A solution-precursor synthesis of carbon-coated LiFePO4 for Li-ion cells

Carbon-coated, olivine-phase LiFePO4 suitable for lithium-ion batteries have been prepared via a novel, one-step, low-cost synthesis route from aqueous precursor solutions of Fe(NO3)(3), LiCH3COO, H3PO4, and sucrose. Sucrose additions up to a mole fraction of 25% were found to suppress crystallization of the salts during the first stages of pyrolysis, thereby reducing elemental segregation and facilitating the formation of the olivine structure below 500 degrees C in a single heating step. Sucrose also acted as a reducing agent and a source of carbon to form a conductive network in the active material during synthesis, leading to a higher capacity than materials in which sucrose was substituted with acetylene black. After additional treatment with sucrose at 700 degrees C, the material achieved a capacity of 162 mAh g(-1) at the C/14 rate and 158 mAh g(-1) at C/3.5 in the voltage range 2.0/4.5 V vs Li. (c) 2005 The Electrochemical Society.