Fast Na-diffusive tin alloy for all-solid-state Na-based batteries

Abstract

All-solid-state Na batteries, which are inexpensive and highly stable, are promising candidates for energy storage in environmentally friendly microgrids and vehicles. Na diffusivity is an important parameter for the performance of these batteries. In this study, we found that the metastable phase Na₁₀Sn₄ exhibits fast Na diffusivity (room temperature diffusion coefficient D₂₅ = 5.4 × 10⁻⁷ cm² s⁻¹), surpassing that of other reported alloys (Sb- and Ge-alloys) as well as oxide and sulfide materials. Na₁₀Sn₄ was synthesised by a mechanochemical method, and its electrode properties were evaluated for an all-solid-state battery. The cell exhibited an interfacial resistance of 100.1 Ω cm², which is smaller than those reported between metallic anodes and solid or liquid electrolytes. These results indicate that Na₁₀Sn₄ has significant potential as an ultra-low-resistance electrode to improve all-solid-state Na batteries, which is a major step forward in energy storage material research.