3 years ago

Na-Ion Intercalation and Charge Storage Mechanism in 2D Vanadium Carbide

Na-Ion Intercalation and Charge Storage Mechanism in 2D Vanadium Carbide
Xiqian Yu, Sungsik Lee, Wanli Yang, Ruimin Qiao, Yury Gogotsi, Xiao-Qing Yang, Hungsui Lee, Babak Anasori, Seong-Min Bak
2D vanadium carbide MXene containing surface functional groups (denoted as V2CTx, where Tx are surface functional groups) is synthesized and studied as anode material for Na-ion batteries. V2CTx anode exhibits reversible charge storage with good cycling stability and high rate capability through electrochemical test. The charge storage mechanism of V2CTx material during Na+ intercalation/deintercalation and the redox reaction of vanadium are studied using a combination of synchrotron based X-ray diffraction, hard X-ray absorption near edge spectroscopy (XANES), and soft X-ray absorption spectroscopy (sXAS). Experimental evidence of a major contribution of redox reaction of vanadium to the charge storage and the reversible capacity of V2CTx during sodiation/desodiation process are provided through V K-edge XANES and V L2,3-edge sXAS results. A correlation between the CO32− content and the Na+ intercalation/deintercalation states in the V2CTx electrode observed from C and O K-edge in sXAS results implies that some additional charge storage reactions may take place between the Na+-intercalated V2CTx and the carbonate-based nonaqueous electrolyte. The results of this study provide valuable information for the further studies on V2CTx as anode material for Na-ion batteries and capacitors. Na-ion intercalation and charge storage mechanism of 2D vanadium carbide MXene are investigated by using a combination of synchrotron-based X-ray techniques. It is demonstrated, for the first time, that the redox reaction at the transition metal site in MXene is responsible for the reversible charge storage. The reversible formation/decomposition of carbonate species at the surface upon sodiation/desodiation is also discussed in detail.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201700959

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