Long Cyclic Life in Manganese Oxide-Based Electrodes

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• 作者：Zhaoming Wang ; Qingqing Qin ; Wei Xu ; Jian Yan ; Yucheng Wu
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：July 20, 2016
• 年：2016
• 卷：8
• 期：28
• 页码：18078-18088
• 全文大小：910K
• 年卷期：0
• ISSN：1944-8252

文摘

Long cyclic life is very important to the practical application of the pseudocapacitors. A systematic study has been carried out to reveal what key factors and how they affecting the cycling behaviors of manganese oxides. The specific capacitance degradation of MnO_x is usually attributed to the so-called “dissolution” issue. Our results indicate that “dissoluted MnO_x” is in the form of the “flotsam” derived from the detached active materials instead of Mn²⁺ in the solution, which causes color change of electrolyte and the loss of specific capacitance. During the cycling, the morphology of manganese oxides transformed to flower-like flakes regardless of the starting structures. After that, it tends to form nanowires especially at elevated temperatures. According to the relative low electrochemical utility of nanowires, specific capacitance might decrease at this stage. These results put forward new questions on charge storage mechanism. Besides, electrochemical oxidation of MnO_x leads to an increase in specific capacitance. The cycling behavior of MnO_x is mainly determined by these three factors. Excitingly, a very stable cycling performance with no capacitance degradation over 40 000 cycles has been achieved in MnO₂ hierarchical sphere-based electrodes. This study provides insightful understanding of the fundamental cycling behavior of MnO_x-based electrodes and useful instructions for developing highly stable supercapacitors.