Lithium metal phosphates, method for producing the same and use thereof as electrode material

• US 20070054187A1
• Filed: 11/14/2004
• Published: 03/08/2007
• Est. Priority Date: 11/14/2003
• Status: Active Grant

• Current Assignee: Johnson Matthey PLC
• Original Assignee: Sud-Chemie AG (Clariant AG)
• Inventors: Nuspl, Gerhard, Wimmer, Lucia, Eisgruber, Max
• Granted Patent: US 7,807,121 B2
• Time in Patent Office: Days
• US Class Current: 429/218.100
• CPC Class Codes: C01B 25/45 containing plural metal, or metal and ammonium
• 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 2004/021 Physical characteristics, e.g. porosity, surface area
• CPC Class Codes: H01M 4/5825 Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
• CPC Class Codes: H01M 4/625 Carbon or graphite
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]

Abstract

The invention describes a process for producing a compound of the formula LiMPO₄, in which M represents at least one metal from the first transition series, comprising the following steps: a) production of a precursor mixture, containing at least one Li⁺ source, at least one M²⁺ source and at least one PO₄³⁻ source, in order to form a precipitate and thereby to produce a precursor suspension; b) dispersing or milling treatment of the precursor mixture and/or the precursor suspension until the D90 value of the particles in the precursor suspension is less than 50 μm; and c) the obtaining of LiMPO₄ from the precursor suspension obtained in accordance with b), preferably by reaction under hydrothermal conditions. The material obtainable by this process has particularly advantageous particle size distributions and electrochemical properties when used in electrodes.

Claims

1. Process for producing a compound of the formula LiMPO₄, comprising:

a. producing a precursor mixture containing at least one Li⁺ source, at least one M²⁺ source and at least one PO₄³⁻

source, wherein M comprises at least one metal from the first transition series;

in order to form a precipitate and thereby to produce a precursor suspension;

b. dispersing or milling the precursor mixture or suspension until the D90 value of particles in a precipitate of the precursor mixture or suspension are less than 50 μ

m; and

c. obtaining LiMPO₄ from the precursor mixture or suspension by reaction under hydrothermal conditions.

2. Process according to claim 1, characterized in that the D90 value of the particles is at most 25 μ

m.

3. Process according to claim 1, characterized in that M comprises Fe.

4. Process according to claim 1, characterized in that M is selected from Fe, Mn, Co and Ni and mixtures thereof.

5. Process according to claim 1, characterized in that the LiMPO₄ is in pure-phase form.

6. Process according to claim 1, characterized in that the dispersing or milling begins before or during precipitation of the particles in the precursor mixture or suspension and is continued until the precipitation has concluded.

8. Process according to claim 1, characterized in that evaporation does not occur prior to the reaction of the precursor mixture or suspension under hydrothermal conditions.

9. Process according to claim 1, characterized in that sintering does not take place prior to the reaction of the precursor mixture or suspension under hydrothermal conditions.

10. Process according to claim 1, characterized in that the LiMPO₄ is dried following the reaction under hydrothermal conditions.

11. Process according to claim 1, characterized in that the production of the precursor mixture or suspension or the reaction under hydrothermal conditions takes place in the presence of at least one further component selected from a carbon-containing substance, an electron-conducting substance, the precursor of the electron-conducting substance, and mixtures thereof.

12. Process according to claim 11, characterized in that the electron-conducting substance is selected from conductive carbon, carbon fibers and mixtures thereof.

13. Process according to claim 11, characterized in that the precursor of the electron-conducting substance comprises a sugar compound.

14. Process according to claim 1, characterized in that the Li⁺ source is selected from LiOH, Li₂CO₃ and mixtures thereof.

15. Process according to claim 1, characterized in that the Fe²⁺ source is selected from FeSO₄, FeCl₂, FeNO₃, Fe₃(PO₄)₂, an organyl salt of iron and mixtures thereof.

16. Process according to claim 1, characterized in that the PO₄³⁻

source is selected from phosphoric acid, a metal phosphate, hydrogen phosphate, dihydrogen phosphate and mixtures thereof.

17. Process according to claim 1 characterized in that water is a solvent for the precursor mixture or suspension.

18. Process according to claim 1, characterized in that the Li⁺ source and the M²⁺ source are in the form of aqueous solutions, and the PO₄³⁻

source is in the form of a liquid or an aqueous solution.

19. Process according to claim 1, characterized in that the precipitate formed comprises at least one precursor of LiMPO₄.

20. Process according to claim 1, characterized in that the hydrothermal conditions comprise a temperatures between 100 and 250°

C., and a pressure from 1 bar to 40 bar.

21. Process according to claim 1, characterized in that the components of the precursor mixture or suspension are present in a stoichiometric ratio selected from:

a. 1 mole Fe²⁺;

1 mole PO₄³⁻

;

1 mole Li*,

b. 1 mole Fe²⁺;

1 mole PO₄³⁻

;

3 mole Li*, and

c. any mixing ratio between a. and b.

22. Process according to claim 1, characterized in that the reaction under hydrothermal conditions takes place under an inert gas atmosphere.

23. Process according to claim 1, characterized in that the M²⁺ source and the PO₄³⁻

source are first mixed in an aqueous solvent under an inert gas atmosphere, followed by the addition of the Li⁺ source under a protective gas or inert atmosphere, and then the reaction under hydrothermal conditions is carried out.

24. Process according to claim 1, characterized in that the dispersing or milling comprises a treatment with a dispersing means selected from Ultraturrax stirrers, mills, such as colloid mills or Manton-Gaulin mills, intensive mixers, centrifugal pumps, in-line mixtures, mixing nozzles, such as injector nozzles, ultrasound appliances and combinations thereof.

25. Process according to claim 1, characterized in that a stirring mechanism is used for the dispersing or milling conducted along with the introduction of power, calculated according to the formula P=2 π

n M, where M represents the torque and n represents the rotational speed, being at least 5 kW/m³.

26. Process according to claim 11, characterized in that the further component is used as a crystallization nucleus in the precursor mixture or solution.

28. The process of claim 1, wherein the LiMPO₄ has a mean particle size, D50 value of less than 0.8 μ

m.

29. The process of claim 1, wherein the D10 value of the particles is less than 0.4 μ

m and the D90 value is less than 3.0 μ

m.

30. The process of claim 29, wherein the difference between the D90 value and the D10 value of the particles is no more than 2 μ

m.

31. The process of claim 1, wherein the BET surface area of the particles is more than 3.5 m²/g.

36. Process according to claim 1, characterized in that the LiMPO₄, after the hydrothermal treatment is separated off by filtration or centrifuging, is dried and deagglomerated.

37. Process according to claim 1, characterized in that the LiMPO₄, obtained from the hydrothermal treatment is mixed with at least one carbon precursor material, such as sugar or cellulose, by kneading.

38. Process according to claim 37, characterized in that the mixed material produced is dried and heated to a temperature between 500°

C. and 1000°

C., during which operation the carbon precursor material is pyrolyzed to form carbon.

39. Process according to claim 38, characterized in that the pyrolysis process is followed by a milling or deagglomeration treatment.

40. Process according to claim 38, characterized in that the drying is carried out under a protective gas, in air or in vacuo at temperatures of from 50°

C. to 200°

C., and the pyrolysis is carried out under a protective gas.

41. LiMPO₄ particles produced by the process of claim 1, wherein said particles have a particle size distribution such that the D90 value for said particle aggregates is less than 3.0 μ

m.

42. The LiMPO₄ particles of claim 41, wherein the D90 value of said particles is less than 2.0 μ

m.

43. LiMPO₄ particles produced by the process of claim 1, wherein the difference between the D90 value of the particles and the D10 value is no more than 2 μ

m.

44. LiMPO₄ particles of claim 43, wherein the difference between the D90 and the D10 value is less than 1.5 μ

m.

7. (canceled)

27. (canceled)

32. (canceled)

33. (canceled)

34. (canceled)

35. (canceled)