Mechanism analysis of the capacitance contributions and ultralong cycling-stability of the isomorphous MnO2@MnO2 core/shell nanostructures for supercapacitors
Mechanism analysis of the capacitance contributions and ultralong cycling-stability of the isomorphous MnO2@MnO2 core/shell nanostructures for supercapacitors
复制标题
超级电容器同晶MnO2@MnO2核/壳纳米结构的电容贡献和超长循环稳定性的机理分析
DOI：
10.1039/c4ta06793b
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发表时间：
2015-01-01
影响因子：
11.9
通讯作者：
Hu, Junqing
中科院分区：
文献类型：
--
作者：
Shao, Jiajia;Zhou, Xiying;Hu, Junqing
利用二氧化锰纳米线作为种子晶体，首次建立了一种简便的合成MnO2@MnO2核/壳纳米结构的方法。这些独特的纳米结构由β - mno2纳米线表面生长的同构层组成，具有显著的电化学性能，具有高电容和超长的循环寿命，即在5 a g（-1）的电流密度下，在20,000次循环后保持近92.2%的保留率。MnO2@MnO2电极的比电容的提高主要是由双层充电和法拉第赝电容两种电容过程引起的。特别是，这些有趣的行为与MnO2纳米线芯和超薄MnO2纳米片壳之间独特的同构核/壳层结构、高机械稳定性以及良好的界面结构密切相关。此外，研究表明，在循环充放电初期，整个核/壳结构中缺陷区和无序区的形成是导致容量异常增加的主要原因。
A facile method to synthesize isomorphous MnO2@MnO2 core/shell nanostructures was developed for the first time by using MnO2 nanowires as seed crystals. These unique nanoarchitectures consisting of an isomorphous layer of beta-MnO2 nanosheets well grown on the surface of beta-MnO2 nanowires exhibit remarkable electrochemical performance with high capacitance and ultra long cycle life, i.e., nearly 92.2% retention after 20 000 cycles at a current density of 5 A g(-1). The enhanced specific capacitance of the MnO2@MnO2 electrode is largely contributed by the capacitive processes including double-layer charging and Faradaic pseudocapacity. Particularly, these intriguing behaviors are strongly correlated with the unique isomorphous core/shell hierarchical configuration and high mechanical stability as well as the better interfacial structures between the MnO2 nanowire core and the ultrathin MnO2 nanosheet shell. In addition, it is demonstrated that the formation of defective and disordered regions throughout the whole core/shell architecture is the main cause for the unusual increased capacity during the early stages of cyclic charge/discharge.