Reversible and rapid discharge-charge performance of gamma-Fe2O3 prepared by aqueous solution method as the cathode for lithium-ion battery

A composite of gamma-Fe2O3 and acetylene black (AB) was fabricated by the thermal treatment of a composite of gamma-FeOOH and AB synthesized by an aqueous solution method. In the composite, acicular gamma-Fe2O3 particles (20 x 200 nm) were observed by transmission electron microscopy, while crystallites of gamma-Fe2O3 were estimated to be several nanometers in size by X-ray diffraction. The composite of gamma-Fe2O3 and AB was examined as the cathode for lithium ion battery in the range of 4.3 V and 1.5 V (vs Li/Li+) and could be discharged and charged rapidly at a current density of 1 A g(-1)- Fe2O3. After an unidentified initial side reaction was completed, high coulomb efficiency and capacity retention was found. The ratio of the discharge capacity at the 50th cycle to that at the sixth was ca. 97%. The reversible intercalation capacity was estimated to be x = 0.52, in terms of LixFe(2)O(3), and then no irreversible structural change of iron and oxide ions to the rock- salt arrangement occurred. Nonetheless, the iron and oxide ions in the spinel structure changed to the rock-salt arrangement, when the composite was held at 1.5 V for a long period, > 400 h, or discharged below 1.3 V. (c) 2007 The Electrochemical Society.