Nanocrystalline Materials For Lithium Batteries

For a long time, only well crystalline materials have been considered as good electrodes for lithium-ion cells. Nanocrystalline materials are, however, being re-evaluated recently as ‘nanoscience’ advances. The electrochemistry of this kind of materials is much different from that of traditional crystalline ones because of their significant ‘surface effects’. The nanocrystalline materials are reported to have an enhanced electrochemical activity when the first electrochemical step is insertion of Li ions (discharge process). As illustrative examples, electrochemical behaviors of some nanocrystalline materials such as LiMn2O4, γ-Fe2O3, fluorine-doped tin oxide and potassium manganese oxyiodide, are presented and compared with their well-crystalline homologues. XRD, XPS, X-ray absorption and NMR spectroscopies were used as probe tools to differentiate the bulk (core) and local (surface) states. The “electrochemical grafting” concept will be given as a plausible explanation.