Preparation And Electrochemical Properties Research For Nanostructured Nickie Oxide

In this thesis, we reviewed the recent reseach advances in the electrode materialsof lithium ion batteries and electrochemical capacitors, which are two types of themost important chemical energy storage devices. Nickel oxide (NiO), which is one ofthe most important family of functional inorganic materials, was chosen as theresearch object in the applications of these two devices due to its abundance, low cost,simple preparation and non-toxic.First, hydrothermal precesses with different conditions were employed tosynthetize NiO precursors with different crystal structures and morphologies, amongwhich the most electrochemical activity of NiO were obtained to be the electrocdematerials. Self-assembly ultrathin porous hierarchical NiO precursor andglobularflower-like hierarchical NiO precursor were successfully synthetized, whichcan be reasonably assigned to NiO2.45C0.74N0.25H2.90through the element analysis.Self-assembly ultrathin porous NiO nanosheets were obtained by further sinteringSelf-assembly ultrathin porous hierarchical NiO precursor in air. A unique NiO/GNShierarchical structure was prepared by electrostatic interaction between positivelycharged NiO nanosheets and negatively charged graphene oxide and then sintering inAr gas atmosphere. The ultrathin and porous structure was of benefit to fast Li+transfer and the large area of conducting graphene offers continuous and fastconducting pathways for electrons through the electrodes. Meanwhile, theself-aggregation of either NiO or graphene sheets can be impeded due to thesynergistic effect. The advantageous combination of ultrathin, porous and large area2D structure and conductive graphene endows the as-prepared hierarchical structure aexcellent performance of stable and high reversible discharge capacity up to1098mAh g-1even after50cycles at current density of100mA g-1, and good ratecapability of615mAh g-1at a high current density of4A g-1.Globularflower-like hierarchical NiO obtained by further sintering globularflower-like hierarchical NiO precursor in air would keep the ultrathin andporous structure, which could be an ideal electrode material of electrochemicalcapacitors. Rich porosity and large specific surface areas of this unique structureleaded to the feasibility that the electrolyte ions would contact with more electroactivesites efficiently. As a result, the porous hierarchical structured NiO not only exhibiteda high specific capacitance with435F g-1at20mV s-1and367at10A g-1but alsoshown a good capacitance retention property for1000cycles.