Iron-tin oxides with CaFe2O4 structure as anodes for Li-ion batteries

To investigate the effect of matrix, counter ions and cycling conditions on the properties of mixed iron oxides, CaFe2O4, Li0.5Ca0.5 (Fe1.5Sn0.5)O-4 and NaFeSnO4 have been synthesized and their electrochemical performance studied. CaFe2O4 shows a reversible capacity of similar to200 mAh g(-1) at 60 mA g(-1) and 12-50 cycles in the range 0.005-3.0 V, but shows slight capacity fading when the upper voltage is reduced to 2.5 V. Li0.5Ca0.5(Fe1.5Sn0.5)O-4 gives a reversible capacity of similar to450 mAh g(-1) in the voltage range 0.005-3.0 V at a current density of 60 mA g(-1) over 5-30 cycles and shows slight capacity-fading up to 50 cycles. NaFeSnO4 displays drastic capacity-fading on cycling to 3.0 V, but has very good cycling performance (310-340 mAh g(-1) for to 4-110 cycles) on cycling between 0.005 and 1.0 V at 60 mA g(-1). The mechanism of operation of the electrodes, as well as the beneficial effects of the presence of Ca ions and cycling up to a 3.0 V cut-off in the Ca-ferrites, are discussed. (C) 2003 Elsevier B.V. All rights reserved.