Enhanced Functional Properties of Ti3C2Tx MXenes as Negative Electrodes in Sodium‐Ion Batteries by Chemical Tuning

• Published in: Small methods 2020-09, Vol.4 (9), p.n/a
• Main Authors: Gentile, Antonio, Ferrara, Chiara, Tosoni, Sergio, Balordi, Marcella, Marchionna, Stefano, Cernuschi, Federico, Kim, Min‐Ho, Lee, Hyun‐Wook, Ruffo, Riccardo
• Format: Article
• Language: eng ; jpn
• Subjects: 2D materials; intercalation materials; layered materials; MXenes; titanium carbide
• ISSN: 2366-9608; 2366-9608
• DOI: 10.1002/smtd.202000314

The large implementation of electrochemical energy storage devices requires the development of new chemistries tailored for specific uses. Sodium‐ion batteries (SIBs) can cover different application fields, however the state‐of‐the‐art negative material, hard carbon, suffers from poor cyclability and rate capability. MXenes are a vast class of 2D‐materials of the general formula Mn+1XnTx (M = transition metal, X = C or N, and T = M‐terminating group) with peculiar structural features able to reversible intercalate chemical species, such as alkaline cations. The MXene compound Ti3C2Tx is one of the most investigated, thanks to the easy preparation route by etching of the pristine compound Ti3AlC2. In this work, the effect of the etching conditions and of the postsynthesis thermal treatments on the chemical, morphological, and structural properties of Ti3C2Tx are investigated, and in turn the correlation between its features and the functional properties as negative materials in SIBs are studied. The Ti3C2Tx obtained in high hydrofluoric concentration and after a 300 °C thermal treatment shows 110 mAh g−1 at 30 mA g−1 with an average potential of 1.33 V versus Na+/Na, 100% and good rate capability, since it is still able to deliver 73 mAh g−1 at 1500 mA g−1. Four Ti3C2Tx MXenes are prepared by tuning etching conditions and thermal treatments. The structure, composition, morphology, and the functional properties of the MXene as negative electrode in sodium‐ion batteries are investigated. The best performing electrodes are obtained using MXenes prepared in mild etching conditions or after thermal treatment at 300 °C.