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Materials 2017, 10(9), 988;

Enhanced Cycleability of Amorphous MnO2 by Covering on α-MnO2 Needles in an Electrochemical Capacitor

School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, China
College of Biological, Chemical Science and Chemical Engineering, Jiaxing University, Jiaxing 314001, China
Institute of Chemical Engineering, Qingdao University of Science and Technology, Qingdao 266042, China
Renewable Energy Group, Department of Energy and Process Engineering, Faculty of Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway
Authors to whom correspondence should be addressed.
Received: 13 July 2017 / Revised: 9 August 2017 / Accepted: 10 August 2017 / Published: 24 August 2017
(This article belongs to the Special Issue Energetic Materials and Processes)
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An allomorph MnO2@MnO2 core-shell nanostructure was developed via a two-step aqueous reaction method. The data analysis of Scanning Electron Microscopy, Transmission Electron Microscopy, X-Ray Diffraction and N2 adsorption-desorption isotherms experiments indicated that this unique architecture consisted of a porous layer of amorphous-MnO2 nano-sheets which were well grown onto the surface of α-MnO2 nano-needles. Cyclic voltammetry experiments revealed that the double-layer charging and Faradaic pseudo-capacity of the MnO2@MnO2 capacitor electrode contributed to a specific capacitance of 150.3 F·g−1 at a current density of 0.1 A·g−1. Long cycle life experiments on the as-prepared MnO2@MnO2 sample showed nearly a 99.3% retention after 5000 cycles at a current density of 2 A·g−1. This retention value was found to be significantly higher than those reported for amorphous MnO2-based capacitor electrodes. It was also found that the remarkable cycleability of the MnO2@MnO2 was due to the supporting role of α-MnO2 nano-needle core and the outer amorphous MnO2 layer. View Full-Text
Keywords: manganese dioxide; core-shell structure; porous; electrochemical capacitors; long stability manganese dioxide; core-shell structure; porous; electrochemical capacitors; long stability

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Liu, Q.; Ji, S.; Yang, J.; Wang, H.; Pollet, B.G.; Wang, R. Enhanced Cycleability of Amorphous MnO2 by Covering on α-MnO2 Needles in an Electrochemical Capacitor. Materials 2017, 10, 988.

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