Novel high volumetric energy density nanostructured electrode materials for biomedical applications.

摘要

A definitive focus is being made to develop cathode materials of higher energy and good power for primary and rechargeable lithium batteries upon the development of implantable biomedical devices (cardiac defibrillators). In this thesis, novel electroactive nanostructured silver metal oxyfluoride perovskites, Ag1+3Mo6+(O3F 3) and Ag1+3Nb5+(O2F 4) have been successfully synthesized by a mechanochemical reaction. The formation of these perovskites was investigated throughout the Ag-Mo / Nb composition range with the use of either Ag1+ or Ag 2+ in the form of AgF and AgF2 as the reactant, respectively. The compositional study combined with XRD and extensive Raman investigation was utilized to determine structure and cation distribution and infer oxidation state.;An electrochemical characterization of these silver metal oxyfluoride perovskite positive electrodes for Li batteries was investigated for the first time as a function of synthesis condition, stoichiometry and effect of Mo and Ag derived second phases. A detailed in-situ electrochemical study by XAS, Raman and XRD was performed, revealing a 3 electron silver displacement or conversion reaction at > 3 V and a 2 electron reduction of Mo6+ to Mo4+ in the region 3 V.;To further improve the rate capability of silver metal oxyfluorides, metallic Ag2F phase has been successfully synthesized through the mechanochemical reaction of Ag and AgF. Its unique metallic character within Ag layers lead to a very good electronic conductivity (7.89x10 -2 S/cm). The efficacy of SMOF composites consisting of conducting matrix (carbon black, Ag2F and Ag phase) for lithium battery was investigated through discharge rate studies. Results indicated that Ag 2F phase could be utilized as an alternative conductive additive with exceptional density.