B4CN3 monolayer as a promising high-capacity and fast-ion-diffusion anode for Li-, Na-, and K-ion battery

The development of high-capacity and fast-charging anode materials is crucial for next-generation alkali metal-ion batteries. Herein, first-principles calculations were performed to investigate the potential of a novel two-dimensional B 4 CN 3 monolayer as an anode material for Li-, Na-, and K-ion batteries. The results show that B 4 CN 3 possesses good dynamical, thermodynamic, and mechanical stability, together with an intrinsic narrow band gap of 0.36 eV. Li, Li, Na, and K atoms preferentially adsorb at the H1 site, exhibiting adsorption energies of −3.50, −2.73, and −3.12 eV, respectively. With increasing ion coverage, the B 4 CN 3 monolayer undergoes a semiconductor-to-metal transition, which is beneficial for electronic transport during battery operation. The maximum theoretical specific capacities are calculated to be 1241, 1103, and 827 mAh g −1 for Li, Na, and K storage, respectively, accompanied by average open-circuit voltages of 0.16, 0.57, and 0.39 V. Furthermore, the diffusion barriers of Li, Na, and K ions are only 0.26, 0.05, and 0.03 eV, indicating favorable ion migration kinetics. These results suggest that the B 4 CN 3 monolayer is a promising anode candidate for alkali metal-ion batteries and provides insights into the design of high-performance B–C–N-based energy-storage materials.