Preparation method of anhydrous ferric pyrophosphate

The invention discloses a preparation method of anhydrous ferric pyrophosphate, wherein the method includes steps of adding 110-120 parts by weight of phosphoric acid in 300 parts by weight of de-ionized water and preparing to be phosphoric acid solution; controlling the solution temperature at 50-80 DEG C, and adding 56 parts by weight of 300 meshes-100 meshes of reduced iron powder under the stirring state and reacting for 3 hours, and then adding the acquired precursor liquid in a nanoscale sand grinding machine; performing ball milling for 2 hours and acquiring turbid liquid of which grain diameter distribution D5 is 200-400 nm; spraying and drying the acquired ball mill turbid liquid at 170 DEG C, and acquiring a spherical precursor powder body; at last, calcining the acquired spherical precursor powder body in the air at 600-800 DEG C for 8 hours, and then acquiring the anhydrous ferric pyrophosphate material. As the raw material for producing the lithium iron phosphate material, the calcining process i