Nitrates-melt synthesized LiNi0 8Co0 2O2 and its performance as cathode in Li-ion cells

Abstract

Layered LiNi0 8Co0 2O2 crystallizing in R-3̄m space group is synthesized by decomposing the constituent metal-nitrate precursors. Oxidizing nature of metal nitrates stabilizes nickel in +3 oxidation state, enabling a high degree of cation ordering in the layered LiNi0 8Co0 2O2. The powder sample characterized by XRD Rietveld refinement reveals < 2% Li-Ni site exchange in the layers. Scanning electron microscopic studies on the as-synthesized LiNi 0 8Co0 2O2 sample reflect well defined particles of cubic morphology with particle size ranging between 200 and 250 nm. Cyclic voltammograms suggest that LiNi0 8Co0 2O 2 undergoes phase transformation on first charge with resultant phase being completely reversible in subsequent cycles. The first-charge-cycle phase transition is further supported by impedance spectroscopy that shows substantial reduction in resistance during initial de-intercalation. Galvanostatic charge-discharge cycles reflect a firstdischarge capacity of 184 mAh g -1 which is stabilized at 170 mAh g-1 over 50 cycles. © Indian Academy of Sciences.