First-Principles Investigation of Naphyne as an Ultra-High-Capacity Anode Material for Potassium-Ion Battery

Potassium-ion batteries (KIBs) are gaining attention as a cost-effective and sustainable alternative to lithium-ion batteries, primarily due to the natural abundance of potassium and its favorable electrochemical characteristics. Despite these advantages, the development of highly efficient anode materials remains a significant challenge, mainly because of the large ionic radius of the K+ ion, which tends to induce structural instability in conventional anode materials. In this context, we employ first-principles calculation based on density functional theory (DFT) to evaluate the potential of naphyne, a novel two-dimensional (2D) polyaromatic alkyne-based carbon structure, as a high-performance anode material for KIBs. Our computational analysis reveals that naphyne offers an ultrahigh theoretical capacity of 1487.53 mAh/g, significantly outperforming conventional anodes like graphite (273 mAh/g) and other reported anode materials. This superior theoretical storage capability arises from its ability to stably accommodate up to 48 potassium ions in the K48C72 unit via multilayer adsorption, with average adsorption energies ranging from −0.881 to −0.133 eV per adsorbed K-ion. Moreover, naphyne exhibits a low potassium-ion diffusion barrier (0.37 eV) and high diffusion coefficient (up to 5.502 × 10–7 cm2/s), supporting rapid K-ion transport and excellent rate capability. The structure undergoes minimal structural deformations (≤0.65% along a, ≤ 0.73% along b and ≤ 1.38% area expansion) upon potassiation, indicating robust structural stability under cycling conditions. Notably, potassium adsorption also induces a transition in the electronic structure from semiconducting to metallic behavior, thereby enhancing the material’s electronic conductivity and facilitating fast charge transfer. With an average low open-circuit voltage (OCV) of approximately 0.37 V, naphyne presents a balanced electrochemical profile suitable for high energy density storage. Collectively, these findings highlight naphyne as a promising and transformative anode material for the advancement of next-generation, sustainable potassium-ion battery technologies.