Two-dimensional carbides and nitrides of transition metals, known as MXenes, are a fast-growing family of materials that have attracted attention as energy storage materials. MXenes are mainly prepared from Al-containing MAX phases (where A = Al) by Al dissolution in F-containing solution; most other MAX phases have not been explored. Here a redox-controlled A-site etching of MAX phases in Lewis acidic melts is proposed and validated by the synthesis of various MXenes from unconventional MAX-phase precursors with A elements Si, Zn and Ga. A negative electrode of Ti3C2 MXene material obtained through this molten salt synthesis method delivers a Li+ storage capacity of up to 738 C g−1 (205 mAh g−1) with high charge–discharge rate and a pseudocapacitive-like electrochemical signature in 1 M LiPF6 carbonate-based electrolyte. MXenes prepared via this molten salt synthesis route may prove suitable for use as high-rate negative-electrode materials for electrochemical energy storage applications.
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This study was supported financially by the National Natural Science Foundation of China (grant nos. 21671195, 91426304, 51902320 and 51902319) and by the China Postdoctoral Science Foundation (grant no. 2018M642498). H.S. was supported by a grant from the China Scolarship Council. P.S., P.L.T. and H.S. thank the Agence Nationale de la Recherche (Labex STORE-EX) for financial support. Q.H. thanks the International Partnership Program of Chinese Academy of Sciences (grant no. 174433KYSB20190019), the Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang, and the Ningbo top-talent team program for financial support. Z.L. is supported by the Fundamental Research Funds for the Central Universities (grant no. YJ201886). We acknowledge the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (faculty grant SFO‐Mat‐LiU no. 2009 00971). The Knut and Alice Wallenberg Foundation is acknowledged for support of the electron microscopy laboratory in Linköping, a Fellowship grant (P.E) and a scholar grant (L.H., 2016-0358).
The authors declare no competing interests.
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Li, Y., Shao, H., Lin, Z. et al. A general Lewis acidic etching route for preparing MXenes with enhanced electrochemical performance in non-aqueous electrolyte. Nat. Mater. (2020). https://doi.org/10.1038/s41563-020-0657-0