Electrochemical Properties of MXene Electrodes in Aqueous Zinc Electrolytes

MXenes are a family of two-dimensional (2D) transition metal carbonitrides, with a general structure of M_n+1X_nT_x, where M is the transition metal, X is carbon or nitrogen, T represents the surface terminations (F, O, OH), and n can vary from 1-4. MXenes have shown promise in multiple electrochemical systems including aqueous supercapacitors and non-aqueous batteries containing monovalent cations. However, there have been limited works studying the electrochemical properties of these materials in aqueous electrolytes with multivalent cations such as Zn²⁺ and Mg²⁺. MXenes have high (electro)chemical stability in halide zinc electrolyte systems unlike many oxide materials. Herein, the charge storage mechanism of Ti₃C₂T_x was studied in multiple Zn containing aqueous electrolytes. In-situ XRD and in-situ UV-Vis were employed to monitor the intercalating species and redox response in the electrodes. Ti₃C₂T_x electrodes could deliver battery-like performance at low rates with supercapacitor performance at high rates. This work demonstrates the potential of using MXenes in zinc ion capacitors and zinc hybrid energy storage devices.