PROCESS FOR THE PREPARATION OF MICROCRYSTALLINE LIFEPO4, WHICH IS SPECIFICALLY SUITABLE AS CATHODE MATERIAL IN LITHIUM BATTERIES

摘要

This patent concerns a process for producing microcrystalline lithium iron phosphate (LiFePO 4 ) which is specifically suitable as cathode material in lithium batteries. Such process is characterized by the reduction of iron (III) phosphate (FePO 4 ) and its lithiation, as well as the crystallization of the product thus obtained through a single in airheat treatment. The product of such reaction is nano-sized lithium iron phosphate that is suitable to be used as cathode material in high-performance lithium batteries. The initial iron (III) phosphate (FePO 4 ) is obtained, in the presence of phosphate ions (HPO 4 2- ), through the oxidation of ferrous sulfate (FeSO 4 ) in an aqueous solution as a result of the use of hydrogen peroxide, thus causing the precipitation of iron (III) phosphate. Iron (III) phosphate can also be obtained through the direct precipitation of iron sulfate (Fe 2 (SO 4 ) 3 ) in the presence of phosphate ions(HPO 4 2- ). The aforementioned heat treatment is necessary for the elimination of the water of crystallization, as well as the subsequent transformation of the material through the reduction, lithiation and crystallization thereof, which is carried out in a single step by mixing iron (III) phosphate with a suitable lithiating and reducing agent (lithium acetate) and maintaining the mixture at a temperature ranging between 550°C and 650°C for a period of not less than 15 minutes.