Study On Synthesis And Structure And Properties Of Molybdenum Oxides

In this dissertation, several methods were developed to prepare the electrode materials for secondary lithium ion batteries. Layered compounds, including some metastable structure, had been successfully synthesized by the mild reactions and controllable process. Optical properties and electrochemical performances of thus-prepared compounds were investigated. The details are summarized as follows:1. Orthorhombic molybdenum trioxide (α-MoO₃) exhibits a unique layered structure, whose host lattice is suitable for Li⁺ insertion reaction. α-MoO₃ with unique flakelike morphology was synthesized by chemical precipitation and hydrothermal treatment at low temperature. The first discharge specific capacity ofα-MoO₃ reached 663 mA h g^-1 vs. Li metal at 0.1 mA cm^-2 (voltage range 1.2 - 3.5V), which is higher than that of α-MoO₃ prepared by solid-state method (360 mA h g^-1). Single crystalline α-MoO₃ nanobelts were synthesized by hydrothermal treatments. Excellent electrochemical performances were exhibited: the first discharge specific capacity is 961 mA h g^-1 at 0.1 mA cm^-2. Thus-prepared single crystalline α-MoO₃ nanobelts show potential to be the idea candidate materials of lithium ion battery.2. Metastable structures generally demonstrate new or enhanced properties compared to their thermodynamically stable forms. However, the synthesis of metastable compounds is often more difficult, which usually limits their properties research. Here, metastable hexagonal MoO₃ with high purity was successfully synthesized via a simple solution approach. It was realized by chemical precipitation, hydrothermal treatment and calcination. In the procedure of precipitation, the concentrated HCl plays a key role for the formation of the metastable h-MoO₃. XRD patterns and DTA profile of as-synthesized h-MoO₃ show that the metastable h-MoO₃...