AlC2 monolayer and AlC2/graphene heterostructure as high-performance anode materials for sodium-ion batteries: A first-principles study

Two-dimensional monolayers of group III (e.g., borophene, aluminene) and group IV (e.g., graphene) elements face challenges as sodium-ion battery (SIB) anodes due to their inherent structural instability and chemical inertness, respectively. To overcome these limitations, we proposed a stable aluminum dicarbide (AlC 2 ) monolayer, designed to combine the advantageous properties of both graphene and aluminene. Monolayer AlC 2 exhibits intrinsic metallicity and exceptional performance as an anode material for SIBs, featuring a low diffusion barrier (0.40 eV), a suitable average open-circuit voltage (0.25 V), and a high storage capacity (1577 mAh g −1 ). Furthermore, we constructed a graphene/AlC 2 van der Waals heterostructure to enhance electrochemical performance, which not only strengthens Na adsorption on graphene but also improves ionic diffusivity on the AlC 2 layer. These findings demonstrate that AlC 2 is a highly promising material for next-generation energy storage systems. • AlC 2 maintains high conductivity while significantly enhancing substrate oxidation resistance. • AlC 2 offers high capacity (1577 mAh g −1 ), low barrier (0.4 eV), and stable voltage (0.25 V). • Graphene/AlC 2 enables Na adsorption on graphene with fast diffusion at the interface.