Effects of zinc and manganese ions in aqueous electrolytes on structure and electrochemical performance of Na0.44MnO2 cathode material

The sodium manganese oxide, Na0.44MnO2, was synthesized by a solid-state reaction routine combined with a sol–gel process using Mn(CH3CO2)2·4H2O as the manganese source. Results show that the capacity and cycling stability of Na0.44MnO2 cathodes are enhanced significantly by using a hybrid aqueous electrolyte (Na2SO4, ZnSO4 and MnSO4). The energy storage mechanism of as-prepared Na0.44MnO2 in the hybrid aqueous electrolyte is associated with the insertion/extraction of zinc and sodium multi-ions with the help of synergistic effects between zinc and manganese ions and the quasi-reversible deposition–dissolution process of Mn2+ ions. The Na0.44MnO2 electrode displays both excellent storage properties with zinc, sodium and manganese ions (∼340 mA h g−1 at 100 mA g−1 after 150 cycles) and reversibility (∼100% coulombic efficiency during cycling). The excellent reversibility and good cycling properties indicate that the Na0.44MnO2 can be a promising material for energy storage devices by using a hybrid aqueous electrolyte.