After obtaining Ti${}_3$C${}_2$ MXene structures terminated with O, S, Se, F, Cl, and Br, we calculate the energy barrier for Li-ion diffusion on the surface of each MXene, being the first to report on the Li-ion diffusivity in Cl and Br terminated Ti${}_3$C${}_2$. We find that the Ti${}_3$C${}_2$Cl${}_2$ MXene has the lowest diffusion barrier, substituting the Ti${}_3$C${}_2$S${}_2$ reported in the literature so far. In addition, a study on the adsorption energies indicates that the top binding position is the most stable adsorption position for the Li-ion. Furthermore, it is shown that the adsorption energy depends on the electronegativity of the termination atoms, as well as the distance between the terminations, the Li, and the surface Ti-atoms. Finally, we show that the bond valence sum method provides an indication of the transition state of the Li-ion and can serve as a comparison tool for the diffusion barriers of different structures.

中文翻译：

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锂离子在 Ti3C2–T 表面的行为（T = O、S、Se、F、Cl、Br）MXene：扩散势垒和导电通路

获得Ti后${}_3$C${}_2$ MXene 结构以 O、S、Se、F、Cl 和 Br 终止，我们计算了每个 MXene 表面锂离子扩散的能垒，这是第一个报告锂离子在 Cl 和 Br 终止的扩散率钛${}_3$C${}_2$. 我们发现 Ti${}_3$C${}_2$氯${}_2$ MXene 具有最低的扩散势垒，取代了 Ti${}_3$C${}_2$秒${}_2$迄今文献报道。此外，对吸附能的研究表明，顶部结合位置是锂离子最稳定的吸附位置。此外，研究表明吸附能取决于末端原子的电负性，以及末端、锂和表面钛原子之间的距离。最后，我们表明键价和方法提供了锂离子过渡态的指示，并可作为不同结构扩散势垒的比较工具。