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 H-2 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). (C) 2016 Elsevier B.V. All rights reserved.