C ₄ BN: A Novel 2D Boron–Carbon–Nitride Monolayer for High-Performance Potassium-Ion Batteries

Inspired by recent advances in the synthesis of two-dimensional (2D) carbon-based materials and their promising applications in green sustainable energy, this study systematically explored various boron, nitrogen, and their codoped C63 structures from a theoretical perspective. Ultimately, C4BN was identified as the most promising novel boron–nitrogen codoped 2D carbon-based material. Density functional theory (DFT) calculations reveal that the C4BN monolayer exhibits not only excellent structural stability and mechanical properties but also favorable electronic and electrochemical characteristics. As an anode material for potassium-ion batteries (KIBs), its theoretical specific capacity reaches 735.78 mAh/g, significantly outperforming many reported two-dimensional materials for KIBs. It simultaneously exhibits a low open-circuit voltage (0.33 V) and fast potassium-ion diffusion, with a diffusion barrier as low as 0.12–0.13 eV. These advantages highlight the great potential of C4BN for high-performance KIB anode applications and provide valuable insights for the design and prediction of new two-dimensional materials.