Revealing Na⁺ Dynamics in the Na₄Sn₂Ge₅O₁₆ Solid Electrolyte Material Using ²³Na Solid-State NMR Spectroscopy and...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Electrochemistry

Background:

• All-solid-state sodium-ion batteries (ASSNIBs) require efficient sodium-ion (Na+) conductors.
• Na4Sn2Ge5O16 is a novel material with potential for ASSNIB applications.
• Understanding Na+ dynamics is crucial for optimizing ionic conductivity.

Purpose of the Study:

• To investigate the Na+ dynamics in the Na4Sn2Ge5O16 solid electrolyte.
• To elucidate the behavior of Na+ ions at different crystallographic sites.
• To establish a molecular-level understanding of Na+ transport mechanisms.

Main Methods:

• Solid-state 23Na Nuclear Magnetic Resonance (ssNMR) spectroscopy at multiple magnetic field strengths (7, 11.7, and 20 T).
• Relaxation studies and 1D/2D 3QMAS 23Na NMR.
• Density Functional Theory (DFT)-based CASTEP calculations and EXPRESS script simulations.

Main Results:

• Distinct Na+ dynamics were observed for the immobile Na1 sites and dynamically mediated Na2-3 sites.
• DFT calculations accurately reproduced experimental lineshapes for the Na1 site.
• An exchange rate of 2 × 10^5 Hz was estimated for the fast-exchanging Na2-3 sites.

Conclusions:

• The study provides detailed insights into the Na+ dynamics within Na4Sn2Ge5O16.
• The combination of experimental NMR and computational methods enables accurate characterization of ion transport.
• This work lays the foundation for designing advanced solid electrolytes for next-generation sodium-ion batteries.