Novel Nanomaterials for High Mass-loading Electrodes towards Supercapacitors with Superior Performances

用於高性能超級電容器的高載量新型納米電極材料

Student thesis: Doctoral Thesis

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Award date9 Jan 2019

Abstract

Realization of superior energy density is a critical demand for the practical applications of supercapacitors. The energy density of supercapacitor devices has been mainly limited by two factors: 1) the low utilization of active materials on pseudocapacitive or battery-type positive electrodes, and 2) the low specific capacitance values of carbon-based negative electrodes. At present, nanostructured transition metal hydroxides become desirable positive electrode materials due to their high redox reversibility, high capacitance, and cost-effectiveness. While for the carbon-based negative electrodes, biomass-derived carbon materials with high surface area, good conductivity and environmental friendliness are considered as promising candidates.

This thesis presents four continuous researches concerning positive and negative electrode materials for supercapacitors. To begin with, a novel seed-assisted method is presented to prepare Ni-Co-Mn hydroxides (NCMH) for supercapacitor applications. Excellent performances of this material lead to the curiosity of further study, in which DFT simulation is applied to predicate the doping process of multi-elemental LDHs in a later chapter. As a result, a new inverse-doping Ni/Zn-Co-Al LDH (N/ZCA) is successfully predicated and synthesized as a proof-of-concept. After the success in the preparation of positive electrodes, two other researches focus on the preparation of negative carbon materials. The first one develops a facial and environment-friendly process to convert biowaste corncrib to hierarchical porous carbon (HPC), which is applied in a symmetric supercapacitor. Concerning this success in biowaste-converted carbon, a later chapter deeply studies the selection of different biological procures (corncob woody ring and pith) and electrolytes (KOH liquid and PVA solid ones). Lastly, the as-obtained two materials (HPC//NCMH) are paired with each other to fabricate a high-performance asymmetric supercapacitor.