Cathodic material for sodium-ion rechargeable batteries based on NaxMnO2 were synthesized by glycine nitrate method and subsequent annealing at high temperatures. Different crystal structures with different morphologies were obtained depending on the annealing temperature: hexagonal layeredα-Na0.7MnO2.05 nanoplates were obtained at 850 °C, while 3-D tunnel structured Na0·4MnO2 and Na0·44MnO2, both with rod-like morphology, were obtained at 800 °C and 900 °C, respectively. The investigations of the electrochemical behavior of obtained cathodic materials in aqueous NaNO3 solution have shown that Na0·44MnO2 obtained at 900 °C has shown the best battery performance. Its initial discharge capacities are 123.5 mA h/g, 113.2 mA h/g, and 102.0 mA h/g at the high current densities of 1000, 2000 and 5000 mA/g, respectively.