Micron-sized Na0.7MnO2.05 as cathode materials for aqueous rechargeable magnesium-ion batteries

Aqueous magnesium ion batteries have been identified as potential electrochemical energy storage system due to their similar electrochemical properties to lithium, safety, high abundance, and low cost. Here, micron-sized Na 0.7 MnO 2.05 is prepared by a facile sol-gel method used for cathode material in aqueous magnesium ion batteries. XRD, XPS, SEM, TEM, and EDS were used to test the composition, structure, and morphology of Na 0.7 MnO 2.05 . Na 0.7 MnO 2.05 material is electro-chemical active although the intercalation/deintercalation is much difficult for Mg 2+ . The reversible specific capacities of the Na 0.7 MnO 2.05 cathode material are estimated to be ca. 40, 35, 22, and 13 mAh·g −1 at the current density of 1 C, 2 C, 5 C, and 10 C, respectively. When the current density comes back to 1 C, the charge capacities recover to 40 mAh·g −1 . Furthermore, EIS and GITT measured show that the diffusion coefficient of Mg 2+ ion in lattice of Na 0.7 MnO 2.05 varies from 2.17 × 10 −11  cm 2 ·s −1 to 7.81 × 10 −11  cm 2 ·s −1 in charge process and changes from 6.34 × 10 −12  cm 2 ·s −1 to 7.14 × 10 −11  cm 2 ·s −1 in discharge process.