Method for preparing lithium iron phosphate nanopowder coated with carbon

Patent metadata

Field	Value
Publication number	US-10020499-B2
Application number	US-201414516779-A
Country	US
Kind code	B2
Filing date	Oct 17, 2014
Priority date	Jan 10, 2013
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

The present invention relates to a method for preparing a lithium iron phosphate nanopowder coated with carbon, including the steps of (a) preparing a mixture solution by adding a lithium precursor, an iron precursor and a phosphorus precursor in a glycerol solvent, (b) putting the mixture solution into a reactor and reacting to prepare amorphous lithium iron phosphate nanoseed particle, and (c) heat treating the lithium iron phosphate nanoseed particle thus to prepare the lithium iron phosphate nanopowder coated with carbon on a portion or a whole of a surface of a particle, and a lithium iron phosphate nanopowder coated with carbon prepared by the above method. The lithium iron phosphate nanopowder coated with carbon having controlled particle size and particle size distribution may be prepared in a short time by performing two simple steps.

First claim

What is claimed is:

1. A method for preparing a lithium iron phosphate nanopowder coated with carbon, comprising:
(a) preparing a non-aqueous mixture solution by adding a lithium precursor, an iron precursor and a phosphorus precursor in a nonaqueous glycerol solvent;
(b) putting the non-aqueous mixture solution into a reactor and reacting to prepare amorphous lithium iron phosphate nanoseed particle under pressure conditions of less than or equal to 10 bar; and
(c) heat treating and crystallizing the lithium iron phosphate nanoseed particle thus to prepare the lithium iron phosphate nanopowder coated with carbon on a portion or a whole of a surface of a particle,
wherein a particle diameter of an individual particle of the lithium iron phosphate nanopowder including the carbon coating layer is from 30 nm to 300 nm.

2. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 1 , wherein the nanoseed particle prepared in the above Step (b) go through at least one step among a cooling step, a washing step and a drying step.

3. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 1 , further comprising the step of adding an organic compound in the above Step (a), Step (b), or Step (c).

4. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 1 , wherein the above Step (b) is performed at a temperature less than or equal to a boiling point of the glycerol solvent.

5. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 1 , wherein the above Step (b) is performed at a temperature range of 120° C. to 290° C. for 0.1 to 24 hours.

6. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 1 , wherein the above Step (b) is performed at a temperature range of 150 to 290° C. for 0.1 to 5 hours.

7. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 1 , wherein the above Step (c) is performed at a temperature range of 400° C. to 900° C. for 0.5 to 5 hours.

8. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 2 , wherein the washing step is performed by consecutively using acetone and methanol.

9. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 2 , wherein the drying is performed at a temperature range of 20° C. to 160° C. for 2 to 40 hours.

10. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 1 , wherein the lithium precursor is at least one selected from the group consisting of lithium acetate dihydrate (CH 3 COOLi.2H 2 O), lithium hydroxide monohydrate (LiOH.H 2 O), lithium hydroxide (LiOH), lithium carbonate (Li 2 CO 3 ), lithium phosphate (Li 3 PO 4 ), lithium phosphate dodecahydrate (Li 3 PO 4 .12H 2 O), lithium oxalate (Li 2 C 2 O 4 ), and a mixture thereof.

11. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 1 , wherein the iron precursor is at least one selected from the group consisting of iron citrate (FeC 6 H 5 O 7 ), iron citrate hydrate (FeC 6 H 5 O 7 .nH 2 O), ferrous sulfate heptahydrate (FeSO 4 .7H 2 O), iron(II) oxalate dihydrate (FeC 2 O 4 .2H 2 O), iron acetyl acetonate (Fe(C 5 H 7 O 2 ) 3 ), iron phosphate dihydrate (FePO 4 .2H 2 O), ferric hydroxide (FeO(OH)), and a mixture thereof.

12. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 1 , wherein the phosphorus precursor is at least one selected from the group consisting of tri-ammonium phosphate trihydrate ((NH 4 ) 3 PO 4 .3H 2 O), ammonium phosphate ((NH 4 ) 2 HPO 4 ), ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ), phosphoric acid (H 3 PO 4 ), and a mixture thereof.

13. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 3 , wherein the organic compound is at least one selected from the group consisting of glucose, sucrose, galactose, fructose, lactose, starch, mannose, ribose, aldohexose, ketohexose, and a mixture thereof.

14. The method for preparing a lithium iron phosphate nanopowder coated with carbon of claim 3 , wherein the amount of the organic compound is 0.1 wt % to 5 wt % based on a total amount of the lithium iron phosphate nanoseed particle prepared in Step (b).

15. A lithium iron phosphate nanopowder coated with carbon comprising the lithium iron phosphate nanopowder coated with carbon prepared according to claim 1 and including particle having an olivine crystal structure,
wherein a carbon coating layer is formed on a portion or a whole of a surface of the particle and wherein a particle diameter of an individual particle of the lithium iron phosphate nanopowder including the carbon coating layer is from 30 nm to 300 nm.

16. The lithium iron phosphate nanopowder coated with carbon of claim 15 , wherein a thickness of the carbon coating layer is less than or equal to 10 nm.

17. A cathode active material comprising the lithium iron phosphate nanopowder coated with carbon according to claim 15 .

18. The cathode active material of claim 17 , further comprising at least one selected from a conductive agent, a binder and a filler.

19. A cathode for a lithium secondary battery comprising a cathode current collector, and the cathode active material of claim 17 coated on the cathode current collector.

20. A lithium secondary battery comprising the cathode of claim 19 , an anode, a separator and a non-aqueous electrolyte comprising a lithium salt.

Assignees

• Lg Chemical Ltd

Inventors

• Jun In Kook
• Cho Seung Beom
• Oh Myoung Hwan
• Jang Wook

Classifications

• H01M4/583

  Carbonaceous material, e.g. graphite-intercalation compounds or CFx · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• C01P2004/64

  Nanometer sized, i.e. from 1-100 nanometer · CPC title

• H01M4/0404

  by coating on electrode collectors · CPC title

• B82B3/0095 Primary

  Manufacture or treatments or nanostructures not provided for in groups B82B3/0009 - B82B3/009 · CPC title