High power electrode materials

• US 9,954,228 B2
• Filed: 07/27/2016
• Issued: 04/24/2018
• Est. Priority Date: 09/18/2009
• Status: Active Grant

• Current Assignee: A123 Systems Incorporated
• Original Assignee: A123 Systems Incorporated
• Inventors: Beck, Larry, Wilson, Jennifer, Xu, Chuanjing, Shi, Zhong-You, Hammoud, Maha
• Primary Examiner(s): Mayes, Melvin C.
• Assistant Examiner(s): Forrest, Michael
• Application Number:
  US15/221,228
• Publication Number:
  US 20160380269A1
• Time in Patent Office: 636 Days
• CPC Class Codes: C01B 25/375 of iron
• CPC Class Codes: C01B 25/45 containing plural metal, or metal and ammonium
• CPC Class Codes: C01B 25/451 containing metal and ammonium
• CPC Class Codes: C01P 2002/74 by peak-intensities or a ratio thereof only
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/24 Nanoplates, i.e. plate-like particles with a thickness from 1-100 nanometer
• CPC Class Codes: C01P 2004/32 Spheres
• CPC Class Codes: C01P 2004/61 Micrometer sized, i.e. from 1-100 micrometer
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2006/11 Powder tap density
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 2300/0025 Organic electrolyte
• CPC Class Codes: H01M 2300/0028 characterised by the solvent
• CPC Class Codes: H01M 4/136 Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
• CPC Class Codes: H01M 4/5825 Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
• CPC Class Codes: H01M 4/587 for inserting or intercalating light metals
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

An LFP electrode material is provided which has improved impedance, power during cold cranking, rate capacity retention, charge transfer resistance over the current LFP based cathode materials. The electrode material comprises crystalline primary particles and secondary particles, where the primary particle is formed from a plate-shaped single-phase spheniscidite precursor and a lithium source. The LFP includes an LFP phase behavior where the LFP phase behavior includes an extended solid-solution range.

Claims

1. A method to form an ammonium iron phosphate for use to make an electrode active material, comprising:

(a) introducing an iron (II) salt, a phosphate source, an ammonium source, and an oxidizing agent into an aqueous solution to form a mixture;

(b) filtering the mixture to recover a solid by-product;

(c) re-dispersing the solid by-product into an aqueous solution;

(d) heating the aqueous solution;

(e) filtering the solution to recover a solid; and

(f) drying the solid to obtain a high purity spheniscidite with a formula of NH₄Fe₂(PO₄)₂OH.2H₂O.

2. The method of claim 1, wherein the high purity spheniscidite is a single-phase.

3. The method of claim 1, wherein the high purity spheniscidite has a plate-shape morphology.

4. The method of claim 1, wherein the iron (II) salt is selected from iron (II) sulfate, iron (II) chloride, iron (II) nitrate, any hydrate thereof, or a mixture thereof.

5. The method of claim 1, wherein the phosphate source is selected from H₃PO₄, P₂O₅, NH₄H₂PO₄, (NH₄)₂HPO₄, (NH₄)₃PO₄, NaH₂PO₄, Na₂HPO₄, Na₃PO₄, or mixtures thereof.

6. The method of claim 1, wherein the ammonium source is selected from NH₄H₂PO₄, (NH₄)₂HPO₄, (NH₄)₃PO₄, NH₄OH or mixtures thereof.

7. The method of claim 1, wherein the oxidizing agent is selected from H₂O₂, Na₂O, NaClO₃, or mixtures thereof.

8. The method of claim 1, further comprising rinsing the solid by-product and/or solid following filtering.

9. The method of claim 1, further comprising:

(g) mixing the obtained high purity spheniscidite, a lithium source, a dopant, and a carbon source;

(h) adding a solvent to produce a slurry;

(i) milling the slurry;

(j) drying the milled slurry; and

(k) firing the dried milled slurry to obtain the lithium iron phosphate, wherein the lithium iron phosphate comprises a substantially olivine crystalline phase, a primary particle in the range of 20 nm to 80 nm, a secondary particle with d50 in the range of 5 μ

m to 13 μ

m, and a surface area of 25 m²/g to 35 m²/g, and less than 5% by weight of carbon; and

wherein the lithium iron phosphate improves battery performance at low temperatures in comparison to current lithium iron phosphate materials.

10. The method of claim 9, wherein the slurry is milled to obtain primary particles of about 20 nm to about 80 nm.

11. The method of claim 9, wherein the solvent is water.

12. The method of claim 9, wherein the solvent is a compound comprising an alcohol functional group or water.

13. The method of claim 9, wherein the testing at low temperatures are at 0°

C. or lower.

14. The method of claim 9 having a carbon percentage of at least 2.1%.

15. The method of claim 9 having a carbon percentage of about 2.1% to 2.5%.

27. The method of claim 14, wherein the testing at low temperatures are at 0°

C. or lower.

16. A method to form crystalline spheniscidite material for use as an electrode active material, comprising:

(a) introducing an iron (II) salt, a phosphate source, an ammonium source, and an oxidizing agent into an aqueous solution to form a mixture;

(b) filtering the mixture to recover a solid by-product;

(c) re-dispersing the solid by-product into an aqueous solution;

(d) heating the aqueous solution;

(e) filtering the solution to recover a solid; and

(f) drying the solid to obtain a high purity spheniscidite with a formula of NH₄Fe₂(PO₄)₂OH.2H₂O, wherein the crystalline spheniscidite material is an ammonium iron phosphate substantially free of impurities; and

wherein the crystalline spheniscidite material has a plate-shape morphology.

17. The method of claim 16, wherein the high purity spheniscidite is a single-phase.

18. The method of claim 16, wherein the iron (II) salt is selected from iron (II) sulfate, iron (II) chloride, iron (II) nitrate, any hydrate thereof, or a mixture thereof.

19. The method of claim 16, wherein the phosphate source is selected from H₃PO₄, P₂O₅, NH₄H₂PO₄, (NH₄)₂HPO₄, (NH₄)₃PO₄, NaH₂PO₄, Na₂HPO₄, Na₃PO₄, or mixtures thereof.

20. The method of claim 16, wherein the ammonium source is selected from NH₄H₂PO₄, (NH₄)₂HPO₄, (NH₄)₃PO₄, NH₄OH or mixtures thereof.

21. The method of claim 16, wherein the oxidizing agent is selected from H₂O₂, Na₂O, NaClO₃, or mixtures thereof.

22. The method of claim 16, further comprising rinsing the solid by-product and/or solid following filtering.

23. The method of claim 16, further comprising:

(g) mixing the obtained high purity spheniscidite, a lithium source, a dopant, and a carbon source;

(h) adding a solvent to produce a slurry;

(i) milling the slurry;

(j) drying the milled slurry; and

(k) firing the dried milled slurry to obtain the lithium iron phosphate, wherein the lithium iron phosphate comprises a substantially olivine crystalline phase, a primary particle in the range of 20 nm to 80 nm, a secondary particle with d50 in the range of 5 μ

m to 13 μ

m, and a surface area of 25 m²/g to 35 m²/g, a carbon percentage of at least 2.1%; and

wherein the lithium iron phosphate improves battery performance at low temperatures in comparison to current lithium iron phosphate materials.

24. The method of claim 23, wherein the slurry is milled to obtain primary particles of about 20 nm to about 80 nm.

25. The method of claim 23 wherein the solvent is water.

26. The method of claim 23, wherein the solvent is a compound comprising an alcohol functional group or water.

28. A method for synthesizing ammonium iron phosphate for use as an electrode active material in an electrochemical cell, comprising:

introducing an iron (II) salt, a phosphate source, an ammonium source, and an oxidizing agent into an aqueous solution to form a mixture;

filtering the mixture to recover a solid by-product;

re-dispersing the solid by-product into an aqueous solution;

heating the aqueous solution at a temperature in a range of 85-95°

C.;

filtering the solution to recover a solid;

drying the solid to obtain a high purity spheniscidite with a formula of NH₄Fe₂(PO₄)₂OH.2H₂O having a surface area in a range of 20-25 m²/g.

29. The method of claim 28, wherein the high purity spheniscidite has an XRD with no impurity peaks over 5%.

30. The method of claim 28, wherein the high purity spheniscidite comprises:

ammonium in a first range of 4.6-5.0 wt. %, iron in a second range of 30-35 wt. %, and phosphorus in a third range of 15-20 wt. %.

31. The method of claim 30, wherein the high purity spheniscidite has a molar ratio of ammonium to phosphorus of 1.8:

3.5, and a molar ratio of phosphorus to iron of 1;

1.25.

32. The method of claim 28, wherein the aqueous solution of the re-dispersed solid by-product has a pH ranging from 1.8 to 3.1.

33. The method of claim 28, further comprising selecting the iron (II) salt from iron (II) sulfate, iron (II) chloride, iron (II) nitrate, any hydrate thereof, or a mixture thereof.

34. The method of claim 28, further comprising selecting the phosphate source from H₃PO₄, P₂O₅, NH₄H₂PO₄, (NH₄)₂HPO₄, (NH₄)₃PO₄, NaH₂PO₄, Na₂HPO₄, Na₃PO₄, or mixtures thereof.

35. The method of claim 28, further comprising selecting the ammonium source from NH₄H₂PO₄, (NH₄)₂HPO₄, (NH₄)₃PO₄, NH₄OH or mixtures thereof.

36. The method of claim 28, further comprising selecting the oxidizing agent from H₂O₂, Na₂O, NaClO₃, or mixtures thereof.

37. The method of claim 28, wherein the high purity spheniscidite has an XRD with no impurity peaks over 5%.

38. The method of claim 28, wherein the high purity spheniscidite has a surface area of 20-25 m₂/g.

39. The method of claim 28, wherein the high purity spheniscidite has a plate-shape morphology.

40. The method of claim 28, further combing the high purity spheniscidite with a lithium source to form lithium iron phosphate having a particle size in a range of 20-80 nm.