Designing Glass Nanocomposites with Nonbridging Oxygen Defects: An Approach to Improve Sodium-Ion Conduction

Samarium-doped glass nanocomposites were synthesized following the sol–gel process employing mesoporous alumina as a template. A series of nanocomposites comprising a nanoglass composition were designed by tuning the ratio of Sm/Si. Modern characterization methods were employed to conduct extensive microstructural investigations. Comprehensive XPS studies were used to probe the underlying mechanism of nonbridging oxygen defects in promoting Na-ion dynamics. Optical absorption and FTIR investigations were employed to understand the structural disorder with its influence on ion migration and reduction of the activation energy. Using temperature-dependent impedance spectroscopy, the impact of the structural morphology on the alkali-ion mobility was investigated. The higher room-temperature ionic conductivity (∼5.2 × 10–5 S cm–1) and lower activation energy (0.08 eV) are mostly attributed to the nonbridging oxygen defect. When operated over 250 cycles, galvanostatic charge–discharge cycles showed a retentive capacity of around 82.4% and a maximum specific capacitance value of approximately 86.2 mAh/g. Our findings on structural engineering of nanosilicate glass through rare-earth additives open the possibility to engineer porous glass-based electrodes for sodium battery application.