Engineering And Fabrication Of Nanostructured Metal Oxide Anodes For High Performance Lithium Ion Batteries

Lithium-ion batteries (LIBs) are considered as the most promising power sources because of their high energy density, high working voltage, long cycle life, stable discharge voltage, low self-discharge rates, no memory effect and environmental friendliness. The commercialized graphite-based anode materials exhibit excellent capacity retention performance, but the low theoretical specific capacity (372mA h g-1) and worse rate capability, which limit the application for high energy density and power density batteries. Therefore, it is essential to develop new anode materials with higher specific capacity to replace graphite. Transition metal oxides have been considered as promising alternative anode materials for LIB applications owing to their high theoretical capacities.In this thesis, we designed and fabricated a series of self-supported nanostructured NiO electrodes for high performance LIBs by combining the advantage of nanomaterials and thin film. The electrodes exhibit not only high specific capacities and excellent rate capability, but also the improved areal capacities. Based on the results of the NiO system, we extend the research object to the Co3O4anode.The main contents and results are listed below:1. A simple thermal oxidation approach has been used to fabricate nanostructured NiO electrodes. Galvanostatic battery testing showed that the NiO electrode exhibits excellent rate capability and cycle performance. It can deliver a reversible capacity up to783mA h g-1(the corresponding areal capacity is0.39mA h cm-2) after50cycles at a rate of0.2C, and a capacity higher than375mA h g-1at a rate as high as20C. Moreover, porous NiO electrodes with different pore sizes are obtained at various oxidation conditions. The effects of the nanopore sizes and mass loading on the electrochemical properties of the prepared NiO electrodes have been systematic investigated.2. NiO nanocone array (NCA) electrode with high capacity, good cycling stability and excellent rate capability was fabricated by combining electrodeposition with thermal oxidation method. It was shown that the electrode can deliver a reversible capacity up to1058mA h g-1(the corresponding areal capacity is0.85mA h cm-2) after100cycles at a rate of0.2C, and a capacity higher than436mA h g-1at a rate as high as10C. It is important to note that when compared with the nanostrucrured NiO electrode obtained from pure Ni foam, the mass loading, specific and areal capacity of the NiO NCA have been improved with60%,17%and90%, respectively. Moreover, the morphology and structure of the NiO NCA after cycling have also been researched.3. Mesoporous NiO nanosheet networks (NSNs) with a thickness of～5.3μm were fabricated on Ni foam by a simple solvothermal method combined with subsequent calcinations. Benefiting from the favorable macro/meso-porous structures as well as the great loading of the synthesized NiO, the NSNs exhibit high capacity and excellent rate capability as anodes of LIBs, delivering a reversible capacity up to1083mA h g-1after50cycles at a rate of0.2C, and a capacity higher than305mA h g-1at a rate as high as10C. Moreover, the areal capacity of the NiO NSNs obtained here is as high as1.43mA h cm"2, which is276%and74%higher than nanostructured NiO and NiO nanocone arrays electrode, respectively.4. Mesoporous Co3O4NSNs with a thickness of～5.8μm were fabricated on Ni foam by a simple wet chemical method combined with subsequent calcination. It was shown that the NSNs exhibit excellent rate capability and cycling stability, but also a comparable areal capacity with the commercial value. It can deliver a reversible capacity up to4.39mA h cm-2(the corresponding specific capacity is1058mA h g-1) after30cycles at a current density of0.74mA cm-2, and a capacity higher than1.61mA h cm-2at a current density as high as7.38mA cm-2.