Preparation And In-situ Battery Reaction Of One-dimensional Copper Oxide Nanomaterials

With the steady growth of energy demand and consumption,the development of energy conversion and storage technologies has become especially important,which promote the researches of new ion battery anode materials.One-dimensional nano-metal oxides become the potential anode materials for the next-generation energy storage systems due to their high theoretical specific capacity,good cycle performance,high safety,and cheap availability etc.,thus they are also the best candidates for assembling in-situ nano-batteries.In this thesis,one-dimensional copper oxide nanomaterials are selected as electrode materials,including copper oxide nanowires?CuO NWs?and copper oxide nanotubes?CuO NTs?.In-situ transmission electron microscope technology is used to construct an open all-solid-state nanobattery,transmission electron microscopy?TEM?,electron diffraction patterns?EDPs?,high-resolution transmission electron microscopy?HRTEM?and electron energy loss spectroscopy?EELS?are used to study the real-time morphological,structural,and compositional changes of electrode materials during the lithiation/delithiation process.The energy storage mechanism of nanomaterials and the effects of their morphologies and structures are revealed,which provide the microscopic theoretical basis for the modification and design of nano-electrode materials.Twin CuO NWs are prepared by thermal oxidation method,Kirkendall holes in the oxide layer are observed.Meanwhile the mechanism of CuO NWs growth driven by the interdiffusion potential of copper ions and oxygen ions is proposed.In-situ Li-CuO NWs nano-battery is constructed in the environmental transmission electron microscope?ETEM?by using CuO NWs with twin structure as the cathode material,the lithiation/delithiation reaction mechanism and the relationship between lithiation kinetics and applied voltage are revealed.The twin boundaries are the rapid diffusion channels of Cu²⁺during thermal oxidation and Li⁺during lithiation.The irreversible phase transition of CuO?Cu?Cu₂O and the irreversible volume expansion are the main reasons for the capacity decay of the first cycle.Polycrystalline CuO NTs are prepared by combining hydrothermal method and thermal oxidation method,and the formation of the hollow structure can be regarded as the result of the growth of Kirkendall voids.Meanwhile the universality of kirkendall effect from micro to macro is revealed.In-situ Li-CuO NTs nano-battery is constructed in the ETEM by using polycrystalline CuO NTs as the cathode material,and the electrochemical lithiation/delithiation process of the nanotube is observed in-situ by means of applied voltage.The mechanism of the Li-CuO conversion reaction is revealed.CuO NTs undergo greater longitudinal expansion than NWs during the first cycle of lithium intercalation,resulting in a larger volume expansion rate,and the reaction is in accordance with the ion diffusion kinetic model.