Sc2CX (X=N2, ON, O2) MXenes as a promising anode material: A first-principles study

Abstract

MXenes’ tunable properties make them excellent candidates for many applications in future nanoelectronics. In this work, we explore the suitability of Sc2CX (X=N2, ON, O2) MXenes to act as the active anode materials in Na-ion based batteries (NIBs) by means of ab initio simulations. After analyzing the structural and elastic properties of all the possible models to evaluate the energetically favorable N and O functionalization sites, our calculations show that both Sc2CON and Sc2CN2 present a clear metallic character, making them potential candidates as anode materials. The investigation of the most relevant features for anode performance, such as the adsorption and diffusion of Na atoms, the intrinsic capacity, the open circuit voltage, and the storage capacity, shows that both systems are serious alternatives to the most common 2D materials currently employed in alkali metal batteries. In particular, Sc2CN2 presents better diffusion behavior thanks to the absence of Na clustering on its surface, with optimal diffusion barriers comparable to other 2D materials, such as MoN2, while the values of diffusion barriers for Sc2CON are at least three times smaller than those found for other anode candidates. Similarly, while the capacity of Sc2CON is close to the one reported for 2D Sc2C, Sc2CN2 possesses a power density more than twice higher than the ones of 2D materials, such as Sc2C, graphite, and MoS2. Our results, thus, confirm the urge for further experimental exploration of the MXene Sc2CX (X=N2, ON, O2) family as anode material in NIBs.