Highly uniform nitride-rich artificial solid electrolyte interphase enabled by nano-silicon nitride for superior performance in advanced sodium metal batteries

Abstract

Sodium-metal batteries, notable for their high energy density and cost-effectiveness, face significant challenges such as dendritic sodium formation and unstable solid-electrolyte interphase (SEI), which hinder their operational safety and efficiency. Navigating through these challenges inherent in sodium-metal batteries, this research innovates by leveraging silicon nitride (Si₃N₄) to forge a robust sodium nitride (Na₃N)-rich artificial SEI layer. The Na₃N-rich SEI layer offers advantages such as improved mechanical stability and enhanced ionic conductivity, contributing to the overall performance of the battery. Through a cost-effective and straightforward methodology, the study showcases that optimized concentrations of 3 wt% micro-Si₃N₄ and 1 wt% nano-Si₃N₄ enhanced cycling stability and diminished overpotentials. Although the micro-Si₃N₄ extends the sodium-metal symmetric cells' life to over 700 hours at 0.25 mA cm⁻² in carbonate-based organic electrolytes, the nano-Si₃N₄ variant excels, pushing the boundary to over 1100 hours, primarily due to its superior ability to form a highly uniform and dense SEI layer. These critical advancements, inhibiting dendrite growth and minimizing unnecessary SEI formation, signal a leap forward in developing safer, more resilient sodium metal battery technologies.