Preparation of LiFePO4/C composites by co-precipitation in the presence of stearic acid

Abstract

The olivine type compositions LiMPO4 (M = Fe, Mn, Co) are among the most attractive materials for the positive electrode of lithium-ion battery. The benefits of using LiFePO4 are excellent cycle life, high structural stability, low cost and environmental friendliness. Its main limitation is low total electrical conductivity, which can be overcome by carbon coating and/or the achievement of a small and homogeneous particle size distribution. Here is presented a simple and inexpensive route for obtaining LiFePO4/C composites by aqueous co-precipitation of an Fe(II) precursor material in the presence of stearic acid and subsequent heat treatment at different temperatures. Stearic acid serves as both chelating agent and carbonaceous material. During pyrolytic degradation stearic acid decomposes to carbon while creating reductive atmosphere. The crystal structures of the powders were revealed by X-ray powder diffraction. It was shown that phase purity of the synthesized powders is very dependent on calcination temperature, as well as their electrochemical properties.