Synthesis and Characterization of Nanostructure Electrodes for Lithium Ion Batteries

In the present thesis, several three-dimensional (3D) nanostructured composites with electrochemical active material/ 3D metallic current collector configurations have been investigated for their application as Li-ion battery (LIB) anode. A first attempt was made on metallic Cu/ CuO shell nanocable arrays anode, which was synthesized by partial oxidation of metallic Cu nanowire arrays. This composite electrode exhibited a high specific capacity, e.g. 840 mA h g-1 at 0.1 C rate, and excellent capacity retention ability. The enhanced electrochemical performance resulted from its short ionic/electronic transport pathways and excellent adhesion of the active material on current collector during cycling.;In order to further improve the anode capacity, Si was selected as the anode active material due to its high theoretical capacity (4200 mA h g -1). Metallic core/Si shell nanocable array configuration was firstly investigated. Such nanocable arrays were obtained by depositing a thin Si layer on metallic Ni nanowire arrays. Both magnetron sputtering and electrochemical deposition were found to be effective fabrication methodologies to form such cable-like nanostructured composite electrodes, which showed significantly improved electrochemical properties as LIB anode as compared to their thin film counterpart. The electrodeposition was found to be a superior method in forming uniform Si shell on the Ni nanowire surface, which had much better electrochemical performance than the sputtered nanocable electrode. It achieved a stable capacity of ~1900 mA h g-1 at 0.05 C, and ~1130 mA h g-1 at a higher rate of 1 C with good capacity retention. An optimal thickness of ~52 nm of the Si shell was identified for obtaining the best rate performance. On the other hand, N doping can be easily achieved using magnetron sputtering. It has been found that reduced interfacial resistance, enhanced effective Li ions diffusion coefficient in the active material, and more stable surface passivating layer were likely to be achieved by N doping, leading to an improvement of the rate performance and cyclability when compared to the undoped nanocable array counterpart.;The major problem associated with the nanocable configuration is its low area capacity. To pursue higher area capacity and better rate performance, an electrodeposited Ni/Si inverse opal composite, which can provide 3D bicontinuous pathways for ions/electrons transport, was designed as LIB anode. This type of electrode had larger active material loading capacity and exhibited lower interfacial resistance and higher effective Li ions diffusion coefficient when compared to the nanocable arrays electrode counterpart, resulting in the improvement of area capacities and rate capabilities.