ψ-Graphene: A New Metallic Allotrope of Planar Carbon with Potential Applications as Anode Materials for Lithium-Ion Batteries.

Using state-of-the-art first-principles calculations, we propose a new two-dimensional (2D) carbon allotrope constructed by polymerizing the carbon skeletons of s-indacenes, named PSI (ψ)-graphene. We show that ψ-graphene has the lowest energy among all hitherto reported 2D allotropes of carbon composed of 5-6-7 carbon rings and is dynamically and thermally stable. This structure is metallic with robust metallicity against external strain. In addition, we find that the adsorption of Li atoms on ψ-graphene is exothermic, and the diffusion energy barrier is low and comparable to that of graphene. Furthermore, ψ-graphene can achieve a maximum Li storage capacity equivalent to that of LiC6, suggesting its potential as an anode material for Li-ion batteries (LIBs). In addition, we show that increasing the number of hexagons in this structure can enhance the thermodynamic stability of the sheet while maintaining its metallicity. This study provides new insights into the design of new metallic carbon for nanostructured anode materials in the next generation of LIBs.