| The increasing demand on renewable energy worldwide is driving the pursuit of cleaner, safer and higher-energy energy storage technologies, as the concerns about environmental pollution associated with the use of fossil fuels are becoming serious with the growth of population and economy. While solar and wind energies are intermittent, rechargeable batteries are so far the most viable option for electrical energy storage. Among the various battery systems such as lead-acid, nickel cadmium, nickel metal hydride, lithium based batteries have unmatchable combination of high energy and power density, which make them the desirable choice for electric vehicles, portable electronics and power tools. As the functionalities of the portable electronics become more sophisticated and the demand for electric vehicles and storage of electricity from renewable sources increases, other advanced battery technologies such as lithium sulfur batteries and magnesium ion batteries in addition to lithium ion batteries are being developed, where cost, energy, power, life and safety are all important parameters to be taken into accounted. In this doctorate dissertation work, electroactive materials for use in lithium ion batteries, lithium sulfur batteries, lithium primary batteries and magnesium ion batteries were investigated, and in-depth understanding of the electrochemical properties of these materials was gained.;Vanadium-based compounds are favorable materials for Li ion batteries due to the possibility of multiple electron transfers per formula unit within a desirable voltage range and thus a high energy density. Among the multiple oxide materials with vanadium redox centers, Li1+nV3O8 (n=0-0.2) is especially promising because of its superior electrochemical properties including high specific energy and good rate capability. Prior research efforts have centered on the modification of preparation approaches to improve the functional capacity of this material, as preparation conditions including annealing temperature have a strong impact on the electrochemical outcomes. Understanding phase transformation and structural change accompanying de(lithiation) is of great significance for achieving excellent cyclic stability of the electrode materials. From the view point of battery applications, the focus of this dissertation work on the Li1+nV3O8 material is on probing the phase evolution, phase distribution as well as impact of morphology and interfacial structure, which are vital for the practical implementation of this material. (Abstract shortened by ProQuest.). |
