First-Principles Study on the Structural, Electronic, and Lithium Storage Properties of TiCT (T = O, F, H, OH) MXene.

The structures of bare TiC and functionalized TiCT (T = O, F, H, OH) MXenes were constructed, and the effect of surface functional groups T (T = O, F, H, OH) on the structural, electronic, and lithium storage properties were investigated by first-principles calculations. The results show that the proximity of surface functional groups will induce some lattice distortion of TiCT MXene. The degree of lattice distortion depends mainly on the adsorption position of functional groups and the types of surface functional groups. From the point of view of forming energy, the surface functional groups tend to be located at the CCP site. From the energy band and DOS results, the presence of surface functional groups has a significant effect on the valence band, while it has a slight impact on the conduction band. In terms of lithium storage, lithium atom adsorption starts from the HCP position for bare TiC, while functionalized TiCT starts from the CCP position. The double-layer lithium storage capacity of bare TiC and TiCO were 639.78 mAh/g and 537.22 mAh/g, respectively. And the single-layer lithium storage capacity of TiCF was 130.77 mAh/g.