Comprehensive Insight into the Synthesis, Structure, Stability, and Ionic Conductivity of Na5MSi4O12 type Solid Electrolytes for Solid-State Sodium Batteries

Abstract

Na5MSi4O12 -type silicates are emerging as functional solid electrolytes for solid-state sodium batteries due to their high ionic conductivity, combined with excellent chemical and electrochemical stability and low electronic conductivity. Understanding their synthesis, phase stability, crystal and electronic structures, and ionic conductivity and diffusion is essential for designing and developing better compounds. To this end, we investigated the synthesis, phase stability, structure, ionic and electronic conductivities, chemical and electrochemical stability, interfacial resistance, and Na metal deposition of four highly conducting solid electrolytes in the Na5MSi4O12 series (Na5YSi4O12 , Na5DySi4O12, Na5GdSi4O12, and Na5SmSi4O12 ). By analysing the results from synchrotron XRD, in situ high-temperature XRD, simultaneous thermal analysis, SEM, high-temperature electrochemical impedance spectroscopy, electronic structure calculations, chronoamperometry, and chronopotentiometry, we sought to establish correlations among these phases. This article will provide deep insight into the properties of NMS-type compounds.