NOVELTY - Synthesizing fine particle iron phosphate precursors (FP) and producing electrochemically active material lithium iron phosphate (LFP), comprises e.g.: (a) preparing a first solution comprising iron source compounds mixed in water and a second solution comprising phosphate source compound mixed in water; (b) adding the second solution to the first solution to form first mixture; (c) stirring the first mixture for 2-5 hours and adjust pH to 1-6.5 to form second mixture; and (d) heating second mixture at less than or equal to 25 degrees C to less than or equal to boiling point for 1-10 hours to obtain third mixture.    USE - The method is useful for synthesizing fine particle FP precursors and producing LFP, which is useful: in producing lithium secondary battery (all claimed); and as an ion storage device.    ADVANTAGE - The method: is efficient, cost effective, stable, scalable and provides LFP having good quality, increased power performance at very high discharge rate, enhanced electrochemical properties and excellent high-drain properties; and provides the lithium ion batteries having high voltage plateau retention at high charge and discharge rates, good discharge profile, high electronic conductivity and long cycle life.    DETAILED DESCRIPTION - Synthesizing fine particle iron phosphate precursors (FP) and producing electrochemically active material lithium iron phosphate (LFP), comprises: (a) preparing a first solution and a second solution, where the first solution comprises iron source compounds mixed in water, and the second solution comprises phosphate source compound mixed in water; (b) adding the second solution into the first solution with stirring in pre-determined molar ratios to form a first mixture; (c) stirring the first mixture for 2-5 hours and adjusting the pH to 1-6.5 to form a second mixture; (d) heating the second mixture at less than or equal to 25 degrees C to less than or equal to the boiling point for 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 at 60-105 degrees C for 2-12 hours to obtain the first fine particle iron phosphate hydrated precursor (FP1); (g) heating FP1 at 250-600 degrees C for 2-20 hours to generate second fine particle iron phosphate anhydrous precursor (FP2); (h) mixing pre-determined molar ratios of a lithium source compound and FP precursor (FP1 and/or FP2) in water and/or organic solvent in the presence of carbon source compound at a room temperature to less than or equal to the boiling point at atmospheric pressure for 2-8 hours to form the first lithium iron phosphate precursor (LFP1); (i) sintering the LFP1 in an inert atmosphere at 300-400 degrees C for 2-10 hours to form the second lithium iron phosphate precursor (LFP2); and (j) sintering the LFP1 and/or LFP2 in the inert atmosphere first at 300-400 degrees C for 2-5 hours, and then at 500-900 degrees C for 2-15 hours, to obtain a nanometer-sized electrochemically active material LFP. An INDEPENDENT CLAIM is also included for the nanometer sized LFP produced by the method.