Na3Zr2Si2PO12 solid-state electrolyte with glass-like morphology for enhanced dendrite suppression

Rechargeable batteries based on solid-state electrolytes are of great interest and importance for the next-generation energy storage due to their high energy output and improved safety. For building the solid-state batteries, Na3Zr2Si2PO12 (NZSP) represents a promising candidate as it features high chemical stability against air exposure and a high Nat conductivity. NZSP pellets were usually calcined at a high temperature, and the high volatility of Na and P elements easily led to the formation of impurity phase. In this work, the effects of calcination temperature and stoichiometry on the phase purity and ionic conductivity of the NZSP electrolyte were studied. At an elevated sintering temperature, the NZSP electrolyte showed a high ionic conductivity owing to decreased porosity, and the highest ionic conductivity at 30 degrees C was observed to be 2.75 x 10(-5) S.cm(-1) with an activation energy of 0.41 eV. For the stoichiometry, the introduction of 5 mol% excessive P results in formation of more Na3PO4 and glass-like phase at the grain boundary, which caused the blurred grain boundary and reduced grain barrier, and effectively suppressed Na dendrite growth, then accounted for improved cycling performance of a NallNa symmetric cell. Our work provided insights on reasonable design and preparation of NZSP electrolyte towards practical realization of solid-state Na-metal batteries.