(Invited) MXenes for High-Energy, High-Power Batteries and Electrochemical Capacitors

Abstract

Two-dimensional (2D) nanomaterials have been attractive candidates for a plethora of applications since the successful isolation and demonstration of intriguing electronic properties of graphene in 2004 by the Manchester group. The ‘beyond graphene’ march led to the discovery of new types of conductive 2D materials, expanding the use of low-dimensional nanomaterials in electrochemical energy storage and conversion. MXenes are a relatively new and very large family of 2D transition metal carbides, nitrides, and carbonitrides, which were discovered at Drexel in 2011 and became popular due to their diverse chemistries and unique physicochemical properties. These materials are produced by wet chemical or electrochemical extraction of interleaved ‘A’ atomic layers from the layered ternary carbide or nitride precursors. The resulting MXenes with surface terminations (-O, -F, -OH, -Cl) impart negative surface charges, key for stable MXene dispersions in water and organic solvents, which enable solution processing. More than 30 different MXenes have been experimentally synthesized, with dozens of new MXenes and their properties predicted computationally. The compositional versatility, metallic conductivity, control of surface chemistry, ordered structures versus solid solutions, etc., make MXenes suitable for a wide spectrum of applications in energy storage, ranging from battery and supercapacitor electrodes to current collectors and conductive binders. The available for ion transport 2D gallery spaces, redox chemistry at the transition metal oxide-like surface and metallic conductivity provided by electrons of the transition metals, make MXenes promising as candidates for high-rate energy storage applications. The ability of MXenes to spontaneously intercalate a variety of cations, from Li+ to Al3+, while promoting fast charge transfer rates, endorses them for hybrid metal-ion capacitors and battery applications. Unlike most of the 2D materials produced in small quantities, pilot scale synthesis of MXenes is a promising aspect for future commercialization. This presentation will describe the potential use of MXenes in metal-ion capacitors, Li-ion and Li-S batteries as materials for anodes and cathodes. The use of MXenes to eliminate polymer binders and metal current collectors will also be addressed.