Structural characterization and electrochemical intercalation of Li in layered NaNiMnO obtained by freeze-drying method.

New data on the structure and reversible lithium intercalation properties of sodium-deficient nickel-manganese oxides are provided. Novel properties of oxides determine their potential for direct use as cathode materials in lithium-ion batteries. The studies are focused on NaNiMnO with x = 2/3. Between 500 and 700 °C, new layered oxides NaNiMnO with P3-type structure are obtained by a simple precursor method that consists in thermal decomposition of mixed sodium-nickel-manganese acetate salts obtained by freeze-drying. The structure, morphology, and oxidation state of nickel and manganese ions of NaNiMnO are determined by powder X-ray diffraction, SEM and TEM analysis, and X-ray photoelectron spectroscopy (XPS). The lithium intercalation in NaNiMnO is carried out in model two-electrode lithium cells of the type Li|LiPF(EC:DMC)|NaNiMnO. A new structural feature of NaNiMnO as compared with well-known O3-NaNiMnO and P2-NaNiMnO is the development of layer stacking ensuring prismatic site occupancy for Na ions with shared face on one side and shared edges on the other side with surrounding Ni/MnO octahedra. The reversible lithium intercalation in NaNiMnO is demonstrated and discussed. [ABSTRACT FROM AUTHOR]