Pre-swelled nanostructured electrode for lithium ion battery: TiO ₂-pillared layered MnO₂

Porous structure of layered manganate pillared with titania nanoparticles has been realized by the exfoliation and reassembling route. First, the layered protonic manganese oxide, H_0.13MnO₂·0.7H ₂O, is exfoliated by the intercalation of tetrabutylammonium (TBA) ions, and then the exfoliated manganate nanosheets are reassembled in the presence of titania nanoparticles, which results in porous nanohybrid materials. X-Ray diffraction (XRD), cross-sectional transmission electron microscopy (TEM), and Mn K-edge X-ray absorption spectroscopy (XAS) analyses clearly show that the titania nanoparticles with a diameter of 1 nm are successfully intercalated into the two dimensional manganate lattice without any deterioration of electronic structure and local symmetry of Mn ion. According to the N₂ adsorption-desorption isotherms, the present nanohybrid is determined to be highly porous with a high specific surface area (106 m ² g^-1), which is 10 times larger than that (11 m ² g^-1) of the pristine. Finally, electrochemical experiments demonstrate that the specific capacity of the present pillared material is 288 mA h g^-1, which is significantly larger than the theoretical value (193 mA h g^-1) from the physical mixture of the pristine potassium birnessite and titania nanoparticles.