Elucidating the influence of structure and Ag+-Na+ ion-exchange on crack-resistance and ionic conductivity of Na3Al1.8Si1.65P1.8O12 glass electrolyte

Glasses are emerging as promising and efficient solid electrolytes for all-solid-state sodium-ion batteries. However, they still suffer from poor ionic conductivity and crack-resistance, which need to be improved for better battery performance, reliability, and service life. The current study shows a significant enhancement in crack resistance (from 11.3 N to 32.9 N) for Na ₃Al _1.8Si _1.65P _1.8O ₁₂ glass (Ag-0 glass) upon Na ⁺-Ag ⁺ ion-exchange (IE) due to compressive stresses generated in the glass surface while the ionic conductivity values (∼10 ⁻⁵ S/cm at 473 K) were retained. In this study, magic angle spinning-nuclear magnetic resonance (MAS-NMR), molecular dynamics (MD) simulations, Vickers micro hardness, and impedance spectroscopic techniques were used to evaluate the intermediate-range structure, atomic structure, crack resistance and conductivity of the glass. MAS-NMR and MD simulations confirm the presence of Si‒O‒Al‒O‒P groups in the glass, thus enabling formation of Na percolated channel regions. AC-conductivity analysis for Ag-0 and ion-exchanged Ag-0 glass suggests that the mobility of Na ⁺ ion increases with increasing temperature. It is observed that the measured mean square displacement ( 〈 R 2 ( t p ) 〉 ) for sodium cations using AC-conductivity isotherms is nearly constant up to 448 K and then increases with increasing temperature up to 523 K. From the impedance spectra for ion-exchanged Ag-0 glass, it is identified that the increase in 〈 R 2 ( t p ) 〉 and thereby, the mobility of sodium-ions for Ag-0 glass is due to the structural variations in the Ag-0 glass with increasing the temperature. Overall, the mechanisms presented in this article helps in formulating better glass based electrolyte materials for room temperature or high temperature sodium-ion batteries.