To explore if the unique properties of the Ti3C2Tx MXene makes it a suitable anode material for Li-ion batteries, we have performed a detailed study of the electrochemical behavior of a freestanding Ti3C2Tx electrode. The latter did not contain any binder nor conductive additive and was manufactured by vacuum filtration of MXene suspension in DI water. The testing was performed in a half cell containing a Li-metal electrode and 1 M LiPF6 in EC:DEC (50:50 vol%) as the electrolyte. As the mechanism of charge storage in MXenes is still open for discussion, the focus was on which electrochemical reactions could be responsible for observed specific capacity seen for the freestanding Ti3C2Tx electrode. Electrochemical constant current and voltammetric cycling, ex-situ XPS, HAXPES and XAS were used to identify the processes taking place when charging and discharging the MXene electrode. Our results reveal that the double layer capacity cannot explain the observed reversible capacity and that the latter instead originates from electrochemical reactions (i.e. Faradaic reactions) involving oxidized Ti states present on the MXene surface. Results obtained with XAS (a technique that is more sensitive to the change of the oxidation state than both XPS and HAXPES) in transmission mode demonstrate that the Ti redox reactions are surface confined and that the redox reactions hence do not involve the bulk of the MXene present in the electrode. The irreversible capacity observed on the first cycle was attributed to reduction of water confined between MXene nanosheets. This poster presents the obtained experimental results in relation to earlier published data on Ti3C2Tx MXenes and anodes for lithium-based batteries.

Ti3C2Tx MXene as an Li-ion battery anode material

ACS Fall 2021

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