Abstract
Nanostructured core/shell electrodes have been experimentally demonstrated promising for high-performance electrochemical energy storage devices. However, chemical insights into the significant roles of nanowire cores on the growth of shells and their supercapacitor behaviors still remain as a research shortfall. In this work, by substituting 1/3 cobalt in the Co3O4 nanowire core with nickel, a 61% enhancement of the specific mass-loading of the Ni(OH)2 shell, a tremendous 93% increase of the volumetric capacitance and a superior cyclability were achieved in a novel NiCo2O4/Ni(OH)2 core/shell electrode in contrast to a Co3O4/Ni(OH)2 one. A comparative study suggested that not only the growth of Ni(OH)2 shells but also the contribution of cores were attributed to the overall performances. Importantly, their chemical origins were revealed through a theoretical simulation of the core/shell interfacial energy changes. Besides, asymmetric supercapacitor devices and applications were also explored. The scientific clues and practical potentials obtained in this work are helpful for the design and analysis of alternative core/shell electrode materials.
Highlights
Nanostructured core/shell electrodes have been experimentally demonstrated promising for highperformance electrochemical energy storage devices
It is clear that the Co3O4 and NiCo2O4 nanowires are well assembled with 3D network architectures, which are favorable to provide large surface areas for further active material growth
Co3O4/NiSO4·6H2O and CoSO4·7H2O (Ni)(OH)[2] and NiCo2O4/Ni(OH)[2] core/shell structures were successfully prepared on nickel form substrate through hydrothermal and chemical bath depositions
Summary
Nanostructured core/shell electrodes have been experimentally demonstrated promising for highperformance electrochemical energy storage devices. The Ni, Co oxides based cores are of great interests, because they not just serve as an agent to increase the surface area and contribute to the total capacitance owing to their own high electrochemical activities[40,42,43,44,45,46,47,48,49]. We carried out a comparative study on supercapacitor performances for the core/shell structures of Ni(OH)[2] grown on two different nanowires: NiCo2O4 and Co3O4. The capacitance retention enhanced to 96.5% for the NiCo2O4/Ni(OH)[2] electrode compared with the Co3O4/Ni(OH)[2] (74.4%) after 1000 cycles Both the enhancement of the specific mass-loading of the Ni(OH)[2] shell and the more electrochemically active NiCo2O4 core contributed to its superior performances. The experimental evidences and scientific understandings achieved in this work are of great values for the design and interpretation of other core/shell systems
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