Investigation of two-dimensional hf-based MXenes as the anode materials for li/na-ion batteries: A DFT study

Density functional theory calculations are performed to investigate electronic properties and Li/Na storage capability of Hf₃ C₂ and its derivatives (uniform passivated: Hf₃ C₂ T₂ [T = F, O, OH] and hybrid passivated: Hf₃ C₂ F_x O_2-x and Hf₃ C₂ O_x (OH)_2-x [x = 1.0, 1.5]). For Hf₃ C₂ monolayer, it has excellent performance, such as good conductivity, low diffusion energy barrier, low open circuit voltage, and high storage capacities (Li(1034.70 mAh g^-1 ), Na(444.90 mAh g^-1 )), providing the most prospective as anode material. However, due to the unsaturated dangling bonds of surface Hf, so it is easily passivated. For the uniform passivated ones, Hf₃ C₂ T₂ , show higher diffusion barriers and lower storage capacities than bare monolayer Hf₃ C₂ . Nevertheless, compared with uniform passivated ones, the hybrid passivated derivative, Hf₃ C₂ F_1.5 O_0.5 and Hf₃ C₂ OOH possess a lower energy barrier and a better storage capacity. Therefore, Hf₃ C₂ F_1.5 O_0.5 and Hf₃ C₂ OOH are deemed to be a suitable candidate as anode electrode material for Li-ion batteries. © 2019 Wiley Periodicals, Inc.