Patent ID: 9139429
Filing Date: 2015-09-22
Classification: B82Y,C01B,H01M,Y02E

Abstract:
1. A method for synthesizing fine particle iron phosphate precursors (FP) and their application in producing electrochemically active material lithium iron phosphate (LFP), comprising the steps of: (a) preparing a first solution and a second solution, wherein the first solution comprises an iron source compound mixed in water, and wherein the second solution comprises a phosphate source compound mixed in water; (b) adding the second solution into the first solution with stirring in a pre-determined molar ratio to form a first mixture, wherein the pre-determined molar ratio is a molar ratio of ferric or ferrous to phosphate in the first mixture; (c) stirring the first mixture for about 2-5 hours and adjusting pH in a range of about 1-6 to form a second mixture; (d) heating the second mixture at a first temperature in a range of about 25-100° C. for about 1-10 hours to obtain a third mixture; (e) separating solid substance from the third mixture and rinsing it with water to obtain a solid substance; (f) drying the solid substance by heating it at a second temperature in a range of about 60-105° C. for about 2-12 hours to obtain a first fine particle iron phosphate hydrated precursor (FP1), wherein the FP1 has a tap density in a range of about 0.5-3 g/cm (g) heating the FP1 at a third temperature in a range of about 250-600° C. for about 2-20 hours to generate a second fine particle iron phosphate anhydrous precursor (FP2), wherein the FP2 has a tap density in a range of about 0.5-3 g/cm (h) mixing a lithium compound and at least one of the FP1 and the FP2 at a molar ratio in water and/or an organic solvent in the presence of a carbon source compound, at a temperature between about room temperature to less than or equal to 40° C. at atmospheric pressure for about 2-8 hours to form a first lithium iron phosphate precursor (LFP (i) sintering the LFP1 in an inert atmosphere at a temperature between about 300° C. to about 500° C. for about 2-10 hours to form a second lithium iron phosphate precursor (LFP2); and (j) sintering the LFP1 or the LFP2 or a mixture thereof in an inert atmosphere first at a temperature between about 300° C. to about 400° C. for about 2-5 hours and then at a temperature between about 500° C. to about 900° C. for about 2-15 hours, thereby obtaining a nanometer-sized electrochemically active material LFP.