Ab-initio investigation of carbon-doped χ3 borophene for Na and K storage as post lithium-ion batteries

Abstract

Reducing pollution problems caused by fossil fuels requires providing advanced solutions for storing clean energy. Today, rechargeable lithium-ion batteries (LIBS) are an integral part of energy storage technologies. But, due to the problems caused by lithium sources, the need to replace them is felt more than ever. Among emerging alternatives to LIBs, sodium and potassium ion batteries (SIBS and PIBS) stand out due to their natural abundance and economic efficiency. This study explores χ3 borophene as a high-performance anode material for SIBs and PIBs through density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. The results reveal that carbon-doped χ3 borophene demonstrates a metallic characteristic, ensuring high electrical conductivity. AIMD calculations indicate that the material has structural stability at 300 K. With ultralow diffusion energy barriers of 0.22 eV and 0.14 eV for Na, and 0.11 eV and 0.09 eV for K, enabling efficient ion mobility that is vital in fast charging technology. Notably, it delivers a high theoretical storage capacity of 822 mAhg⁻¹ for both Na and K, coupled with competitive open-circuit voltages of 0.72 V (Na) and 1.36 V (K). AIMD simulations further validate its thermal stability under full Na and K adsorption at 300 K. These outstanding properties establish carbon-doped borophene as a robust and high-performance anode candidate for future alkali metal-ion battery technologies.