Mechanical Properties, Electronic Structures, and Potential Applications in Lithium Ion Batteries: A First-Principles Study toward SnSe2 Nanotubes

First-principles calculations were carried out to investigate the mechanical and electronic properties as well as the potential application of SnSe2 nanotubes. It was found that the mechanical properties are closely dependent on diameter and chirality: the Youngs modulus (Y) increases with the enlargement of diameter and converges to the monolayer limit when the diameter reaches a certain degree; with a comparable diameter, the armchair nanotube has a larger Youngs modulus than the zigzag one. The significantly higher Youngs modulus of SnSe2 nanotubes with the larger diameter demonstrates that the deformation does not easily occur, which is beneficial to the application as anode materials in lithium ion batteries because a large volume expansion during chargedischarge cycling will result in serious pulverization of the electrodes and thus rapid capacity degradation. On the other hand, band structure calculations unveiled that SnSe2 nanotubes display a diversity of electronic properties, which are also diameter- and chirality-dependent: armchair nanotubes (ANTs) are indirect bandgap semiconductors, and the energy gaps increase monotonously with the increase of tube diameter, while zigzag nanotubes (ZNTs) are metals. The metallic SnSe2 ZNTs exhibit terrific performance for the adsorption and diffusion of Li atom, thus they are very promising as anode materials in the Li-ion batteries.