Advantage of Larger Interlayer Spacing of a Mo2Ti2C3 MXene Free-Standing Film Electrode toward an Excellent Performance Supercapacitor in a Binary Ionic Liquid–Organic Electrolyte

• Published in: ACS omega Vol. 7; no. 8; pp. 7190 - 7198
• Main Authors: Gandla, Dayakar, Zhang, Fuming, Tan, Daniel Q
• Format: Journal Article
• Language: English
• Published: American Chemical Society 01.03.2022
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.1c06761

MXenes show outstanding specific capacitance in aqueous electrolytes. However, the narrow potential window of aqueous electrolytes restrains the energy density. Ionic liquid electrolytes can provide a higher potential window and superior specific energy but are subject to slow ion transport and difficult intercalation for their larger ion size. It is desirable to explore larger interlayer-spaced (d-spaced) MXenes that can facilitate the large ion intercalation–deintercalation process. This work reports the first-ever supercapacitor application of the Mo2Ti2C3 MXene free-standing film electrode (f-Mo2Ti2C3) using 1 M 1-ethyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)-imide (EMIMTFSI) in acetonitrile electrolyte. Without any preintercalating agents, the authors achieved an interlayer spacing of ∼2.4 nm in the f-Mo2Ti2C3 material through etching, followed by a vacuum-assisted filtration technique. The microstructure, electrochemical properties, and charge storage kinetics of the f-Mo2Ti2C3 outperform the conventional f-Ti3C2T x . The f-Mo2Ti2C3-based symmetric two-electrode device exhibited remarkable specific energy and specific power of 188 Wh kg–1 and 22 kW kg–1, respectively, along with a high specific capacitance of 152 F g–1. This larger d-spaced f-Mo2Ti2C3 can emerge as a better alternative to the conventional f-Ti3C2T x in ionic liquid electrolytes to design next-generation high-performance MXene supercapacitors.