Are MXenes Promising Anode Materials for Li Ion Batteries? Computational Studies on Electronic Properties and Li Storage Capability of Ti₃C₂ and Ti₃C₂X₂ (X = F, OH) Monolayer

Density functional theory (DFT) computations were performed to investigate the electronic properties and Li storage capability of Ti₃C₂, one representative MXene (M represents transition metals, and X is either C or/and N) material, and its fluorinated and hydroxylated derivatives. The Ti₃C₂ monolayer acts as a magnetic metal, while its derived Ti₃C₂F₂ and Ti₃C₂(OH)₂ in their stable conformations are semiconductors with small band gaps. Li adsorption forms a strong Coulomb interaction with Ti₃C₂-based hosts but well preserves its structural integrity. The bare Ti₃C₂ monolayer exhibits a low barrier for Li diffusion and high Li storage capacity (up to Ti₃C₂Li₂ stoichiometry). The surface functionalization of F and OH blocks Li transport and decreases Li storage capacity, which should be avoided in experiments. The exceptional properties, including good electronic conductivity, fast Li diffusion, low operating voltage, and high theoretical Li storage capacity, make Ti₃C₂ MXene a promising anode material for Li ion batteries.