Iron-based composite oxides as alternative negative electrodes for lithium-ion batteries

Nanosized lithiated iron oxides with 10 and 50 wt.% SiO2 were prepared by a sol–gel method using 1 M Fe(NO3)3 9H2O and 1 M LiNO3 aqueous solutions in a stoichiometric ratio of 1:1 and colloidal silica. Dried xerogel was calcinated at 700 C for 4 h in air. The X-ray data of samples synthesized using 10% and 50% SiO2 showed the presence of a mixture of two phases: a-LiFeO2 and Li1–xFe5O8 (0 < x £ 0.1) for a sample containing 10% SiO2 and LiFe(SiO3)2 and Fe2O3 (h) for a sample with 50% SiO2. The electrochemical behaviour of the compounds was investigated galvanostatically within the 0.01–3.0 V range at a current density of 0.80 mA cm–2. The Li/LixFeyOz (10%) SiO2 cell showed a high initial reversible capacity of 1,080 mA h g–1 and a capacity of 600 mA h g–1 at the 30th cycle. Accounting these results is the presence of a SiO2 phase which stabilizes the structure of the active mass on cycling.The mean charge voltage (1.8 V) and the discharge voltage of 1.0 V versus Li+ reference electrode as well as the high reversible capacity indicate that this material is suitable for use as anode in lithium-ion batteries.