Li-storage and cycling properties of spinel, CdFe_2O_4, as an anode for lithium ion batteries

摘要

Cadmium ferrite, CdFe_2O_4, is synthesized by urea combustion method followed by calcination at 900 deg 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, 0005-30 V vs Li at room temperature. CdFe_2O_4 shows a first cycle reversible capacity of 870 (+ - 10) mAhg~(-1) at 007C-rate, but the capacity degrades at 4 mAhg~(-1)per cycle and retains only 680 ((+ - 10) mAhg ' after 50 cycles. Heat-treated electrode of CdFe_2O_4 (300 deg 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 CdFe_2O_4(vs theoretical, 90 moles of Li) is maintained up to 60 cycles, with a coulombic efficiency, 96-98 percent . Rale capability of heat-treated CdFe_2O_4 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 approx 0.9 V, whereas the charge potential is approx 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.