Hexagonal-layered Na_0.7MnO_2.05 via solvothermal synthesis as an electrode material for aqueous Na-ion supercapacitors

The layered sodium manganese oxides Na_0.7MnO_2.05 material was synthesized using Na₂CO₃ and Mn₃O₄ precursors via a solvothermal method at different temperatures. The X-ray diffraction (XRD) shows that the Na_0.7MnO_2.05 sample has a high crystallinity with hexagonal crystal system. The electrochemical performance was characterized by cyclic voltammetry (CV), impedance measurements and galvanostatic charge–discharge tests in symmetric Na-ion supercapacitors with 1 mol L⁻¹ Na₂SO₄ solution as electrolyte. The Na_0.7MnO_2.05 material shows a high specific capacity of about 162.5 F g⁻¹ at a current density of 50 mA g⁻¹ and a high coulombic efficiency approaching 100%. Even at a current density of 200 mA g⁻¹, the discharge capacity of the material can reach to 146 F g⁻¹. This electrode material holds great promise for practical applications. - Highlights: • Novel electrode material for supercapacitor: hexagonal-layered Na_0.7MnO_2.05. • Na_0.7MnO_2.05 is synthesized using Mn₃O₄ precursors via solvothermal method. • Obtained Na_0.7MnO_2.05 exhibits superior electrochemical performance.