First-principles investigation of Janus SVSiN₂ and SVSiP₂ two-dimensional materials as high-performance anodes for Li- and Na-ion batteries

Despite substantial progress in battery component engineering, the development of advanced electrode materials that can deliver high capacity, fast ion transport, and excellent structural stability remains a major challenge for next-generation alkali-ion batteries. In this work, first-principles calculations were performed to systematically investigate the potential of Janus SVSiN₂ and SVSiP₂ monolayers as 2D anode materials for Li- and Na-ion batteries. Both materials demonstrate outstanding structural, dynamical, and thermal stability, evidenced by the absence of imaginary frequencies in the phonon spectra and by ab initio molecular dynamics simulations performed at 500 K for 5 ps. The theoretical specific capacities reached high values of 889.5 and 580.4 mAh g−1 for Li and Na storage, respectively, on SVSiN₂, and 749.02 and 517.09 mAh g−1 for SVSiP₂. The calculated open-circuit voltages were within an ideal anode range, with average values of 0.25 and 0.26 V for Li, and 0.10 and 0.44 V for Na on SVSiN₂ and SVSiP₂, respectively. The monolayers demonstrate favorable ion transport kinetics, with ultra-low diffusion barriers of 0.021 and 0.266 eV for Li, and 0.04 and 0.19 eV for Na on SVSiN₂ and SVSiP₂. The findings highlight the significant potential of the monolayers as high-performance anode materials.