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Unveiling mechanism of sodium ion storage for needle-shaped ZnxCo3-xO4 nanosticks as anode materials

Abstract

The interest in the development of micro-nanostructured metal oxides has been increasing recently because of their advantages as electrode materials in energy storage applications. In this study, dandelion-like ZnxCo3-xO4 microspheres assembled with porous needle-shaped nanosticks were synthesized by co-precipitation followed by a post-annealing treatment. The open space between neighboring nanosticks enables easy infiltration of the electrolyte; therefore, each nanostick is surrounded by the electrolyte solution, which ensures proper utilization of the active material during electrochemical reaction. The dandelion-like ZnxCo3-xO4 hierarchical microspheres exhibit greatly improved electrochemical performance with high capacity and good cyclability as anodes for sodium-ion batteries (SIBs). A high initial reversible capacity of 612 mAh g–1 (at 35 mA g–1, ~0.04 C) is obtained and a capacity of 349 mAh g–1 retained after 200 cycles. Meanwhile, the electrode shows a high rate performance with a capacity of 246 mAh g–1 at 2.0 C-rate. The conversion of ZnxCo3-xO4 with Na is followed by ex situ X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) at different sodiation/de-sodiation states during electrochemical cycling. These analyses reveal that Na insertion/extraction is followed by complete reduction/oxidation of both metallic cobalt and zinc. Development of metallic Co and Zn after complete discharge and formation of Co3O4 and ZnO when the electrode was fully recharged were identified by ex situ TEM analysis. In addition, the ZnxCo3-xO4 anode demonstrates feasible operation in a full cell by pairing with a NaNi2/3Bi1/3O2 cathode, affording a SIB battery with an average working voltage of 2.6 V.

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Publication details

The article was received on 03 Nov 2018, accepted on 05 Dec 2018 and first published on 06 Dec 2018


Article type: Paper
DOI: 10.1039/C8NR08868C
Citation: Nanoscale, 2018, Accepted Manuscript
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    Unveiling mechanism of sodium ion storage for needle-shaped ZnxCo3-xO4 nanosticks as anode materials

    M. Islam, G. Ali, M. Jeong, H. Kim, W. Choi, K. Y. Chung and H. Jung, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR08868C

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