KCS

We have synthesized the 3D hierarchical assembly of spinel(LiMn₂O₄) nanoplates and layered 0D nanocrystalline (LiMnO₂) homologue through a low temperature hydrothermal treatment for nanostructured lithium manganese oxides in an aqueous basic medium. According to powder X-ray diffraction and electron microscopic analyses, the 3D spheres composed of spinel nanoplates could be prepared from the hydrothermal reaction between excess LiOH and layered δ-MnO₂ nanostructures whereas the hydrothermal alkali treatments for the 1D nanowires of α-MnO₂ led to the synthesis of the well-crystalline layered 0D nanocrystals. Mn K-edge X-ray absorption spectroscopy clearly demonstrated that tetravalent manganese ions are stabilized in the octahedral site of nanostructured layered lattice, whereas spinel nanoplate has lower average oxidation state of >+3.5. According to electrochemical measurements, the obtained nanostructured materials showed better electrode performance compared with bulk LiMn₂O₄ and bulk LiMnO₂. The present study clearly demonstrated that the phase transformation of the nanostructured α-MnO₂ and δ-MnO₂ precursors can provide useful routes to nanostructured lithium manganese oxides with various dimensionality and morphologies.