Abstract
This dissertation mainly focuses on reviewing and developing Ni-Co oxides/hydroxides for the application of aqueous supercapacitor and their asymmetric design, respectively, based on their unique and abundant physicochemical characteristics. In chapter 1, the background knowledge of energy technology, the characteristics and roles of supercapacitors, and the classification of supercapacitors were systematically discussed. After realizing the research background of aqueous supercapacitor and the newly developed asymmetric supercapacitor, the historical development of energy storage/delivery technology, preparation methods, the key issues that need to be considered, and the research motive for synthesizing Ni-Co oxides/hydroxides were summarized in chapter 2. All of the experimental materials, instruments, preparation procedures of active materials (including Ni-Co oxides/hydroxides and graphene), and the steps for constructing an asymmetric supercapacitor were listed in chapter 3 in detail. In chapter 4, the results and discussion sections have been divided into three parts, in order to figure out the different influences from the determining factors (such as crystal phase transformation degree or porous nanostructures) on the capacitive performance of Ni-Co oxides/hydroxides and to develop an operating strategy to achieve charge balance state for an asymmetric supercapacitor consist of one battery behavior electrode. A brief conclusion of this dissertation and the future prospects for Ni-Co oxides/hydroxides were presented in chapter 5. The future prospect for Ni-Co oxides/hydroxides should particularly be investigated on two aspects: employing them as electrochemical catalyst for metal-air battery due to their bi-functional oxygen evolution/reduction features, and developing a novel negative electrode active material (Fe(OH)3/AC composites) to replace the pure carbon materials for enhancing the stored energy of Ni-Co oxides/hydroxides based asymmetric supercapacitors.