M-graphene: A metastable two-dimensional carbon allotrope

Ever since the exfoliation of graphene, two-dimensional (2D) atomic layers derived from bulk materials have received significant attention because of their fascinating properties, as well as their potential for technological applications. In this work, a metastable planar 2D carbon allotrope composed of 5 + 7 rings (dubbed M-graphene) was predicted via an unbiased crystal structure prediction algorithm based upon the particle swarm methodology and studied via first-principles calculations. Computations show that M-graphene is not only dynamically stable, but it can also withstand temperatures as high as 2000 K. Our simulations reveal that it is a promising candidate as an anode material for Li-ion batteries (LIBs), because of the relatively low diffusion energy barrier of Li (0.338 eV), open-circuit potential (0.029 V) and high lithium-storage capacity (279 mAh g^-1). This work may be useful for designing novel 2D carbon-based materials.