Two-dimensional azulenoid kekulene-based metallic allotropes for energy storage applications

Abstract

Search for new metallic materials comprising lighter mass elements such as carbon is of present interest in battery science and technology. Inspired by the exceptional porosity and intrinsic conductivity of recently reported azulenoid kekulene-based structures [Nat.Commun. 2024, 15, 1953], we explored their two metallic allotropes AKC-5,0 and AKC-3,2, regarding stability (dynamic, thermal, and chemical), electronic properties, and electrochemical performance as anode materials. Based on first-principles calculations, we investigate that AKC-5,0/AKC-3,2 presents several strong binding sites for sodium ions which enable it to demonstrate a superhigh theoretical capacity of 1458/1880 mA h g⁻¹, a low average voltage of 0.48/0.34 V and small diffusion barriers of 0.16/0.15 eV respectively. In addition, we examine AA-stacking for both allotropes and investigate their effects on the performance parameters for SIBs. The super high storage capacity and intrinsic conductivity together with a small diffusion barrier suggest that these metallic azulenoid kekulene monolayers are very promising for sodium-ion batteries.