Sodium ion storage performance and mechanism in orthorhombic V 2 O 5 single-crystalline nanowires
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Published online 13 October 2020 | https://doi.org/10.1007/s40843-020-1468-6
Sodium ion storage performance and mechanism in orthorhombic V2O5 single-crystalline nanowires 1,2
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Yanwei Li , Jingcheng Ji , Jinhuan Yao , Ying Zhang , Bin Huang and Guozhong Cao ABSTRACT A fundamental understanding of the electrochemical reaction process and mechanism of electrodes is very crucial for developing high-performance electrode materials. In this study, we report the sodium ion storage behavior and mechanism of orthorhombic V2O5 single-crystalline nano+ wires in the voltage window of 1.0–4.0 V (vs. Na/Na ). The single-crystalline nanowires exhibit a large irreversible capacity loss during the first discharge/charge cycle, and then show excellent cycling stability in the following cycles. At a current −1 density of 100 mA g , the nanowires electrode delivers initial −1 discharge/charge capacity of 217/88 mA h g , corresponding to a Coulombic efficiency of only 40.5%; after 100 cycles, the electrode remains a reversible discharge capacity of −1 78 mA h g with a fading rate of only 0.09% per cycle comnd pared with the 2 cycle discharge capacity. The sodium ion storage mechanism was investigated, illustrating that the large irreversible capacity loss in the first cycle can be attributed to the initially formed single-crystalline α'-NaxV2O5 (0.02 < x < 0.88), in which sodium ions cannot be electrochemically extracted and the α'-Na0.88V2O5 can reversibly host and release sodium ions via a single-phase (solid solution) reaction, + leading to excellent cycling stability. The Na diffusion coef−12 −11.5 2 −1 ficient in α'-NaxV2O5 ranges from 10 to 10 cm s as evaluated by galvanostatic intermittent titration technique (GITT). Keywords: sodium ion batteries, V2O5, single-crystalline, nanowires, sodium storage mechanism
INTRODUCTION Currently, lithium-ion batteries (LIBs) are widely employed in portable electronic devices, electrical vehicles, and grid energy storage due to their high-power density, large energy density, and long lifespan [1,2]. However, the low abundance (only 0.0017 wt% in the earth’s crust) of
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Li resource is a great obstacle for the massive development of LIBs in large-scale energy storage applications [3]. In this context, sodium-ion batteries (SIBs) are expected to be one of the most promising candidates for post LIBs because of the abundant resource of Na (~2.83 wt% in the earth’s crust) and the similar chemical prop+ erties of Na and Li [4,5]. The radius of Na (1.02 Å) is + much larger than that of Li (0.76 Å), which leads to sluggish sodiation/desodiation reaction kinetics and poor cycling performance. The exploration of high-performance electrodes is crucial for the development of SIBs [6,7]. To date, a large number of cathode materials, including layered transition-metal oxides [8], polyanion cathodes [9], Prussian blue analogs [10], and organic compounds [11] for SIBs have been explored. Among these potential cathode materials for SIBs, vanadium oxides have attracted more attention owing to
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