Construction of Hierarchical α-MnO2 Nanowires@Ultrathin δ-MnO2 Nanosheets Core-Shell Nanostructure with Excellent Cycling Stability for High-Power Asymmetric Supercapacitor Electrodes
Construction of Hierarchical α-MnO2 Nanowires@Ultrathin δ-MnO2 Nanosheets Core-Shell Nanostructure with Excellent Cycling Stability for High-Power Asymmetric Supercapacitor Electrodes
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DOI：
10.1021/acsami.5b11300
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发表时间：
2016-04-13
影响因子：
9.5
通讯作者：
Shen, Dejiu
中科院分区：
文献类型：
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作者：
Ma, Zhipeng;Shao, Guangjie;Shen, Dejiu
低导电性和机械不稳定性是阻碍二氧化锰作为赝电容器材料实现高性能的两个主要因素。因此，构建独特的分级核壳纳米结构在有效提高该材料的速率容量和稳定性方面起着重要作用。本文报道了一种简单实用的液相合成技术，制备了α-MnO 2纳米线和α-MnO 2纳米片核壳结构的纳米材料。这种新型的分级纳米结构由α-MnO 2纳米片和少量的原子层组成，它们在超长的α-MnO 2纳米线表面生长良好。在20 A g（-1）的放电电流密度下，分级核壳纳米结构的首次比容量达到153.8 F g（-1），10000次充放电循环后的循环稳定性为98.1%，高于文献值。分级核壳纳米结构的优异的倍率容量和稳定性可以归因于两种MnO 2晶体的结构特征，其中1D α-MnO 2纳米线核提供稳定的结构骨架，而2D δ-MnO 2纳米片壳产生更多的反应活性位点。不同维度的协同效应也有助于获得优异的上级倍率性能。
Poor electrical conductivity and mechanical instability are two major obstacles to realizing high performance of MnO2 as pseudocapacitor material. The construction of unique hierarchical core-shell nanostructures, therefore, plays an important role in the efficient enhancement of the rate capacity and the stability of this material. We herein report the fabrication of a hierarchical alpha-MnO2 nanowires@ultrathin delta-MnO2 nanosheets core-shell nanostructure by adopting a facile and practical solution-phase technique. The novel hierarchical nanostructures are composed of ultrathin delta-MnO2 nanosheets with a few atomic layers growing well on the surface of the ultralong alpha-MnO2 nanowires. The first specific capacitance of hierarchical core-shell nanostructure reached 153.8 F g(-1) at the discharge current density of as high as 20 A g(-1), and the cycling stability is retained at 98.1% after 10 000 charge-discharge cycles, higher than those in the literature. The excellent rate capacity and stability of the hierarchical core-shell nanostructures can be attributed to the structural features of the two MnO2 crystals, in which a 1D alpha-MnO2 nanowire core provides a stable structural backbone and the ultrathin 2D delta-MnO2 nanosheet shell creates more reactive active sites. The synergistic effects of different dimensions also contribute to the superior rate capability.