EVOLUTION OF MICROSTRUCTURE AND PHASE COMPOSITION UPON ANNEALING OF <font>LiFePO</font>₄ PREPARED BY A LOW TEMPERATURE METHOD

Abstract

The effect of annealing of nanosized LiFePO 4 powder on microstructure, phase composition, iron valence state and electrical conductivity has been studied. Careful microstructural characterization of the as-prepared powder using high resolution TEM revealed presence of {010}-type crystal planes at the surface of crystallites, which seem to be beneficial to electrochemical activity. The second part of the work is focused on explanation of presence and evolution of Fe 3+ detected in the material. Transmission and CEMS modes of Mössbauer spectroscopy together with TEM allowed for ruling out concept of amorphous layers containing Fe 3+ ions covering crystalline LiFePO 4 grains.