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 Ti3C2Tx 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.
Bibliographical noteFunding Information:
This research was sponsored by the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science and Office of Basic Energy Sciences. Operando AFM measurements were carried out and supported at the Center for Nanophase Materials Sciences (CNMS) in Oak Ridge National Laboratory, which is a DOE Office of Science user facility. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231. The authors also acknowledge K. Li, C.E. Shuck and J. Tang (all, Drexel University) for assistance with SEM, ex-situ XRD, and Raman analyses.
© 2021 American Chemical Society.
- abnormal electrochemical behavior
- charge storage mechanism
- desolvation-free cation insertion
- partial charge transfer
- titanium carbide MXene
- water-in-salt electrolytes