Metallic Si₂BC Monolayers as High-Performance Anode Materials for Potassium-Ion Batteries

Potassium-ion batteries (KIBs) are gaining attention as potential next-generation energy storage devices. Nonetheless, the commercialization of KIBs has been hindered by a lack of high-performance anode materials. In this study, we introduce a multielement combination strategy to modulate the structure and surface charge of two-dimensional materials, considering the competitive bonding interactions and charge transfer between atoms. Through structural search calculations, we uncover a Si₂BC monolayer, which exhibits three distinct types of π-bonding strength. This material demonstrates excellent structural stability, intrinsic metallicity, and superior electrochemical performance. Specifically, the Si₂BC monolayer shows a remarkably low K-ion migration barrier of just 0.10 eV, a theoretical capacity peaking at 1696.55 m Ah/g, and an average open-circuit voltage of 0.72 V, which position it as a highly promising candidate for applications as an anode in KIBs. Notably, we discover that the strength of the π-bonds within the Si₂BC monolayer is inversely related to the K-ion migration barriers, with stronger π-bonds facilitating lower migration barriers and optimizing ion mobility. This finding provides valuable insights into the role of bond strength in enhancing ion transport.