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

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.

Robust Bioinspired MXene–Hemicellulose Composite Films with Excellent Electrical Conductivity for Multifunctional Electrode Applications

“…Emerging flexible electronics have greatly stimulated the demand for structural electrode materials with integrated high electrical conductivity and mechanical strength for multifunctional applications . Ti 3 C 2 T x , the first member of the MXenes with metallic conductivity and mixed surface terminations, has stimulated a wide range of innovations, such as electrochemical energy storage, optoelectronics, and electromagnetic interference shielding. − However, the fragile nature of pristine MXene films, due to the poor interaction between adjacent nanosheets, restricts their applications in structural electrode materials.…”

Surface Redox Pseudocapacitance of Partially Oxidized Titanium Carbide MXene in Water-in-Salt Electrolyte

“…Pristine Ti 3 C 2 T x was oxidized in situ in a 19.2 m (mol/kg of solvent) LiBr WIS electrolyte by cyclic voltammetry between 0 and 1.2 V vs Ag at a scan rate of 2 mV/s (Figure S1a). Notably, Ti 3 C 2 T x is electrochemically stable up to 0.8 V vs Ag in 19.2 m LiBr . X-ray diffraction (XRD) shows the (002) peak of Ti 3 C 2 T x before and after three oxidation cycles (Figure a).…”

Microscopic Simulations of Electrochemical Double-Layer Capacitors

“…For example, the introduction of water-in-salts, which are highly concentrated aqueous electrolytes, opens the way toward aqueous devices with better performance. They are characterized by the formation of complex nanostructures in the liquid state, , and an interesting interplay between these structures and the porosity of EDLC electrodes has been observed experimentally, which remains to be investigated using molecular simulations. Biredox ionic liquids also are a promising lead for devices with increased energy densities .…”