Simple Cu2+ modification significantly improves the electrochemical performance of MXene (Ti3C2Tx) in aluminum batteries

Abstract

The MXene combines the dual characteristics of layered carbon materials and transition metal compounds, which is expected to promote the further development of emerging aluminum batteries. However, the rich functional groups and highly active Ti-ions (Ti2+ and Ti3+) on the surface of MXene result in a very complex mechanism of interaction with [AlCl4]−/Al3+, which affects its electrochemical behavior and energy storage mechanism in aluminum batteries. Herein, based on the self-reducing characteristic of MXene, a composite material Ti3C2Tx@Cu is prepared by modifying the surface functional groups and crystal structure of Ti3C2Tx with Cu2+. Through characterization of bulk phase (XRD), surface (XPS), and microstructure (SEM and TEM), it was demonstrated that the introduction of Cu2+ changed the surface physicochemical and crystal structure characteristics of MXene, improving its stability in aluminum batteries. Secondly, the electrochemical performance of Ti3C2Tx@Cu in aluminum batteries is studied. The initial charge/discharge specific capacity of the aluminum batteries is close to 400 mAh/g, and the specific capacity is still higher than 110 mAh/g after 1000 cycles. Finally, the energy storage mechanism of Ti3C2Tx@Cu in aluminum batteries is discussed. The electrochemical and physical characterization have shown that it mainly involves the intercalate/de-intercalate of [AlCl4]−, accompanied by conversion reaction of some Al3+/Al.