Investigating the Influence of Sintering Temperature and Ascertaining Hopping Path in Sodium Superionic Conducting Electrolytes for Sodium-Ion Batteries

Recently, sodium super-ionic conducting (NASICON) type solid electrolytes have gained significant interest as potential candidates for next-generation batteries due to their exceptional properties such as high ionic conductivity, affordability, and remarkable chemical and electrochemical stability. Therefore, NASICON type solid electrolyte (Na 3 Zr 2 Si 2 PO 12 ) is synthesized by solution assisted-solid state reaction (SA-SSR) method and sintered at three different temperatures, 1200 ℃, 1250 ℃ and 1300 ℃. Various experimental techniques are used to characterize and optimize the sintered electrolytes. The Rietveld refinement of X-ray diffraction pattern of prepared electrolytes revealed the monoclinic crystal structure having 3-dimension hopping channel for sodium ion migration through triangular bottleneck area. Complex impedance spectroscopy revealed, the highest bulk and grain boundary conductivity are found, 4.05 mS cm -1 and 0.31 mS cm -1 , respectively, for the sample sintered at 1250 ℃. Using optimized electrolyte, sodium half-cell is demonstrated with Na 3 V 2 P 3 O 12 (NVP) as cathode. The assembled cell delivers maximum discharge capacity 101.6 and 84.45 mAh g -1 at the current density 10 and 40 mA g -1 , respectively with good capacity retention (~95.02%) upto 50 cycles.