First-principles study of dual-doped graphene: towards promising anode materials for Li/Na-ion batteries

Two-dimensional materials as electrodes have significant potential in energy storage and conversion and can address the issues related to battery technologies. Accordingly, first-principles calculations were executed to search for the best possible anode material for Li/Na ion batteries. Three families of dual-doped graphene (DDG) including Be-B, BeN, and BeO were studied because it is easier to synthesize DDG instead of its mono-doped counterpart. Among them, Be-B DDG was found to be the most promising since it can cause a massive increase in the adsorption of Li (2.33 eV, by 3.1 times) and Na (2.24 eV, by 4.3 times) at the vdW-DF/DZP level of theory. The integration of these ions caused the structures to become metallic, resulting in good electronic conductivity, which is essential for anode materials. Furthermore, Be-B DDG exhibited an average open circuit voltage of 2.34 V (1.3* V) and 1.82 V (1.02* V) for Li and Na, respectively, when the energy of the isolated gas-phase (* represents the energy of one atom taken from the bulk) is used for Li and Na. This modest average open circuit voltage of 1.3* V for Li is in the range of that of the most commonly used graphite-Li (0.11 V) and TiO2-Li (1.5-1.8 V). Moreover, the negligible percentage change in the plane of Be-B DDG during the intercalation of Li/Na ensured good cyclic stability. Additionally, the exceptional storage capacities of 2334 mA h g(-1) for Li and 1012 mA h g(-1) for Na with an open circuit voltage of 0.23* V and 0.25* V, respectively, shows that Be-B DDG has potential as a remarkable anode material for LIBs and SIBs.