A New Class of Carbonate-Oxychloride Solid Electrolytes for High-Performance Sodium-Ion All-Solid-State Batteries

As a key component of sodium-ion all-solid-state batteries (ASSBs) with promising high safety and energy density, solid-state electrolytes (SSEs) play a critical role in determining electrochemical performance. However, current synthesis methods for high-performance SSEs still leave room for improvement. This study introduces a series of novel amorphous sodium-ion SSEs (MCly-xNa2CO3, M = Ta, Nb, Hf, Zr, and Al) synthesized efficiently via high-energy ball milling. We obtained the TaCl5-1.2Na2CO3 SSE with an impressive room temperature (RT) ionic conductivity of 1.11 mS cm-1 in just 10 minutes. Furthermore, the optimal Na+ conductivity of TaCl5-0.5Na2CO3 (TC-NCO) can reach 5.01 mS cm-1. Local structure features Ta-centered polyhedra, either isolated or connected by bridging oxygens, dispersed within a disordered amorphous matrix that facilitates Na+ transport. TC-NCO SSE exhibits high-voltage stability (4.24 V vs. Na15Sn4) and compatibility with various cathodes in ASSBs. When paired with an O3-type oxide cathode, it retains 92% capacity after 300 cycles at 0.5 C. The findings enable the rapid synthesis of high-performance sodium-ion SSEs, contributing to the advancement of ASSBs.