, Midland, Michigan.
MA2 is 100 wt%Structure (III) actives in water and is commercially available from The Dow Chemical Company, Midland, Michigan.
PPA is phosphoric acid having an 99.7 wt%or greater concentration which is commercially available Sinopharm, Beijing, China.
SURF1 is a surfactant having structure (VI)
which is commercially available from The Dow Chemical Company, Midland, Michigan
MA3 is 100 wt%Structure (IV) actives in water. MA3 is synthesized by the following procedure. First, 58 grams of SURF1 was put in a three-necked flask under N ₂ atmosphere and heated to 35℃ under while mechanical stirred at 300 rpm. The mechanical agitation remained constant during the formation of MA3. Next, 10.69 grams of PPA was added into the flask dropwise over ten minutes to form a solution. After addition of the PPA was complete, the temperature was raised to 45℃ and the system was further stirred for 30 minutes. Next, the temperature was raised to 80℃ and the system was stirred for another 3.5 hours. Next, the solution turned yellow and 1 mL of water was added to accelerate hydrolysis. Next, the solution was cooled to 65℃ and stirred for another 10 hours to allow complete hydrolysis. Next, the solution was allowed to cool to 23℃.
Sample preparation
The inventive and comparative example LFP slurries were prepared according to the following procedure and have the composition in wt%indicated in Table 1. First, the milling agents used (ie., MA1, MA2 and MA3) were dried in an oven at 80° for 24 hours. Next, FePO ₄ and Li ₂CO ₃ were dispersed into water and mixed at 1200 rpm for 2 minutes using a SPEEDMIXER ^TM DAC 150 mixer to form a system. Next, glucose was added into the system and mixed at 1200 rpm until completely dissolved. Next, the indicated amount of milling agent was added to the system and mixed at 1200 rpm until completely dissolved.
Table 1

	H ₂O	FePO ₄	Li ₂CO ₃	Glucose	PEG1450	MA1	MA2	MA3
CE1	60	25.7	6.3	8	0	0	0	0
CE2	60	25.7	6.3	6	2	0	0	0
IE1	60	25.7	6.3	6	0	2		0
IE2	60	25.7	6.3	6	0		2	0
IE3	60	25.7	6.3	6	0		0	2
IE4	60	25.7	6.3	6	1	1	0	0
IE5	60	25.7	6.3	6	1	0	1	0
IE6	60	25.7	6.3	6	1	0	0	1

Test Methods
Milling: Milling was performed in a 215 ml milling tank having an inner diameter of 5 cm. A 1: 1 mass ratio of zirconium beads (0.8～1.2 mm in diameter) and slurry was added into the milling tank. The milling tank was operated a 1400 rpm for 8 hours. Every 2 hours the milling tank was stopped and a 0.2 ml sample of the slurry was retrieved for particle size characterization.
Particle Size Testing: Particle size was measured using a ZEN3600 ^TM particle size analyzer from Malvern Pananalytical. The sample was diluted 20 times with water for the measurement. The refraction index of material and water were set as 1.71 and 1.33 respectively. The temperature was 25℃.
Results
Table 2 provides the results of the milling for the inventive and comparative examples.
Table 2

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

Referring now to Tables 1 and 2, glucose and glucose plus PEG were set as the comparative examples as they represent traditionally used materials in the milling of LFP slurries. As can be seen, glucose and PEG do not come close to achieving the targeted particle size within 1%of 400 nm (i.e., 404 nm) or less within 4 hours of milling. Specifically, it took until the 6 hours of milling for CE1 to achieve a 400nm or less size with CE2 still failing to achieve the target.
Referring now to IE1-IE6, the use of a milling agent having Structure (I) clearly achieves the targeted particle size within 1%of 400 nm (i.e., 404 nm) or less within 4 hours of milling. As explained above, it is believed that the phosphoric acid group of Structure (I) is responsible for increasing the affinity of the milling agent with the ferric phosphate of the LFP precursor. Simultaneously, the ethylene oxide and/or ethylene oxide/propylene oxide segments of the milling agents are responsible for the enhancing the affinity of the milling agent with water. By effectively coupling the water and the ferric phosphate, the milling agent is able to accelerate the dispersion of the raw materials which increases the milling efficiency thereby achieving a smaller LFP particle size faster than provided by the conventional materials. In addition to saving time and money related to the milling process, the inventive milling agents have the added benefit of introducing no heteroatoms to the slurry.

Claims

A milling method, comprising the steps of:

combining FePO ₄, Li ₂CO ₃, water, a carbon source and a milling agent to form a slurry, the milling agent of the slurry having Structure (I)

wherein n of Structure (I) is from 1 to 10 and R ₁ is selected from the group consisting of hydrogen, alkylphenyl group, linear or branched primary or secondary alkyl chain and R ₂ is selected from the group consisting of a hydrogen, methyl group, an ethyl group or combinations thereof; and

milling the slurry.
The method of claim 1, wherein the step of milling the slurry further comprises:

milling 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.
The method of any one of claims 1 and 2, wherein the step of combining FePO ₄, Li ₂CO ₃, water, a carbon source and a milling agent to form a slurry further comprises:

combining the FePO ₄, the Li ₂CO ₃, the water, the carbon source, the milling agent and polyethylene glycol to form the slurry.
The method of any one of claims 1-3, wherein the carbon source is glucose.
The method of any one of claims 1-4, wherein R ₂ of Structure (I) is a hydrogen.
The method of claim 5, wherein R ₁ is not a hydrogen and a total number of carbon atoms in Structure (I) is from 6 to 18.
The method of claim 5, wherein R ₁ is an alkylphenol selected from the group consisting of octyl phenyl, nonyl phenyl and combinations thereof.
The method of claim 5, wherein R ₁ is a C ₁₂-C ₁₄ secondary alkyl.
The method of any of claims 1-8, wherein the slurry comprises:

20 wt%to 30 wt%of the FePO ₄ based on a total weight of the slurry;

1 wt%to 10 wt%of the Li ₂CO ₃ based on a total weight of the slurry;

5 wt%to 15 wt%of the carbon source based on a total weight of the slurry;

50 wt%to 70 wt%water based on a total weight of the slurry; and

0.1 wt%to 5 wt%of milling agent based on a total weight of the slurry.
The method of any one of claims 1-9, wherein the slurry comprises from 1 wt%to 2 wt%of the milling agent based on a total weight of the slurry.