Electrochemistry and spectroscopy of energy conversion and polynuclear aromatic materials.

摘要

The field of materials chemistry is becoming increasingly important in many technological disciplines, including batteries, fuel cells, hydrogen storage materials, and application of poly-nuclear aromatic compounds in solar cells, color copiers, sensors, and catalysis. This multidisciplinary research work focuses on the development, understanding, and characterization of novel materials for advanced lithium batteries and a unique series of polyaromatic compounds for application in solar cells and color copiers.; A general overview of materials and techniques used in this work is presented, including the electrochemistry, spectroscopy, thermal analysis, and x-ray diffraction. A unique electrochemical procedure based on carbon paste microelectrode was applied to study the electrochemistry of novel poly-nuclear aromatic compounds. X-ray diffraction and vibrational spectroscopy are also used to gain further information about their molecular organization in solid-state.; Conductivity of a novel electrolyte based on a multi-blend of organic carbonate solvents, has been studied over a wide range of temperatures (−40 to 70°C). An optimized electrolyte for an advanced lithium battery based on ternary solvent blend of linear and cyclic organic carbonates has been developed.; The nature of ion-association and ion-solvent interactions in complex electrolytes are studied using infrared spectroscopy. We have found a strong preferred solvation of lithium ion in electrolyte containing multi-blend solvent molecules.; The advanced lithium battery uses intercalation compounds with layered structure such as LiCoO₂ cathode, and lithiated graphite, (LiC ₆), anode. In this work, we have studied the reactivity of Li-C anode materials in contact with organic carbonate-based electrolyte, and have investigated the nature of the decomposition products formed on the electrode surface. A significant reactivity between the LiC₆ and organic electrolytes is observed, and is a major safety concern. A unique, yet simple procedure was developed for spectroscopy and X-ray diffraction of air sensitive materials.; The electrochemical properties of poly-aromatic molecules are studied using a novel carbon-paste micro-electrode technique. The electrochemical studies indicate that the charge transport in this class of compounds is diffusion controlled, and the radical anions that are formed during reduction of polyaromatics are stable enough to be observed during the oxidation to the neutral state.; IR spectra of polyaromatic molecules, in the far- and mid-IR have been obtained. Thermal analysis has shown that the PTCDA, and its derivatives used in this work, are thermally stable up to 400°C, and they are suitable for application in solar cells and color copiers.