Coupling effects of F-doping and Se-vacancies on SnSe2 as an anode for LIBs guided by first-principles calculations

Abstract

SnSe₂, as a anode material with a theoretical specific capacity of up to 813 mAh g⁻¹ and a unique wide-spaced lamellar structure, has been regarded as a potential stock of anode for lithium-ion batteries. However, its inherent low electronic conductivity and bulk effect have been the key factors hindering its electrochemical performance. In this study, focusing on enhancing the intrinsic conductivity of SnSe₂, we innovatively introduced F-doping and Se-vacancies into its structure, successfully constructed F-SnSe_2-x crystals, and deeply explored the structural features and lithium storage properties of the crystals using first-principles calculation. Firstly, the phonon spectra and AIMD calculations verify the rationality and excellent thermal stability of the structure of F-SnSe_2-x. Besides, the F-SnSe_2-x crystal exhibits fast electron/lithium-ion transport kinetics, with a band gap value of 0.05 eV and a lithium-ion diffusion barrier of 0.24 eV, which predicts its excellent rate performance. In addition, the strong interaction between F-SnSe_2-x and lithium ions, manifested by a charge transfer of 0.53 eV and an adsorption energy of −8.3 eV, contributes to the cycling stability of the material. Finally, each F-SnSe_2-x molecule is capable of storing up to 4.5 Li atoms and corresponds to an average open-circuit voltage reaches 0.75 V, which provides a promising prospect for its application in high-energy-density lithium-ion batteries. This study is an important reference and inspiration for optimizing the lithium storage performance of SnSe₂ as well as other metal Se compounds.