Li-storage and cycling properties of spinel, CdFe2O4, as an anode for lithium ion batteries

Cadmium ferrite, CdFe2O4, is Synthesized by urea combustion method followed by calcination at 900 degrees C and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) techniques. The Li-storage and cycling behaviour are examined by galvanostatic cycling, cyclic voltammetry (CV) and impedance spectroscopy in the voltage range, 0.005-3.0 V vs Li at room temperature. CdFe2O4 shows a first cycle reversible capacity of 870 (+/- 10) mAhg(-1) at 0.07C-rate, but the capacity degrades at 4 mAhg(-1) per cycle and retains only 680 (+/- 10) mAhg(-1) after 50 cycles. Heat-treated electrode of CdFe2O4 (300 degrees C; 12 h, Ar) shows a significantly improved cycling performance under the above cycling conditions and a stable capacity of 810 (+/- 10) mAhg(-1) corresponding to 8.7 moles of Li per mole of CdFe2O4 (vs theoretical, 9.0 moles of Li) is maintained up to 60 cycles, with a coulombic efficiency, 96-98%. Rate capability of heat-treated CdFe2O4 is also good: reversible capacities of 650 (+/- 10) and 450 (+/- 10) mAhg(-1) at 0.5 C and 1.4 C (1 C = 840 mAg(-1)) are observed, respectively. The reasons for the improved cycling performance are discussed. From the CV data in 2-15 cycles, the average discharge potential is measured to be similar to 0.9 V, whereas the charge potential is similar to 2.1 V. Based on the galvanostatic and CV data, ex situ-XRD, -TEM and -SAED studies, a reaction mechanism is proposed. The impedance parameters as a function of voltage during the 1st cycle have been evaluated and interpreted.