Basic Medium Heterogeneous Solution Synthesis of α-MnO₂ Nanoflakes as an Anode or Cathode in Half Cell Configuration...

Nano α-MnO₂ is usually synthesized under hydrothermal conditions in acidic medium, which results in materials easily undergoing thermal reduction and offers single crystals often over 100 nm in size. In this study, α-MnO₂ built up of inter-grown ultra-small nanoflakes with 10 nm thickness was produced in a rapid two-step procedure starting via partial reduction in solution in basic medium subsequently followed by co-proportionation in thermal treatment. This approach offers phase-pure α-MnO₂ doped with potassium (cryptomelane type K_0.25Mn₈O₁₆ structure) demonstrating considerable chemical and thermal stability. The reaction pathways leading to this new morphology and structure have been discussed. The MnO₂ electrodes produced from obtained nanostructures were tested as electrodes of lithium ion batteries delivering initial discharge capacities of 968 mAh g^-1 for anode (0 to 2.0 V) and 317 mAh g^-1 for cathode (1.5 to 3.5 V) at 20 mA g^-1 current density. At constant current of 100 mA g^-1, stable cycling of anode achieving 660 mAh g^-1 and 145 mAh g^-1 for cathode after 200 cycles is recorded. Post diagnostic analysis of cycled electrodes confirmed the electrode materials stability and structural properties.