Hydrothermal synthesis of Na4Mn9O18 nanowires for sodium ion batteries

Abstract Na4Mn9O18 was recognized as the most interesting material for sodium ion batteries due to its low cost, high specific capacity and good cycle performance. The excellent electrochemical performance of Na4Mn9O18 nanostructures was shown in literature. In this work, Na4Mn9O18 nanowires were synthesized by hydrothermal reactions of Mn2O3 powder and NaOH solution at the temperatures of 185–205 °C for 48–96 h. The investigation of composition and structure of the synthesized products via scanning electron microscopy and X-ray diffraction analyses showed that major intermediate products at the low and high temperatures were Mn3O4 and birnessite Na0.55Mn2O41.5H2O, respectively. The synthesized Na4Mn9O18 nanowires showed a good electrochemical performance with discharge capacities of over 90 mAhg−1, and Coulombic efficiencies of more than 91% at a rate of 0.2C during 30 cycles of charge/discharge.