Synthesis and electrochemical properties of V 2 C MXene by etching in opened/closed environments
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ISSN 2226-4108 CN 10-1154/TQ
Research Article
Synthesis and electrochemical properties of V2C MXene by etching in opened/closed environments Meng WU, Yan HE, Libo WANG, Qixun XIA*, Aiguo ZHOU* Henan Key Laboratory of Materials on Deep-Earth Engineering, School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China Received: May 09, 2020; Revised: August 12, 2020; Accepted: August 13, 2020 © The Author(s) 2020.
Abstract: The effect of etching environment (opened or closed) on the synthesis and electrochemical properties of V2C MXene was studied. V2C MXene samples were synthesized by selectively etching of V2AlC at 90 ℃ in two different environments: opened environment (OE) in oil bath pans under atmosphere pressure and closed environment (CE) in hydrothermal reaction kettles under higher pressures. In OE, only NaF (sodium fluoride) + HCl (hydrochloric acid) etching solution can be used to synthesize highly pure V2C MXene. However, in CE, both LiF (lithium fluoride) + HCl and NaF+HCl etchant can be used to prepare V2C MXene. Moreover, the V2C MXene samples made in CE had higher purity and better-layered structure than those made in OE. Although the purity of V2C obtained by LiF+HCl is lower than that of V2C obtained using NaF+HCl, it shows better electrochemical performance as anodes of lithium-ion batteries (LIBs). Therefore, etching in CE is a better method for preparing highly pure V2C MXene, which provides a reference for expanding the synthesis methods of V2C with better electrochemical properties. Keywords: V2C MXene; etching environment; oil bath pan; hydrothermal reaction kettle; lithium-ion battery (LIB)
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Introduction
MXenes is a family of novel two-dimensional materials that was successfully synthesized in 2011 [1]. MXene was prepared by exfoliating the A-group element from the MAX phase [1–6] with a formula of Mn+1AXn, where M is an early transition metal, A is an III or IV A-group element, and X is C and/or N. Because － MXenes were made in an aqueous solution of F , the surfaces of MXenes are always terminated with F, O, * Corresponding authors. E-mail: A. Zhou, [email protected]; Q. Xia, [email protected]
and OH [7–9]. Ti3C2 is the first extensively studied MXene [1] and widely applied in energy storage [10–17]. Besides Ti3C2 MXene, V2C is another MXene that attracts the attention of many researchers, which has better performance as an anode of lithium-ion batteries (LIBs) than many other MXenes based on theoretical calculation [18]. V2C MXene is an ideal electrode material for LIBs with the theoretical capacity of 940 mAh·g–1, which is much higher than that of MXenes (Ti3C2 and Nb2C) or commercial graphite (372 mAh·g–1), though it is widely used in energy storage and other fields [19–23]. Although V2C MXene has good performance in many areas, highly pure V2C is difficult to be made.
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J Adv Ceram 2020, 9(6): 0–0
The conventional method to obtain V2C is to etching V2AlC by HF solution at room temperature [24,25]. However, the V2C
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