Theoretical prediction of MXene-like structured TiC as a high capacity electrode material for Na ion batteries.

MXenes are attracting much attention as electrode materials due to their excellent energy storage properties and good electrical conductivity. Here a carbonized derivative of TiC (one representative MXene material), a TiC monolayer, is designed. Density functional theory (DFT) calculations were performed to investigate the geometric and electronic properties, dynamic stability, and Li/Na storage capability of TiC. The TiC monolayer is proved to be a structurally stable material showing the nature of the metal with C dimers rather than the individual C atom. Moreover, the TiC monolayer exhibits a low diffusion barrier and high storage capacity (up to TiCNa stoichiometry) in Na ion batteries (NIBs) compared with Li ion batteries (LIBs). Its superior properties, such as good electronic conductivity, fast Na diffusion, low open circuit voltage (OCV), and high theoretical Na storage capacity, make the TiC monolayer a promising anode material for NIBs. More importantly, similar to MXene TiC, new MC monolayers with C dimers can be formed by replacing M with other transition metal elements, and the properties of these monolayers are worthy of further study.