New Findings on an Old Question: Can Defect‐Free Graphene Monolayers be Superior Metal‐Ion Battery Anodes?

Abstract Graphene has numerous extraordinary properties and applications, ranging from water purification to energy storage. Previous studies identified that defect‐free graphene monolayers cannot be adopted as lithium‐ion battery anodes. Approaches, such as functionalization and introducing defects in graphene, have been employed to improve its performance in energy storage. However, defects in graphene boost dendrite growth, resulting in safety issues and fast power losses in batteries. Herein, by adopting state‐of‐the‐art first‐principles calculations, orbital theory, and transition state theory, it is found that defect‐free graphene monolayers are a promising potassium‐ion battery (KIB) anodes, however, they cannot be employed as lithium‐/sodium‐/magnesium‐/calcium‐/zinc‐/aluminum‐ion battery anodes. The evidence of adsorption energy and electron transfer indicates that van der Waals interactions dominate the adsorption of K atoms while delocalized electrons neutralize repulsion between K ions. The KIB anode delivers a high capacity of 1487.7 mA h g⁻¹ and ultrafast charging/discharging rates. Transition state theory results demonstrate that its ultrahigh classic diffusion constants achieve 2.36 × 10¹¹/1.55 × 10⁹ s⁻¹, its Wigner zero‐point‐energy‐/tunneling‐corrected diffusion constants approach 2.38 × 10¹¹/1.56 × 10⁹ s⁻¹, and its low quantum‐mechanical tunneling effects are 0.67%/0.72% under the low/high concentration diffusion of K ions at room temperature. This work offers a more comprehensive understanding of defect‐free graphene.