Inorganic nanocrystalline and hybrid nanocrystalline particles (gamma-Fe2O3/PPY) and their contribution to electrode materials for lithium batteries

Nanoscale materials offer the advantage of combining structural effects (inside grain structure) with surface effects or grain-boundary effects. Therefore, the electrochemistry of this type of materials is very different from that of traditional microcrystalline ones mainly due to the contribution of the 'surface defects' allowing strong coulombic interactions between the inserted lithium ions and the surface ions called 'electrochemical grafting'. When electrochemical grafting is the first electrochemical step to take place, it can favor the power density and the cycling life of electrode materials. As illustrative examples, electrochemical behaviors of nanocrystalline oxides such as LiMn2O4, gamma-Fe2O3, and of nanohybrid inorganic-organic materials such as gamma-Fe2O3/PPY (PPY = polypyrrole) are presented. (C) 2004 The Electrochemical Society.