Theoretical prediction of metallic R12-graphene as a promising anode material for potassium-ion batteries with high ion mobility, high capacity, and excellent electrolyte wettability

Although graphene has excellent electrical and mechanical properties, the giant delocalized π-electron system makes it chemically inert. Here, we propose an idea to design two-dimensional (2D) carbon allotropes via incorporating multiple rings in sp2-hybridized carbon networks, which can break the π-bonding network and enhance the surface reactivity. By assembling molecule of cyclobut(a)acenaphthylene, we predict a monolayer 2D carbon material, named as R12-graphene, which is composed of quadrilateral, pentagonal, hexagonal, and dodecagonal carbon rings. It shows great stability in energetic, dynamic, thermodynamic, and mechanical aspects. It exhibits high-performance as an anode material for potassium-ion batteries (PIBs), including an intrinsic metallic behavior, a high theoretical capacity (632 mA h g−1), a low K diffusion barrier (0.33 eV), and a low average open-circuit voltage (0.5 V). The presence of electrolytes can provide better K ion adsorption and diffusion capability compared to that in vacuum. Furthermore, R12-graphene has excellent wettability toward some commonly used electrolytes, which is beneficial for improving the charge/discharge rate for PIBs.