Electrochemical Li insertion into conductive polymer/V2O5 nanocomposites

Electrochemical insertion of Li into a series of ''nanocomposites'' comprised of alternating V2O5 sheets and conductive polymer layers [polypyrrole (PPY) and polyaniline (PANI)] was examined and compared to the pristine V2O5 material in terms of reversibility, Li site occupancy, and Li diffusion coefficients, and to the materials after oxidation treatment. The electrochemical characteristics are very sensitive to the nature of the polymer, its content, and location. The presence of surface polymer hinders Li insertion in these materials (by comparison to materials without surface polymer) and appears to result in the partial entrapment of Li ions. For modified [PANI](0.4)V2O5, polymer incorporation results in better reversibility and increased Li capacity in the nanocomposite. [PPY](0.40)V2O5 displays a greater first discharge capacity than the respective PANI material, but is not as cyclable as in O-2-[PANI](0.40)V2O5. O-2-treatment results in the reformation of a high-potential Li site that is lost during the reductive intercalative polymerization. Li chemical diffusion coefficients are greater for the O-2-[PANI]V2O5 nanocomposite than the xerogel by one order of magnitude, resulting in better performance at high current densities. Most important, the electrochemical response of these nanocomposites is greater than the sum of the two components (inorganic and organic), underlining the synergy of these hybrid materials.