Nanomaterials, Vol. 15, Pages 1268: Diffusion of Alkaline Metals in Two-Dimensional β1-ScSi2N4 and β2-ScSi2N4 Materials: A First-Principles Investigation
Nanomaterials doi: 10.3390/nano15161268
Authors:
Ying Liu
Han Fu
Wanting Han
Rui Ma
Lihua Yang
Xin Qu
The MA2Z4 family represents a class of two-dimensional materials renowned for their outstanding mechanical properties and excellent environmental stability. By means of elemental substitution, we designed two novel phases of ScSi2N4, namely β1 and β2. Their dynamical, thermal, and mechanical stabilities were thoroughly verified through phonon dispersion analysis, ab initio molecular dynamics (AIMD) simulations, and calculations of mechanical parameters such as Young’s modulus and Poisson’s ratio. Electronic structure analysis using both PBE and HSE06 methods further revealed that both the β1 and β2 phases exhibit metallic behavior, highlighting their potential for battery-related applications. Based on these outstanding properties, the climbing image nudged elastic band (CI-NEB) method was employed to investigate the diffusion behavior of Li, Na, and K ions on the material surfaces. Both structures demonstrate extremely low diffusion energy barriers (Li: 0.38 eV, Na: 0.22 eV, K: 0.12 eV), indicating rapid ion migration—especially for K—and excellent rate performance. The lowest barrier for K ions (0.12 eV) suggests the fastest diffusion kinetics, making it particularly suitable for high-power potassium-ion batteries. The significantly lower barrier for Na ions (0.22 eV) compared with Li (0.38 eV) implies that both β1 and β2 phases may be more favorable for fast-charging/discharging sodium-ion battery applications. First-principles calculations were applied to determine the open-circuit voltage (OCV) of the battery materials. The β2 phase exhibits a higher OCV in Li/Na systems, while the β1 phase shows more prominent voltage for K. The results demonstrate that both phases possess high theoretical capacities and suitable OCVs.
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Ying Liu www.mdpi.com
