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.