First-principles calculation of a 1T-VS2/graphene composite as a high-performance anode material for lithium- and sodium-ion batteries

Abstract

Graphene and other conductive substrates have been used to improve the electrochemical efficiency of monolayer VS2, establishing it as a potential anode material for LIBs. Nonetheless, a detailed understanding of the synergistic relationship between VS2 and graphene (Gr), which is fundamental for boosting Li+/Na+ electrochemical storage device performance, remains limited. This study utilized density functional theory (DFT) computations to systematically analyze the VS2/Gr composite as an optimized electrode for Li+/Na+ electrochemical storage devices. Our findings reveal that VS2/Gr possesses outstanding structural stability, remarkable mechanical stiffness, strong ion adsorption ability, and enhanced charge transfer efficiency. Additionally, it exhibits a high theoretical storage capacity, a shallow average open-circuit voltage, and low ion diffusion barriers. The diffusion barriers of 0.11 eV for Li and 0.16 eV for Na are lower than those of widely studied composite materials, enabling an exceptionally fast Li+/Na+ diffusion rate during charge/discharge processes. The predicted open-circuit voltages for Li+/Na+ are 0.75 V and 0.77 V, respectively, with corresponding theoretical storage capacities reaching 1156 mAh g−1 for Li and 770 mAh g−1 for Na. These findings offer key insights for the experimental design and optimization of VS2/Gr anodes, paving the way for ultra-fast charging and high-capacity Li+/Na+ electrochemical storage devices.