First principles study of alkali and alkaline earth metal ions adsorption and diffusion on penta-graphene

Developing carbon based anode materials for alkali and alkaline earth metal ion batteries is important for the development of non-Li metal ion batteries. From density functional theory calculations, we studied alkali metal (Li, Na, K, and Rb) and alkaline earth metal (Be, Mg, Ca, Sr, and Ba) ions adsorption on penta-graphene (PG), which is a novel two dimensional (2D) carbon isomer composed of both sp(2) and sp(3) hybridized C-atoms. Strong correlations are observed between the adsorption energy and the electronegativity of the M-atoms, namely, smaller electronegativity corresponds to lower adsorption energy. The suitable Ca-ion intercalation potential (similar to 117 mV), metallic electronic structures of Ca-ion adsorbed PG, low Ca-ion diffusion energy barriers (0.36 eV to 0.51 eV), and high specific capacity (1487.6 mAh/g) suggest that PG can be applied as an excellent anode material for Ca-ion batteries.