Potential Applications of Heterostructures of TMDs with MXenes in Sodium-Ion and Na–O₂ Batteries

Abstract

Na-ion batteries are viewed as the alternative to Li-ion batteries for similar electrochemical properties, while they always suffer from a low capacity. Na-O₂ batteries are important due to their high energy density; however, they are usually limited by high overpotential. In this manuscript, 16 different heterostructures of TMDs with MXenes (bare and O-terminated case) are constructed and their potential in the application of sodium-ion batteries (SIBs) and Na-O₂ batteries is explored. Among these structures, it is proved that only the heterostructures of VS₂ with O-terminated MXenes could load five layers of Na⁺ ions, while the others will have a distortion when Na⁺ ions intercalate or diffuse in the interlayer or the second adsorption layer. The ultrasmall diffusion barrier of Na⁺ ion denotes that these structures have a fast charge/discharge speed, and the ultrasmall open circuit voltages (OCVs) of 0.18 and 0.21 V prove that they are promising candidates for SIBs. The ultralow overpotential 0.55 V/0.20 V for the η_ORR/η_OER means that the O facet of the VS₂/Ti₂CO₂ heterostructure also has a great potential in the application of Na-O₂ batteries. These simulations prove that the heterostructures constructed by TMDs with MXenes have great potential in SIBs and Na-O₂ batteries and are important for future battery design.