LIFePO4 FLAKES FOR LI-ION BATTERY AND METHOD FOR MANUFACTURING THE SAME

Abstract

LiFePO 4 flakes for a Li-ion battery and a method for manufacturing the same are disclosed. The LiFePO 4 flakes of the present invention have a thickness of 5 nm-200 nm, and the angle between the flat surface normal of the flake and the Li-ion diffusion channel is 0°-80°. In addition, according to the present invention, the LiFePO 4 flakes with short Li ion diffusion path can be prepared through a simple process. Hence, not only the charge-discharge efficiency of the Li-ion battery can be improved by use of the LiFePO 4 flakes of the present invention, but also the cost of the Li-ion battery can be further reduced.

What is claimed is: 
     
         1 . A method for manufacturing LiFePO 4  flakes for a Li-ion battery, comprising the following steps:
 (A) providing a mixed organic solution by reflux, which comprises Li, Fe, and P, wherein the Li contained in the mixed organic solution is derived from a Li-containing precursor or a P and Li-containing precursor, the Fe contained in the mixed organic solution is derived from an Fe-containing precursor or a P and Fe-containing precursor, and the P contained in the mixed solution is derived from a P-containing precursor, a P and Li-containing precursor, or a P and Fe-containing precursor;   (B) heating the organic mixed solution to obtain preliminary products; and   (C) heat-treating the preliminary products to obtain LiFePO 4  flakes.   
     
     
         2 . The method as claimed in  claim 1 , wherein the organic mixed solution is heated under an atmosphere or with an introduced gas flow to obtain the preliminary products, in step (B). 
     
     
         3 . The method as claimed in  claim 1 , wherein the preliminary products are heat-treated under an atmosphere or with an introduced gas flow to obtain the LiFePO 4  flakes, in step (C). 
     
     
         4 . The method as claimed in  claim 1 , wherein the Li-containing precursor is at least one selected from the group consisting of LiOH, Li 2 CO 3 , LiNO 3 , CH 3 COOLi, Li 2 C 2 O 4 , Li 2 SO 4 , LiCl, LiBr, and LiI. 
     
     
         5 . The method as claimed in  claim 1 , wherein the Fe-containing precursor is at least one selected from the group consisting of FeCl 2 , FeBr 2 , FeI 2 , FeSO 4 , (NH 4 ) 2 Fe(SO 4 ) 2 , Fe(NO 3 ) 2 , FeC 2 O 4 , (CH 3 COO) 2 Fe, and FeCO 3 . 
     
     
         6 . The method as claimed in  claim 1 , wherein the P-containing precursor is at least one selected from the group consisting of H 3 PO 4 , NaH 2 PO 4 , Na 2 HPO 4 , Mg 3 (PO 4 ) 2 , and NH 4 H 2 PO 4 . 
     
     
         7 . The method as claimed in  claim 1 , wherein the P and Li-containing precursor is at least one selected from the group consisting of LiH 2 PO 4 , Li 2 HPO 4 , and Li 3 PO 4 . 
     
     
         8 . The method as claimed in  claim 1 , wherein the P and Fe-containing precursor is at least one selected from the group consisting of Fe 3 (PO 4 ) 2 , and FePO 4 . 
     
     
         9 . The method as claimed in  claim 1 , wherein the mixed organic solution further comprises: at least one selected from the group consisting of a surfactant, a polymer electrolyte, and a stabilizer. 
     
     
         10 . The method as claimed in  claim 1 , wherein an organic solvent in the mixed organic solution is at least one selected from the group consisting of ethylene glycol (EG), diethylene glycol (DEG), glycerol, triethylene glycol (TEG), tetraethylene glycol (TTEG), polyethylene glycol (PEG), Dimethyl sulfoxide (DMSO), and N,N-dimethylmethanamide (DMF). 
     
     
         11 . The method as claimed in  claim 2 , wherein the atmosphere or the introduced gas flow comprises one selected from the group consisting of N 2 , He, Ne, Ar, Kr, Xe, CO, methane, N 2 —H 2  mixed gas, and a mixture thereof. 
     
     
         12 . The method as claimed in  claim 3 , wherein the atmosphere or the introduced gas flow comprises one selected from the group consisting of N 2 , He, Ne, Ar, Kr, Xe, CO, methane, N 2 —H 2  mixed gas, and a mixture thereof. 
     
     
         13 . The method as claimed in  claim 9 , wherein the surfactant is Cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), or Triton-X100. 
     
     
         14 . The method as claimed in  claim 9 , wherein the polymer electrolyte is polyvinylpyrollidone (PVP), peroxyacetic acid (PAA), Polyethyleneimine (PEI), or polyacrylamide (PAM). 
     
     
         15 . The method as claimed in  claim 9 , wherein the stabilizer is Polyvinyl Alcohol (PVA), or polyvinyl acetate (PVAc). 
     
     
         16 . The method as claimed in  claim 1 , wherein the organic mixed solution is heated to and reacted at 105°-350° C., in step (B). 
     
     
         17 . The method as claimed in  claim 1 , wherein the organic mixed solution is reacted for 10 hrs-20 hrs. 
     
     
         18 . The method as claimed in  claim 1 , wherein the preliminary products are heat-treated at 300°-700° C., in step (C). 
     
     
         19 . The method as claimed in  claim 1 , wherein the preliminary products are heat-treated for 1 hr-20 hrs. 
     
     
         20 . The method as claimed in  claim 1 , wherein the LiFePO 4  flakes have a thickness of 5 nm-200 nm, and an angle between a flat surface normal of the LiFePO 4  flakes and a Li-ion diffusion channel is 0°-80°. 
     
     
         21 . The method as claimed in  claim 1 , wherein the LiFePO 4  flakes have olivine structures.