Ferric phosphate and methods of preparation thereof

Abstract

High-purity crystalline ferric phosphate material with desirable characteristics for use in synthesis of nano-sized LFP cathode material are described. The ferric phosphate dihydrate material has as disclosed herein has a molar ratio of phosphorous to iron is from about 1.001 to about 1.05, a surface area of from about 25 m/g to about 65 m/g, and is substantially free of metallic or magnetic impurities. Methods of synthesizing high-purity crystalline ferric phosphate material with desirable characteristics for use in synthesis of nano-sized LFP cathode material are also described. In some embodiments, one or more magnetic traps are used during the reaction process and/or after the formation of the final product to remove magnetic impurities. In some embodiments, a synthetic method of ferric phosphate using multiple steps is described, wherein the intermediate of the synthesis is isolated and purified to improve the purity of the ferric phosphate material. In some embodiments, an iron compound is added to an aqueous solution of phosphoric acid. The solution pH and temperature are controlled to ensure the complete dissolution of the iron compound. The desired iron phosphate crystalline material can be obtained with high purity and high crystalline phase purity by controlling the pH and temperature of the solution.