Dynamic Study of Superionic Sodium-Ion Transport in Amorphous Sodium-Tantalum-Oxychloride Electrolytes

Amorphous solid electrolytes offer promising solutions for safe, high-performance sodium-ion batteries, thanks to their isotropic ion transport and mechanical flexibility. Here we use ab initio molecular dynamics (AIMD) to investigate the Na-ion superionic transport behavior in amorphous sodium-tantalum-oxyhalide electrolytes, focusing on the relationship between local structure and ionic conductivity. Our simulations of the optimized NaTaOCl₄ yielded a high room-temperature ionic conductivity of 21.75 mS·cm^-1, which is higher than the experimental benchmarks by approximately four times. We identify a dual-anion synergistic mechanism: nonbridging oxygen acts as a stable hopping site, and Cl-ion vibrations facilitate rapid Na⁺ migration. The AIMD simulations predict an activation energy of 0.15 eV for the Na-ion, which is half that of crystalline counterparts, and reveal that deviations in effective nonbridging oxygen content raise diffusion barriers. These findings clarify the role of oxychloride chemistry in enhancing ion mobility and provide rational design principles for next-generation oxychloride solid electrolytes.