Two-Dimensional α-SiX (X = N, P) Monolayers as Efficient Anode Material for Li-Ion Batteries: A First-Principles Study

Density functional theory simulations were performed to investigate the structural, electronic, and electrochemical properties of the two-dimensional alpha SiX (X = N, P) monolayers as anode material in Li-ion batteries (LIBs). Our result indicates that alpha-SiX monolayers have excellent mechanical, dynamical, and thermal stability. The obtained adsorption energy values suggest that the Li atom adsorption over alpha-SiX is a favorable process. According to the Lo''wdin charge transfer and partial density of states analysis, charge transfer takes place from Li atom to alpha-SiX monolayers. From the band structure plots, we observed that after the adsorption of a single Li atom, the alpha-SiX monolayers are converted into a metallic state from the semiconductor state and remain in the metallic state for the different adsorption concentrations of Li atoms, which is essential to facilitate the diffusion of stored electrons. The calculated specific storage capacity is 956.16 and 733.66 mA h g(-1) for alpha-SiN and alpha-SiP monolayers, respectively, which is remarkably higher than that of the conventional anode materials (such as graphite and TiO2). Ab initio molecular dynamics simulations confirm the room-temperature stability of the alpha-SiX monolayers at the maximum loading of Li atoms. The lower diffusion energy barriers of 0.30 eV (for alpha-SiN monolayers) and 0.16 eV (for alpha-SiP monolayers) ensure good diffusivity of ions over monolayers. The calculated open-circuit voltage is also favorable for battery applications. The aforementioned findings suggest that the alpha-SiX monolayers could be beneficial and compelling host anode material for high-performance LIBs.

Automated summary

Density functional theory simulations were used to investigate the properties of α-SiX (X = N, P) monolayers as anode materials in LIBs. The results showed that α-SiX monolayers have excellent stability and can adsorb Li atoms, converting into a metallic state and enabling high storage capacity and good diffusivity. These findings suggest that α-SiX monolayers have potential applications as host anode materials for high-performance LIBs.