Novel synthesis of layered LiNi_1/2Mn_1/2O₂ as cathode material for lithium rechargeable cells

A new solution combustion synthesis of layered LiNi_0.5Mn _0.5O₂ 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 LiNi_0.5Mn_0.5O ₂ at low temperatures. The synthesized material was annealed at various temperatures, viz., 250, 400, 600, and 850°C, characterized by means of X-ray diffraction (XRD) and reveals the formation of single phase crystalline LiNi_0.5Mn_0.5O₂ at 850°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 LiNi_0.5Mn_0.5O₂ powders indicate that the oxidation states of nickel and manganese are +2 and +4, respectively. Electrochemical galvanostatic charge-discharge cycling behavior of Li//LiNi_0.5Mn_0.5O₂ cell using 1M LiPF₆ in EC/DMC as electrolyte exhibited stable capacities of ∼ 125mAh/g in the voltage ranges 2.8-4.3V and 3.0-4.6V and is comparable to literature reports using high temperature synthesis route. The capacity remains stable even after 20 cycles. The layered LiNi_0.5Mn _0.5O₂ powders synthesized by this novel route have several advantages as compared to its conventional synthesis techniques.