Novel synthesis of layered LiNi1/2Mn1/2O2 as cathode material for lithium rechargeable cells

A new solution combustion synthesis of layered LiNi0.5Mn0.5O2 involving the reactions of LiNO3, Mn(NO3)2, NiNO3, and glycine as starting materials is reported. TG/DTA studies were performed on the gel-precursor and suggest the formation of the layered LiNi0.5Mn0.5O2 at low temperatures. The synthesized material was annealed at various temperatures, viz., 250, 400, 600, and 850 deg C, characterized by means of X-ray diffraction (XRD) and reveals the formation of single phase crystalline LiNi0.5Mn0.5O2 at 850 deg C. The morphology of the synthesized material has been investigated by means of scanning electron microscopy (SEM) and suggests the formation of sub-micron particles. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) studies on the synthesized LiNi0.5Mn0.5O2 powders indicate that the oxidation states of nickel and manganese are +2 and +4, respectively. Electrochemical galvanostatic charge-discharge cycling behavior of Li//LiNi0.5Mn0.5O2 cell using 1 M LiPF6 in EC/DMC as electrolyte exhibited stable capacities of ~125 mAh/g in the voltage ranges 2.8-4.3 V and 3.0-4.6 V and is comparable to literature reports using high temperature synthesis route. The capacity remains stable even after 20 cycles. The layered LiNi0.5Mn0.5O2 powders synthesized by this novel route have several advantages as compared to its conventional synthesis techniques.