Electrochemical Energy Storage with MXenes

Since their discovery, MXenes have shown promising properties for electrochemical energy storage. In our group, we use different MXene compositions as electrodes and other components in different electrochemical systems such as supercapacitors and batteries to understand their electrochemical and charge storage behavior in various electrolytes including aqueous, water-in-salt, and organic ones. Our goal is to gain a deep understanding of the pseudocapacitive and intercalation properties of MXenes in these systems and optimize and design electrode architectures based on them for fast charge storage systems.”

1. Electrochemistry of MXenes and their hybrids in water-in-salt electrolytes

Since their discovery in 2011, MXenes have been widely explored for electrochemical energy storage devices such as supercapacitors and batteries. Their pseudocapacitive charge storage mechanism has been well-established in aqueous electrolytes, however, the energy density of MXenes is limited in aqueous electrolytes because of smaller electrochemically stable working windows. Recently, MXenes have been investigated in saturated water-in-salt electrolytes (WISE), which allows a wider working window, and a high energy density can be expected. In this direction, we have recently reported a saturated LiCl-WISE based electrochemical system exhibiting separated cyclic voltammogram (CV) peaks, accompanied by surface-controlled partial charge transfer in 2D Ti₃C₂T_x MXene. The process involves the insertion/desertion of desolvation-free cations (Li⁺), leading to an abrupt change of the interlayer spacing between MXene sheets. This unusual behavior increases the charge storage at positive potentials, thereby increasing the amount of energy stored. Currently, our group is exploring several WISEs on different MXenes and their hybrids.

Recent articles: Titanium Carbide MXene Shows an Electrochemical Anomaly in Water-in-Salt ElectrolytesACS Nano 2021, 15, 15274−15284Link: https://pubs.acs.org/doi/abs/10.1021/acsnano.1c06027

2. Lithium dendrite suppression with MXene current collectors

MXenes as current collectors have shown promises to suppress dendrite formation during lithium deposition. This property could foster the development of lithium-metal batteries, which could improve the energy density at least 30% beyond the state-of-the-art lithium-ion batteries. Our current goal is to find the practical current density and capacity range that can sustain the dendrite-free deposition of lithium metal and understand the fundamental properties of MXenes that lead to this behavior.

3. MXene-based 2D materials for Lithium-Sulfur batteries

Leading group members: Ruocun (John) Wang, Mohit Saraf, Kyle Matthews, Geetha Valurouthu

Reference: VahidMohammadi, Armin, Johanna Rosen, and Yury Gogotsi. “The world of two-dimensional carbides and nitrides (MXenes).” Science 372.6547 (2021): eabf1581.