Titanium Carbide MXene Shows an Electrochemical Anomaly in Water-in-Salt Electrolytes

Xuehang Wang; Tyler S Mathis; Yangyunli Sun; Wan-Yu Tsai; Netanel Shpigel; Hui Shao; Danzhen Zhang; Kanit Hantanasirisakul; Fyodor Malchik; Nina Balke; De-En Jiang; Patrice Simon; Yury Gogotsi

doi:10.1021/acsnano.1c06027

Titanium Carbide MXene Shows an Electrochemical Anomaly in Water-in-Salt Electrolytes

ACS Nano. 2021 Sep 28;15(9):15274-15284. doi: 10.1021/acsnano.1c06027. Epub 2021 Aug 20.

Authors

Affiliations

¹ A. J. Drexel Nanomaterials Institute, and Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States.
² Department of Chemistry, University of California, Riverside, California 92521, United States.
³ Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
⁴ Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel.
⁵ Materials Science Department - CIRIMAT, Université Toulouse III Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, France.
⁶ Center for Physical and Chemical Methods of Research and Analysis, al-Farabi Kazakh National University, 050040 Almaty, Kazakhstan.
⁷ Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States.

PMID: 34415730
DOI: 10.1021/acsnano.1c06027

Abstract

Identifying and understanding charge storage mechanisms is important for advancing energy storage. Well-separated peaks in cyclic voltammograms (CVs) are considered key indicators of diffusion-controlled electrochemical processes with distinct Faradaic charge transfer. Herein, we report on an electrochemical system with separated CV peaks, accompanied by surface-controlled partial charge transfer, in 2D Ti₃C₂T_x MXene in water-in-salt electrolytes. The process involves the insertion/desertion of desolvation-free cations, leading to an abrupt change of the interlayer spacing between MXene sheets. This unusual behavior increases charge storage at positive potentials, thereby increasing the amount of energy stored. This also demonstrates opportunities for the development of high-rate aqueous energy storage devices and electrochemical actuators using safe and inexpensive aqueous electrolytes.

Keywords: abnormal electrochemical behavior; charge storage mechanism; desolvation-free cation insertion; partial charge transfer; titanium carbide MXene; water-in-salt electrolytes.