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 C 63 structures from a theoretical perspective. Ultimately, C 4 BN was identified as the most promising novel boron–nitrogen codoped 2D carbon-based material. Density functional theory (DFT) calculations reveal that the C 4 BN 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 C 4 BN for high-performance KIB anode applications and provide valuable insights for the design and prediction of new two-dimensional materials.