Two-dimensional metallic TPHOD-graphene: surface and interface engineering toward a high-performance anode material for potassium-ion batteries

Potassium-ion batteries (PIBs) show great promise as an attractive alternative to lithium-ion batteries (LIBs), owing to their affordability, safety, and high energy density. However, the lack of suitable anode materials poses a significant challenge to realize high-performance PIBs. By the assembly of acenaphthene (C₁₂H₈) skeletons, we predict a two-dimensional (2D) carbon allotrope named TPHOD-graphene, which is composed of tetragonal, pentagonal, hexagonal, octagonal, and dodecagonal rings. It has excellent dynamical, thermal, and mechanical stability. The metallic nature of the TPHOD-graphene monolayer contributes to excellent conductivity, facilitating rapid electron transport. As an anode material for PIBs, TPHOD-graphene delivers a high theoretical capacity of 930 mAh/g. The low ion diffusion barrier (0.33–0.37 eV) favors good charge-discharge efficiency. Moreover, the moderate intercalation/deintercalation potential effectively mitigates the formation of metal dendrites. The introduction of solvents can boost the adsorption and mobility of K ion on TPHOD-graphene. Furthermore, the presence of vacancy in TPHOD-graphene significantly enhances the K adsorption strength but creates a trapping effect which impedes ion migration. Similar to the monolayer, bilayer TPHOD-graphene maintains the good adsorption and diffusion characteristics of K.