Superflexible C68-graphyne as a promising anode material for lithium-ion batteries

Abstract

The breakthrough in the synthesis of graphyne, graphdiyne and graph-4-yne stimulates interest in studying new members of the graphyne family for promising applications. In this work, a new allotrope of graphyne with excellent stability and an ultrahigh specific surface area of 4255 m² g⁻¹, named C₆₈-graphyne, is predicted by first principles calculations. Mechanical tests reveal that C₆₈-graphyne exhibits much smaller in-plane tensile stiffness (∼50.5 N m⁻¹) and out-of-plane bending stiffness (∼0.5 eV) than graphene (in-plane tensile stiffness 350 N m⁻¹ and out-of-plane bending stiffness 1.4 eV), suggesting C₆₈-graphyne as a superflexible material. Meanwhile, our results show that monolayer C₆₈-graphyne is a semiconductor with a direct band gap of 1.0 eV, which can be tuned by strain-engineering, and the calculated carrier mobility is as high as 1.81 × 10⁵ to 2.97 × 10⁵ cm² V⁻¹ s⁻¹ at 300 K. Finally, the potential application of C₆₈-graphyne as an anode material for lithium-ion batteries is explored and predicted. The calculated results show highly efficient charge transfer from the adsorbed Li ions to C₆₈-graphyne yet a low diffusion barrier for Li ions in C₆₈-graphyne for fast charge/discharge rates. The storage capacities for Li in monolayer and bilayer C₆₈-graphyne are calculated to be as high as 1954 and 1675 mA h g⁻¹, respectively. These features make C₆₈-graphyne a promising anode material for lithium-ion batteries with excellent energy storage capacities as well as fast charge/discharge rates.