First-Principles Study on Introducing Fluorine Doping and Sulfur Vacancy into MoS2 for Advanced Lithium Storage

Abstract

MoS₂, a potential anode material for lithium ion batteries (LIBs), boasts high specific capacity, a unique layered structure, and large interlayer spacing, but struggles with poor conductivity and volume effect. Starting from improving the intrinsic electronic conductivity of MoS₂, this study innovatively introduces F-doping and sulfur vacancies into MoS₂ crystals to form F-MoS_2-x crystals, and investigates its structural features and LIBs applications through first-principle calculations. The rationality and stability of F-MoS_2−x are calculated by phonon spectra. The density of states calculations reveals that F-doping and sulfur vacancies effectively alter MoS₂'s electronic state, reducing its intrinsic band-gap and confirming F-MoS_2-x's superior electronic conductivity theoretically. They also significantly decrease lithium-ion diffusion resistance on F-MoS_2-x's surface, potentially enabling high-rate performance. Besides, the calculation of adsorption energy and differential charge density reveals strong adsorption between F-MoS_2-x and lithium ions, which favors long-term cycle stability. Notably, with each F-MoS_2-x molecule storing up to 4.5 Li, corresponding to a theoretical capacity of 769 mAh g⁻¹, higher than MoS₂'s 670 mAh g⁻¹. This study provides a meaningful reference value for the modification of MoS₂.