Crystallization of amorphous Na2Si2O5 as a Na-ion conductor

The Na2Si2O5 in the amorphous state exhibits a fast Na+-conduction at elevated temperatures. However, it is metastable, gradually transforming into the insulating Na2Si2O5 in the crystalline state with temperatures. The present work shows that the presence of H2 and Al-doping can suppress the harmful amorphous-to-crystalline transformation in Na2Si2O5. A systematic investigation was carried out to understand the fundamental aspects of the amorphous-to-crystalline transformation through a suite of advanced experimental techniques including X-ray diffraction (XRD), differential scanning calorimetry (DSC) analysis, electrochemical impedance spectroscopy (EIS), Raman spectroscopy and multi-nucleus nuclear magnetic resonance spectroscopy (NMR).