title: Construction of Hierarchical α-MnO2 Nanowires@Ultrathin δ-MnO2 Nanosheets Core-Shell Nanostructure with Excellent Cycling Stability for High-Power Asymmetric Supercapacitor Electrodes.
abstract: 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 α-MnO2 nanowires@ultrathin δ-MnO2 nanosheets core-shell nanostructure by adopting a facile and practical solution-phase technique. The novel hierarchical nanostructures are composed of ultrathin δ-MnO2 nanosheets with a few atomic layers growing well on the surface of the ultralong α-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 α-MnO2 nanowire core provides a stable structural backbone and the ultrathin 2D δ-MnO2 nanosheet shell creates more reactive active sites. The synergistic effects of different dimensions also contribute to the superior rate capability.
authors.affiliation: College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao 066004, China.|State Key Laboratory of Metastable Materials Science and Technology, Yanshan University , Qinhuangdao 066004, China.
authors.forename: Zhipeng
authors.initials: Z
authors.lastname: Ma
authors.affiliation: College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao 066004, China.|State Key Laboratory of Metastable Materials Science and Technology, Yanshan University , Qinhuangdao 066004, China.
authors.forename: Guangjie
authors.initials: G
authors.lastname: Shao
authors.affiliation: College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao 066004, China.
authors.forename: Yuqian
authors.initials: Y
authors.lastname: Fan
authors.affiliation: College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao 066004, China.
authors.forename: Guiling
authors.initials: G
authors.lastname: Wang
authors.affiliation: College of Environmental and Chemical Engineering, Yanshan University , Qinhuangdao 066004, China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Song
authors.affiliation: State Key Laboratory of Metastable Materials Science and Technology, Yanshan University , Qinhuangdao 066004, China.
authors.forename: Dejiu
authors.initials: D
authors.lastname: Shen
keywords: core−shell nanostructures; cycling stability; manganese dioxide; nanosheets; nanowires; supercapacitors