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

ABSTRACT

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 Fx O2-x and Hf3 C2 Ox (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 F1.5 O0.5 and Hf3 C2 OOH possess a lower energy barrier and a better storage capacity. Therefore, Hf3 C2 F1.5 O0.5 and Hf3 C2 OOH are deemed to be a suitable candidate as anode electrode material for Li-ion batteries. © 2019 Wiley Periodicals, Inc.