A comprehensive exploration of Na⁺ ion transport in NaSICONs using molecular dynamics simulations

Scandium-substituted Na_{1+<i>x</i>+<i>y</i>} Sc _<i>y</i> Zr_2-<i>y</i> Si _<i>x</i> P_3-<i>x</i> O₁₂ NaSICONs have emerged as promising electrolyte materials for all-solid-state sodium batteries. However, the comprehensive investigation of these multi-element structures is challenging due to their vast compositional space, leading to a limited number of compositions explored thus far. In this study, we address this issue by employing low-cost, yet high-precision force field molecular dynamics simulations based on density functional theory to investigate the Na⁺ mobility and resulting conductivity in Na_{1+<i>x</i>+<i>y</i>} Sc _<i>y</i> Zr_2-<i>y</i> Si _<i>x</i> P_3-<i>x</i> O₁₂ (0 ≤ <i>x</i> ≤ 3; 0 ≤ <i>y</i> ≤ 2). Our findings show that the incorporation of Sc³⁺- and Si⁴⁺-substituents enhances the conductivity, achieving values of 10^-2 S cm^-1 at room temperature for moderate to high substitution degrees. Moreover, our study demonstrates the efficacy of the applied methodology for large-scale screening, enabling the exploration of extensive configurational spaces of NaSICONs and other materials for potential use as solid-state electrolytes.