Method for preparing lithium iron phosphate nanopowder

Patent metadata

Field	Value
Publication number	US-2015030918-A1
Application number	US-201414510370-A
Country	US
Kind code	A1
Filing date	Oct 9, 2014
Priority date	Jan 10, 2013
Publication date	Jan 29, 2015
Grant date	—

Abstract

The present invention relates to a method for preparing a lithium iron phosphate nanopowder, 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, and (b) putting the mixture solution into a reactor and heating to prepare the lithium iron phosphate nanopowder under pressure conditions of 1 bar to 10 bar, and a lithium iron phosphate nanopowder prepared by the method. When compared to a common hydrothermal synthesis method, a supercritical hydrothermal synthesis method and a glycothermal synthesis method, a reaction may be performed under a relatively lower pressure. Thus, a high temperature/high pressure reactor is not necessary and process safety and economic feasibility may be secured. In addition, a lithium iron phosphate nanopowder having uniform particle size and effectively controlled particle size distribution may be easily prepared.

First claim

What is claimed is:

1 . A method for preparing a lithium iron phosphate nanopowder, comprising the steps of:
(a) preparing a mixture solution by adding a lithium precursor, an iron precursor and a phosphorus precursor in a glycerol solvent; and (b) putting the mixture solution into a reactor and heating to prepare the lithium iron phosphate nanopowder under pressure conditions of 1 bar to 10 bar.

2 . The method for preparing a lithium iron phosphate nanopowder of claim 1 , further comprising the step of (c) heat treating the lithium iron phosphate nanopowder thus prepared to form a coating layer at a portion or a whole of a surface of an individual particle of the nanopowder.

3 . The method for preparing a lithium iron phosphate nanopowder of claim 1 , wherein the lithium iron phosphate nanopowder prepared in Step (b) is sequentially conducted a washing step and a dring step.

4 . The method for preparing a lithium iron phosphate nanopowder of claim 1 , wherein 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 of claim 1 , wherein Step (b) is performed at a temperature range of 150° C. to 290° C.

6 . The method for preparing a lithium iron phosphate nanopowder of claim 1 , wherein Step (b) is performed for 1 to 72 hours.

7 . The method for preparing a lithium iron phosphate nanopowder 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.

8 . The method for preparing a lithium iron phosphate nanopowder 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.

9 . The method for preparing a lithium iron phosphate nanopowder 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.

10 . The method for preparing a lithium iron phosphate nanopowder of claim 2 , wherein the heat treating is performed by heating to a temperature range of 400° C. to 900° C.

11 . The method for preparing a lithium iron phosphate nanopowder of claim 3 , wherein the washing step is performed by sequentially using acetone and methanol.

12 . A lithium iron phosphate nanopowder comprising the lithium iron phosphate nanopowder prepared according to claim 1 and having an olivine crystal structure.

13 . The lithium iron phosphate nanopowder of claim 12 , wherein a particle diameter of the lithium iron phosphate nanopowder is from 30 nm to 300 nm.

14 . The lithium iron phosphate nanopowder of claim 12 , wherein a particle size distribution of the lithium iron phosphate nanopowder is less than or equal to 50% of an average value of the particle diameter.

15 . The lithium iron phosphate nanopowder of claim 12 , further comprising a carbon coating layer or a glassy lithium compound coating layer on a surface of a particle of the lithium iron phosphate nanopowder.

16 . The lithium iron phosphate nanopowder 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 according to claim 12 .

18 . The cathode active material of claim 17 , further comprising a conductive agent, a binder and a filler.

19 . A cathode for a lithium secondary battery comprising the cathode active material of claim 17 .

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

Classifications

• Y10T428/2982

  Particulate matter [e.g., sphere, flake, etc.] · CPC title

• C01P2004/03

  obtained by SEM · CPC title

• H01M4/366

  as layered products · CPC title

• H01M4/625

  Carbon or graphite · CPC title

• C01P2004/64

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